WO2012027619A1

WO2012027619A1 - Boost charge-pump with fractional ratio and offset loop for supply modulation

Info

Publication number: WO2012027619A1
Application number: PCT/US2011/049243
Authority: WO
Inventors: Nadim Khlat
Original assignee: Rf Micro Devices, Inc.
Priority date: 2010-08-25
Filing date: 2011-08-25
Publication date: 2012-03-01
Also published as: WO2012027619A4

Abstract

Embodiments disclosed in the detailed description relate to a pseudo-envelope follower power management system for managing the power delivered to a linear RF power amplifier. The pseudo-envelope follower power management system may include a switch mode power supply converter and a parallel amplifier cooperatively coupled to provide a linear RF power amplifier supply to the linear RF power amplifier. The pseudo-envelope follower power management system may include a charge pump configured to power the parallel amplifier. The charge pump may generate a plurality of output voltage levels. The charge pump may be either a boost or a boost/buck charge pump. The pseudo-envelope follower power management system may include an offset voltage control circuit configured to provide feedback to the switch mode power supply converter to regulate an offset voltage developed across a coupling device that couples the output of the parallel amplifier to the linear RF power amplifier supply.

Description

BOOST CHARGE-PUMP WITH FRACTIONAL RATIO AND OFFSET LOOP

FOR SUPPL Y MODULA TION

Related Applications

[0001]This application is a Continuation-in-Part of and claims the benefit of United States Non-Provisional Patent Application Number 13/089,917, filed April 19, 201 1 , entitled "PSEUDO-ENVELOPE FOLLOWING POWER

MANAGEMENT SYSTEM," which claims the benefit of United States Provisional Patent Application Number 61 /325,659, filed April 1 9, 2010, entitled "LTE

PSEUDO-ENVELOPE FOLLOWING SMARTPOWER," both of which are hereby incorporated herein by reference in their entireties.

[0002] Additionally, this application claims the benefit of United States Provisional Application Number 61 /376,877, filed August 25, 2010, entitled "BOOST

CHARGE-PUMP WITH FRACTIONAL RATIO AND OFFSET LOOP FOR

SUPPLY MODULATION," the disclosure of which is hereby incorporated herein by reference in its entirety.

Field of the Disclosure

[0003] The embodiments described herein relate to a power management system for delivering current to a linear RF power amplifier, also referred to as an RF linear power amplifier. More particularly, the embodiments relate to the use of a pseudo-envelope tracker in a power management system of mobile

communications equipment.

Background

[0004] Next-generation mobile devices are morphing from voice-centric

telephones to message and multimedia-based "smart" phones that offer attractive new features. As an example, smart phones offer robust multimedia features such as web-browsing, audio and video playback and streaming, email access and a rich gaming environment. But even as manufacturers race to deliver ever more feature rich mobile devices, the challenge of powering them looms large. [0005] In particular, the impressive growth of high bandwidth applications for radio-frequency (RF) hand-held devices has lead to increased demand for efficient power saving techniques to increase battery life. Because the power amplifier of the mobile device consumes a large percentage of the overall power budget of the mobile device, various power management systems have been proposed to increase the overall power efficiency of the power amplifier.

[0006] As an example, some power managements systems may use a V_RAMP power control voltage to control the voltage presented on a power amplifier collector of a linear RF power amplifier. The linear RF power amplifier may also be referred to as an RF linear power amplifier. As another example, other power management schemes may use a buck converter power supply and a class AB amplifier in tandem to provide power to the linear RF power amplifier.

[0007] Even so, there remains a need to further improve the power efficiency of mobile devices to provide extended battery life. As a result, there is a need to improve the power management system of mobile devices.

Summary

[0008] Embodiments disclosed in the detailed description relate to a pseudo- envelope follower power management system used to manage the power delivered to a linear RF power amplifier. One example embodiment of the pseudo-envelope follower power management system may include a switch mode power supply converter and a parallel amplifier cooperatively coupled to provide a linear RF power amplifier supply to linear RF power amplifier. The pseudo-envelope follower power management system may include a charge pump configured to power the parallel amplifier. The charge pump may generate a plurality of output voltage levels. The charge pump may be either a boost charge pump or a boost/buck charge pump. The pseudo-envelope follower power management system may include an offset voltage control circuit configured to provide feedback to the switch mode power supply converter to regulate an offset voltage developed across a coupling device that couples the output of the parallel amplifier to the linear RF power amplifier supply. [0009] Another example embodiment of a power management system for a linear radio frequency power amplifier includes a switch mode power supply converter and a parallel amplifier operative coupled to generate a linear radio frequency power amplifier supply output for a linear radio frequency power amplifier of a radio frequency device. The switch mode power supply converter may be configured to generate a plurality of switching voltage levels on a switching voltage output. The switching voltage output of the switch mode power supply converter may be coupled via a power inductor to the linear radio frequency power amplifier supply output. A bypass capacitor may be coupled between the linear radio frequency power amplifier supply output and ground such that the power inductor and bypass capacitor form a low pass filter for the switch mode power supply converter. The parallel amplifier may include a parallel amplifier output coupled, via a coupling device, to the linear radio frequency power amplifier supply output. As an example, the coupling device may be a coupling capacitor. The power management system may further include a charge pump configured to provide a charge pump parallel amplifier power supply output. The charge pump may include a first flying capacitor, a second flying capacitor, a plurality of switches operably coupled to form the charge pump parallel amplifier power supply output. The charge pump may be configured to selectively generate a various output voltage levels, derived from a supply voltage, on the charge pump parallel amplifier power supply output. In addition, the charge pump parallel amplifier power supply output may be configured to provide an operational power supply voltage to the parallel amplifier.

[0010]Another example embodiment of a pseudo-envelope follower power management system may include a multi-level charge pump buck converter and a parallel amplifier configured to operate in tandem to generate a power amplifier supply voltage output for a linear RF power amplifier. The multi-level charge pump buck converter may include a supply input configured to receive a direct current (DC) voltage, and a switching voltage output. The switching voltage output is coupled to the power amplifier supply voltage output by a power inductor, where the power inductor couples to a bypass capacitor to form an output filter for the switching voltage output of the multi-level charge pump buck converter. The parallel amplifier may include a supply input configured to receive the direct current (DC) voltage, an amplifier output, a first control input configured to receive a V_RAMP signal, and a second control input configured to receive the power amplifier supply voltage. The amplifier output may be coupled to the power amplifier supply voltage by a coupling circuit. In some embodiments of the pseudo-envelope follower system, the coupling circuit may be an offset capacitor. In other embodiments of the pseudo-envelope follower system, the coupling circuit may be a wire trace such that the offset voltage between the amplifier output and the power amplifier supply voltage is zero volts.

[0011 ] In addition, the multi-level charge pump buck converter may generate a feed forward control signal configured to provide an indication of the output state of the switching voltage output to the parallel amplifier. In some embodiments, the switching voltage output is provided as the feed forward control signal. In other embodiments, the feed forward control signal is generated by a switcher control circuit and provides an indication of the switching voltage output based on the state of the switcher control circuit. The parallel amplifier may include a power amplifier output current estimate signal that provides an estimate of the output current of the parallel amplifier. In some embodiments of the pseudo- envelope follower system, the parallel amplifier may also generate a threshold offset signal. The threshold offset signal may be configured to estimate the magnitude of the offset voltage appearing across the coupling circuit.

[0012]The multi-level buck converter may include a supply input configured to receive a direct current (DC) voltage, a switching voltage output coupled to a power inductor, a switcher control circuit, a multi-level charge pump circuit having a control input, a charge pump supply input configured to receive the DC voltage, a series switch having a first switch terminal, a second switch terminal, and a series control terminal and a shunt switch having a first switch terminal, a second switch terminal, and a shunt control terminal. The first terminal of the series switch may be coupled to the supply input of the multi-level buck converter. The second terminal of the series switch may be coupled to the first terminal of the series switch to form a switching voltage output. The second terminal of the series switch may be coupled to ground. The boost charge pump circuit may include a charge pump control input, a charge pump supply input coupled to the supply input of the multi-level buck converter, and a charge pump output coupled to the supply input of the multi-level buck converter. The boost charge pump includes a plurality of switches and two flying capacitors that provide for three modes of operation. In a charging mode of operation, the flying capacitors are coupled in series between the charge pump supply input and ground, wherein the flying capacitors are switchably disconnected from the charge pump output. In a first boost mode of operation, the flying capacitors are arranged in parallel between the charge pump output and the charge pump supply input to generate a 1 .5 x DC voltage output at the charge pump output. In a second boost mode of operation, the flying capacitors are arranged in series between the charge pump output and the charge pump supply input to generate a 2 x DC voltage output at the charge pump output. The multi-level buck converter may include four mode of operation. In a first mode of operation, the series switch is open, the boost charge pump is in the charging mode of operation, and the shunt switch is closed to generate zero volts at the switching voltage output. In a second mode of operation, the series switch is closed, the boost charge pump is in the charging mode of operation, and the shunt switch is open to generate the DC voltage output at the switching voltage output. In a third mode of operation, both the series switch and the shunt switch are open and the boost charge pump is in the first boost mode of operation to generate a 1 .5 x the DC voltage output at the switching mode output. In a fourth mode of operation, both the series switch and the shunt switch are open and the boost charge pump is in the second boost mode of operation to generate a 2 x the DC voltage output at the switching mode output.

[0013] Those skilled in the art will appreciate the scope of the disclosure and realize additional aspects thereof after reading the follower detailed description in association with the accompanying drawings. Brief Description of the Drawings

[0014] The accompanying drawings incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure.

[0015] Figure 1 A depicts an embodiment of a pseudo-envelope follower power management system for managing power supplied to a linear RF power amplifier.

[0016] Figure 1 B depicts an embodiment of a pseudo-envelope follower power management system for managing power supplied to a linear RF power amplifier.

[0017] Figure 2A depicts an embodiment of the pseudo-envelope follower power management system of Figure 1 A in further detail.

[0018] Figure 2B depicts an embodiment of the pseudo-envelope follower power management system of Figure 1 B in further detail.

[0019] Figure 3A depicts an embodiment of a portion of a multi-level charge pump buck converter.

[0020] Figure 3B depicts another embodiment of a portion of a multi-level charge pump buck converter.

[0021] Figure 3C depicts another embodiment of a portion of a multi-level charge pump buck converter.

[0022] Figure 3D depicts another embodiment of a portion of a multi-level charge pump buck converter.

[0023] Figure 3E depicts another embodiment of a portion of a buck converter.

[0024] Figure 3F depicts another embodiment of a portion of a buck converter.

[0025] Figure 3G depicts another embodiment of a portion of a buck converter.

[0026] Figure 3H depicts another embodiment of a portion of a buck converter.

[0027]

[0028] Figure 4A depicts an embodiment of a threshold detector and control circuit of a switcher control circuit of a multi-level charge pump buck converter. .

[0029] Figure 4B depicts another embodiment of a threshold detector and control circuit of a switcher control circuit of a multi-level charge pump buck converter. [0030] Figure 4C depicts another embodiment of a threshold detector and control circuit of a switcher control circuit of a multi-level charge pump buck converter.

[0031] Figure 4D depicts another embodiment of a threshold detector and control circuit of a switcher control circuit of a multi-level charge pump buck converter.

[0032] Figure 4E depicts an embodiment of a threshold detector and control circuit of a buck converter.

[0033] Figure 4F depicts another embodiment of a threshold detector and control circuit of a buck converter.

[0034] Figure 4G depicts another embodiment of a threshold detector and control circuit of a buck converter.

[0035] Figure 4H depicts another embodiment of a threshold detector and control circuit of a buck converter.

[0036] Figure 5A depicts an embodiment of a first state machine of the threshold detector and control circuit of Figure 4A.

[0037] Figure 5B depicts an embodiment of a first state machine of the threshold detector and control circuit of Figure 4B.

[0038] Figure 5C depicts an embodiment of a first state machine of the threshold detector and control circuit of Figure 4C.

[0039] Figure 5D depicts an embodiment of a first state machine of the threshold detector and control circuit of Figure 4D.

[0040] Figure 5E depicts an embodiment of a first state machine of the threshold detector and control circuit of Figure 4E

[0041] Figure 5F depicts an embodiment of a first state machine of the threshold detector and control circuit of Figure 4F

[0042] Figure 5G depicts an embodiment of a first state machine of the threshold detector and control circuit of Figure 4G

[0043] Figure 5H depicts an embodiment of a first state machine of the threshold detector and control circuit of Figure 4H

[0044] Figure 6A depicts an embodiment of a second state machine of the threshold detector and control circuit of Figure 4A. [0045] Figure 6B depicts an embodiment of a second state machine of the threshold detector and control circuit of Figure 4B.

[0046] Figure 6C depicts an embodiment of a second state machine of the threshold detector and control circuit of Figure 4C.

[0047] Figure 6D depicts an embodiment of a second state machine of the threshold detector and control circuit of Figure 4D.

[0048] Figure 7A depicts one embodiment of a multi-level charge pump circuit of a pseudo-envelope follower power management system.

[0049] Figure 7B depicts another embodiment of a multi-level charge pump circuit of a pseudo-envelope follower power management system.

[0050] Figure 7C depicts still another embodiment of a multi-level charge pump circuit of a pseudo-envelope follower power management system.

[0051 ] Figure 8 depicts one embodiment of a VOFFSET IOOP circuitry of a parallel amplifier circuit of a pseudo-envelope follower power management system.

[0052] Figure 9A depicts an embodiment of the open loop assist circuit of a parallel amplifier circuit of a pseudo-envelope follower power management system.

[0053] Figure 9B depicts an embodiment of the open loop assist circuit of a parallel amplifier circuit of a pseudo-envelope follower power management system.

[0054] Figure 10A depicts an embodiment of a parallel amplifier output

impedance compensation circuit of a parallel amplifier circuit of a pseudo- envelope follower power management system.

[0055] Figure 1 1 A depicts one embodiment of the indication of the switching voltage output generated by a multi-level charge pump buck converter in a pseudo-envelope follower power management system.

[0056] Figure 1 1 B depicts another embodiment of the indication of the switching voltage output generated by a multi-level charge pump buck converter in a pseudo-envelope follower power management system. [0057] Figure 1 1 C depicts another embodiment of the indication of the switching voltage output generated by a multi-level charge pump buck converter in a pseudo-envelope follower power management system.

[0058] Figure 1 1 D depicts another embodiment of the indication of the switching voltage output generated by a multi-level charge pump buck converter in a pseudo-envelope follower power management system.

[0059] Figure 1 1 E depicts another embodiment of the indication of the switching voltage output generated by a multi-level charge pump buck converter in a pseudo-envelope follower power management system.

[0060] Figure 1 1 F depicts another embodiment of the indication of the switching voltage output generated by a multi-level charge pump buck converter in a pseudo-envelope follower power management system

[0061] Figure 12A depicts one embodiment of a parallel amplifier used in a pseudo-envelope follower power management system.

[0062] Figure 12B depicts one embodiment of a rechargeable parallel amplifier used in a pseudo-envelope follower power management system.

[0063] Figure 12C depicts another embodiment of a rechargeable parallel amplifier used in a pseudo-envelope follower power management system.

[0064] Figure 12D depicts one embodiment of a parallel amplifier used in a pseudo-envelope follower power management system.

[0065] Figure 12E depicts another embodiment of a rechargeable parallel amplifier used in a pseudo-envelope follower power management system.

[0066] Figure 12F depicts another embodiment of a rechargeable parallel amplifier used in a pseudo-envelope follower power management system.

[0067] Figure 13 depicts an embodiment of a pseudo-envelope follower power management system including a buck converter and a parallel amplifier circuit having an open loop assist circuit and a parallel amplifier circuit.

[0068] Figure 14 depicts another embodiment of a pseudo-envelope follower power management system including a multi-level charge pump buck converter and a parallel amplifier circuit having an open loop assist circuit and a parallel amplifier circuit. [0069] Figure 15 depicts another embodiment of a pseudo-envelope follower power management system including a multi-level charge pump buck converter and a parallel amplifier circuit having a parallel amplifier circuit and a VOFFSET loop circuit.

[0070] Figure 16 depicts another embodiment of a pseudo-envelope follower power management system including a multi-level charge pump buck converter and a parallel amplifier circuit having a parallel amplifiers VOFFSET loop circuit, an open loop assist circuit and a parallel amplifier output impedance compensation circuit.

[0071 ] Figure 17A depicts another embodiment of pseudo-envelope follower power management system including a buck converter and a parallel amplifier circuit having a rechargeable parallel amplifier circuit.

[0072] Figure 17B depicts another embodiment of a pseudo-envelope follower power management system including a buck converter and a parallel amplifier circuit having a parallel amplifier circuit.

[0073] Figure 18A depicts an embodiment of a pseudo-envelope follower power management system having a multi-level charge pump buck converter and a a μθ charge pump circuit configured to provide a parallel amplifier power supply to a parallel amplifier circuit.

[0074] Figure 18B depicts another embodiment of a pseudo-envelope follower power management system having a multi-level charge pump buck converter and a a μθ charge pump circuit configured to provide a parallel amplifier power supply to a parallel amplifier circuit.

[0075] Figure 18C depicts an embodiment of a pseudo-envelope follower power management system having a buck converter and a μθ charge pump circuit configured to provide a parallel amplifier power supply to a parallel amplifier circuit.

[0076] Figure 18D depicts another embodiment of a pseudo-envelope follower power management system having a buck converter and a μθ charge pump circuit configured to provide a parallel amplifier power supply to a parallel amplifier circuit. [0077] Figure 1 9A depicts an embodiment of a μC charge pump circuit configured to provide a parallel amplifier power supply to a parallel amplifier circuit of a pseudo-envelope follower power management system.

[0078] Figure 1 9B depicts another embodiment of a μC charge pump circuit configured to provide a parallel amplifier power supply to a parallel amplifier circuit of a pseudo-envelope follower power management system, where the μC charge pump circuit includes both buck and boost modes of operation.

[0079] Figures 20A-C depicts functionally equivalent circuit topologies of the μC charge pump circuit of Figure 1 9A for different modes of operation of the μC charge pump circuit.

[0080] Figures 21 depicts a method for configuring a μC charge pump circuit to provide a supply voltage to a parallel amplifier prior to commencement of a data transmission by a linear RF power amplifier.

[0081] Figure 22 depicts a method for pre-charging a VOFFSET Loop Circuit prior to commencement of a data transmission by a linear RF power amplifier.

Detailed Description

[0082] The embodiments set forth below represent the necessary information to enable those skilled in the art to practice the disclosure and illustrate the best mode of practicing the disclosure. Upon reading the following description in light of the accompanying drawings, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims.

[0083] Embodiments disclosed herein relate to a pseudo-envelope follower power management system used to manage the power delivered to a linear RF power amplifier. One example embodiment of the pseudo-envelope follower power management system may include a switch mode power supply converter and a parallel amplifier cooperatively coupled to provide a linear RF power amplifier supply to linear RF power amplifier. The pseudo-envelope follower power management system may include a charge pump configured to power the parallel amplifier. The charge pump may generate a plurality of output voltage levels. The charge pump may be either a boost charge pump or a boost/buck charge pump. The pseudo-envelope follower power management system may include an offset voltage control circuit configured to provide feedback to the switch mode power supply converter to regulate an offset voltage developed across a coupling device that couples the output of the parallel amplifier to the linear RF power amplifier supply.

[0084] Another example embodiment of a power management system for a linear radio frequency power amplifier includes a switch mode power supply converter and a parallel amplifier operative coupled to generate a linear radio frequency power amplifier supply output for a linear radio frequency power amplifier of a radio frequency device. The switch mode power supply converter may be configured to generate a plurality of switching voltage levels on a switching voltage output. The switching voltage output of the switch mode power supply converter may be coupled via a power inductor to the linear radio frequency power amplifier supply output. A bypass capacitor may be coupled between the linear radio frequency power amplifier supply output and ground such that the power inductor and bypass capacitor form a low pass filter for the switch mode power supply converter. The parallel amplifier may include a parallel amplifier output coupled, via a coupling device, to the linear radio frequency power amplifier supply output. As an example, the coupling device may be a coupling capacitor. The power management system may further include a charge pump configured to provide a charge pump parallel amplifier power supply output. The charge pump may include a first flying capacitor, a second flying capacitor, a plurality of switches operably coupled to form the charge pump parallel amplifier power supply output. The charge pump may be configured to selectively generate a various output voltage levels, derived from a supply voltage, on the charge pump parallel amplifier power supply output. In addition, the charge pump parallel amplifier power supply output may be configured to provide an operational power supply voltage to the parallel amplifier.

[0085] Another example embodiment of a pseudo-envelope follower power management system may include a multi-level charge pump buck converter and a parallel amplifier configured to operate in tandem to generate a power amplifier supply voltage output for a linear RF power amplifier. The multi-level charge pump buck converter may include a supply input configured to receive a direct current (DC) voltage, and a switching voltage output. The switching voltage output is coupled to the power amplifier supply voltage output by a power inductor, where the power inductor couples to a bypass capacitor to form an output filter for the switching voltage output of the multi-level charge pump buck converter. The parallel amplifier may include a supply input configured to receive the direct current (DC) voltage, an amplifier output, a first control input configured to receive a V_RAMP signal, and a second control input configured to receive the power amplifier supply voltage. The amplifier output may be coupled to the power amplifier supply voltage by a coupling circuit. In some embodiments of the pseudo-envelope follower system, the coupling circuit may be an offset capacitor. In other embodiments of the pseudo-envelope follower system, the coupling circuit may be a wire trace such that the offset voltage between the amplifier output and the power amplifier supply voltage is zero volts.

[0086] In addition, the multi-level charge pump buck converter may generate a feed forward control signal configured to provide an indication of the output state of the switching voltage output to the parallel amplifier. In some embodiments, the switching voltage output is provided as the feed forward control signal. In other embodiments, the feed forward control signal is generated by a switcher control circuit and provides an indication of the switching voltage output based on the state of the switcher control circuit. The parallel amplifier may include a power amplifier output current estimate signal that provides an estimate of the output current of the parallel amplifier. In some embodiments of the pseudo- envelope follower system, the parallel amplifier may also generate a threshold offset signal. The threshold offset signal may be configured to estimate the magnitude of the offset voltage appearing across the coupling circuit.

[0087] The multi-level buck converter may include a supply input configured to receive a direct current (DC) voltage, a switching voltage output coupled to a power inductor, a switcher control circuit, a multi-level charge pump circuit having a control input, a charge pump supply input configured to receive the DC voltage, a series switch having a first switch terminal, a second switch terminal, and a series control terminal and a shunt switch having a first switch terminal, a second switch terminal, and a shunt control terminal. The first terminal of the series switch may be coupled to the supply input of the multi-level buck converter. The second terminal of the series switch may be coupled to the first terminal of the series switch to form a switching voltage output. The second terminal of the series switch may be coupled to ground. The boost charge pump circuit may include a charge pump control input, a charge pump supply input coupled to the supply input of the multi-level buck converter, and a charge pump output coupled to the supply input of the multi-level buck converter. The boost charge pump includes a plurality of switches and two flying capacitors that provide for three modes of operation. In a charging mode of operation, the flying capacitors are coupled in series between the charge pump supply input and ground, wherein the flying capacitors are switchably disconnected from the charge pump output. In a first boost mode of operation, the flying capacitors are arranged in parallel between the charge pump output and the charge pump supply input to generate a 1 .5 x DC voltage output at the charge pump output. In a second boost mode of operation, the flying capacitors are arranged in series between the charge pump output and the charge pump supply input to generate a 2 x DC voltage output at the charge pump output. The multi-level buck converter may include four mode of operation. In a first mode of operation, the series switch is open, the boost charge pump is in the charging mode of operation, and the shunt switch is closed to generate zero volts at the switching voltage output. In a second mode of operation, the series switch is closed, the boost charge pump is in the charging mode of operation, and the shunt switch is open to generate the DC voltage output at the switching voltage output. In a third mode of operation, both the series switch and the shunt switch are open and the boost charge pump is in the first boost mode of operation to generate a 1 .5 x the DC voltage output at the switching mode output. In a fourth mode of operation, both the series switch and the shunt switch are open and the boost charge pump is in the second boost mode of operation to generate a 2 x the DC voltage output at the switching mode output.

[0088] Figures 1 A and 2A depict an example embodiment of pseudo-envelope follower power management system 1 0A including a multi-level charge pump buck converter 1 2, a parallel amplifier circuit 1 4, a power inductor 1 6, a coupling circuit 1 8, and a bypass capacitor (CBYPASS) 1 9. The multi-level charge pump buck converter 1 2 and the parallel amplifier circuit 1 4 may be configured to operate in tandem to generate a power amplifier supply voltage, V_Cc_, at the power amplifier supply node 28 for a linear RF power amplifier 22. The power amplifier supply node 28 provides an output current, Ιουτ, to the linear RF power amplifier 22. The linear RF power amplifier 22 may include a power amplifier input, PIN, configured to receive a modulated RF signal and a power amplifier output, POUT, coupled to an output load, ZLOAD- AS an example, the output load, ZLOAD, may be an antenna.

[0089] The multi-level charge pump buck converter 1 2 may include a supply input 24 configured to receive a direct current (DC) voltage, V_BAT, from a battery 20 and a switching voltage output 26 configured to provide a switching voltage, V_Sw- The switching voltage output 26 may be coupled to the power amplifier supply node 28 by the power inductor 1 6, where the power inductor 1 6 couples to a bypass capacitor (CBYPASS) 1 9 to form an output filter 29 for the switching voltage output 26 of the multi-level charge pump buck converter 1 2. The power inductor 1 6 provides an inductor current, ISVV OUT, to the power amplifier supply node, 28. The parallel amplifier circuit 1 4 may include a supply input 30 configured to receive the direct current (DC) voltage, V_BAT, from the battery 20, an amplifier output 32A, a first control input 34 configured to receive a V_RAMP signal, and a second control input configured to receive the power amplifier supply voltage, Vcc- The parallel amplifier output, V_PARA_AMP, of the parallel amplifier circuit 1 4 may be coupled to the power amplifier supply voltage V_Cc, by a coupling circuit 1 8. In some example embodiments, as depicted in Figure 2A, the parallel amplifier circuit 1 4 may also include a parallel amplifier impedance compensation circuit 37 configured to receive the V_RAMP signal and provide a compensated VRAMP signal, VRAMP_C-

[0090] Thus, the V_RAMP signal may represent either an analog or digital signal that contains the required supply modulation information for a power amplifier collector of a linear RF power amplifier. Typically, it is a differential analog signal that is used for V_RA p(t) to provide common mode rejection against any noise or spurs that could appear on this signal. The V_RA P signal may be generated by a transceiver or modem used to transmit radio-frequency (RF) signals. The transceiver or a modem may generate the VRAMP signal based upon a known RF modulation Amp(t)*cos(2*pi*fRF*t + Phase(t)). The V_RAMP signal may represent the target voltage to be generated at the power amplifier supply node, 28, of the pseudo-envelope follower power management systeml OA, which provides the power amplifier supply voltage, V_Cc, to the linear RF power amplifier 22. Also the VRAMP signal may be generated from a detector coupled to the RF input power amplifier

[0091 ] The parallel amplifier circuit 14 includes an amplifier output 32A that provides a parallel amplifier output, V_PARA_AMP, to the coupling circuit 1 8. The amplifier output 32A sources a parallel amplifier circuit output current, I PAWA_OUT, to the coupling circuit 18. As depicted in Figure 2A, the parallel amplifier circuit output current, I PAWA_OUT, may be provided by a combination of a parallel amplifier output current, I PARA_AMP, provided by the parallel amplifier 35 and the open loop assist circuit current, I ASSIST_J provided by the open loop assist circuit 39.

[0092] Returning to Figures 1 A and 2A, in some embodiments of the pseudo- envelope follower power management system 10A, the coupling circuit 1 8 may be an offset capacitor, COFFSET- An offset voltage, VOFFSET, may be developed across the coupling circuit 1 8. In other embodiments of the pseudo-envelope follower power management system 1 0A, the coupling circuit may be a wire trace such that the offset voltage, VOFFSET, between the parallel amplifier output, VpARA_AMPj and the power amplifier supply voltage output, V_Cc, is zero volts. In still other embodiments, the coupling circuit may be a transformer. [0093] In addition, as depicted in Figure 1 A, 2A, and 3A, the multi-level charge pump buck converter 12 may generate a feed forward control signal, VSWITCHER, 38 to provide an indication of the output state of the switching voltage output 26 to the parallel amplifier circuit 14. As an example, in Figure 3A, the feed forward signal, VSWITCHER, 38 is provided by a switch 43. The switch 43 may be configured by the V_SWITCHER_CONTROL signal to provide either an indication of the switching voltage output, V_SW_EST, 38B or a scaled version of the switch voltage, VSW_SCALED, as the feed forward signal, VSWITCHER, 38, where the indication of the switching voltage output, V_SW_EST, 38B is based on the state of the switcher control circuit 52. In other embodiments of the pseudo-envelope power management system, as depicted in Figure 1 B and Figure 3B, a scaled version of the switch voltage, V_SW_SCALED, 38A and the indication of the switching voltage output, VSW_EST, 38B are provided to the parallel amplifier circuit 14. As another example, in another embodiment of the pseudo-envelope follower power management system 1 0C, depicted in Figure 2B, only the indication of the switching voltage output, V_SW_EST, 38B is provided as a feed forward signal to the parallel amplifier circuit 14B.

[0094] Returning to Figure 1 A, the parallel amplifier circuit 14 may provide a parallel amplifier circuit output current estimate, I PAWA OUT EST, 40 to the multi- level charge pump buck converter 1 2 as an estimate of the parallel amplifier circuit output current I PAWA_OUT, of the parallel amplifier circuit 14. As depicted in Figures 2A and 2B, in some embodiments of the parallel amplifier circuit 14, the parallel amplifier circuit output current estimate, I PAWA OUT EST, 40 includes a scaled parallel amplifier output current estimate, IPARA_AMP_SENSE, and a scaled open loop assist circuit output current estimate, I ASSIST_SENSE- The scaled parallel amplifier output current estimate, I PARA_AMP_SENSE, is a scaled estimate of the parallel amplifier output current, I PARA_AMP, generated by the parallel amplifier 35 of the parallel amplifier circuit 32. The scaled open loop assist circuit current estimate, IASSIST_SENSE, is a scaled estimate of the open loop assist circuit current, IASSIST, generated by the open loop assist circuit 39. In other embodiments of the parallel amplifier circuit 14, which do not include the open loop assist circuit 39, the parallel amplifier circuit output current estimate, I PAWA_OUT_EST, 40 only includes the scaled parallel amplifier output current estimate, I PARA_AMP_SENSE- [0095] In some embodiments of the pseudo-envelope follower power

management system 1 0A of Figure 2A, the parallel amplifier circuit 14A may also provide a threshold offset current, I THRESHOLD_OFFSET_J 42, generated by the VOFFSET loop circuit 41 , as a feedback signal to the multi-level charge pump buck converter 1 2. An embodiment of the VOFFSET Loop Circuit 41 is depicted in Figure 8. The VOFFSET loop circuit 41 may be configured to provide a threshold offset current, ITHRESHOLD_OFFSET, 42 as an estimate of the magnitude of the offset voltage, VOFFSET, appearing across the coupling circuit 1 8. In those cases where the coupling circuit is a wire trace such that VOFFSET is always zero volts, the parallel amplifier circuit 14 may not provide the threshold offset current,

ITHRESHOLD_OFFSET, 42 to the multi-level charge pump buck converter 12.

[0096] Returning to Figure 1 A, the pseudo-envelope follower power management system 1 0A may further include a control bus 44 coupled to a controller 50. The control bus 44 may be coupled to a control bus interface 46 of the multi-level charge pump buck converter 1 2 and the control bus interface 48 of the parallel amplifier circuit 14. The controller 50 may include various logical blocks, modules, and circuits. The controller 50 may be implemented or performed with a processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices. As an example, a combination of computing devices may include a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. The controller may further include or be embodied in hardware and in computer executable instructions that are stored in memory, and may reside, for example, in Random Access Memory (RAM), flash memory, Read Only Memory (ROM), Electrically Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), registers, hard disk, a removable disk, a CD-ROM, or any other form of computer readable medium known in the art. An exemplary storage medium may be coupled to the processor such that a processor can read information from, and write information to, the storage medium. In the

alternative, the storage medium or a portion of the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC.

[0097] As further depicted in Figure 3A, with continuing reference to Figures 1 A and 2A, the multi-level charge pump buck converter 12 may further include an embodiment of the switcher control circuit 52, switcher control circuit 52A, an embodiment of the frequency lock loop (FLL) circuit 54, a frequency lock loop (FFL) circuit 54A, a multi-level charge pump circuit 56, and the switching circuit 58. The switcher control circuit 52A may be in communication with the frequency lock loop (FFL) circuit 54A. The frequency lock loop (FFL) circuit 54A may be in communication with a clock reference 139. The multi-level charge pump circuit 56 and the switching circuit 58 may be configured to receive the DC voltage, VBAT, from the supply input 24 of the multi-level charge pump buck converter 12.

[0098] The clock reference 139 may provide a clock reference signal 139A to the frequency lock loop (FLL) circuit 54A. In addition, switcher control circuit 52A may provide a logic level indication of the switching voltage output, V_SW_EST_OUT, to the frequency lock loop (FLL) circuit 54A. The logic level indication of the switching voltage output, V_SW_EST_OUT, is discussed relative to the logic circuit 148 of Figure 4A. In some embodiments of the multi-level charge pump buck converter 12, the multi-level charge pump buck converter 12 may not include the frequency lock loop (FLL) circuit 54 and a clock reference 139, as depicted in Figure 3C.

[0099] The switcher control circuit 52A may be configured to receive the parallel amplifier circuit output current estimate, I PAWA_OUT_EST, 40 and the threshold offset signal, ITHRESHOLD_OFFSET, 42 from the parallel amplifier circuit 14. The switcher control circuit 52A may provide a charge pump mode control output signal 60 to the charge pump mode control input 62 of the multi-level charge pump circuit 56. Based upon the charge pump mode control output signal 60, the multi-level charge pump circuit 56 may generate one of a plurality of output voltages or present an open circuit at the charge pump output 64. The switcher control circuit 52A may further provide a series switch control signal 66 and a shunt switch control signal 68 to the switching circuit 58.

[00100] The switching circuit 58 may include a series switch 70 and a shunt switch 72. The series switch 70 and a shunt switch 72 may be a solid state based switch such as a field effect transistor, an insulator-on-semiconductor based transistor, or a bipolar based transistor. The series switch 70 may include a first switch terminal 74, a second switch terminal 76, and a series switch control terminal 78 coupled to the series switch control signal 66. The shunt switch 72 may include a first switch terminal 80, a second switch terminal 82, and a shunt switch control terminal 84 coupled to the shunt switch control signal 68. The first switch terminal 74 of the series switch 70 may be coupled to the supply input 24 of the multi-level charge pump buck converter 12, as depicted in Figures 1 A and 2A. The second switch terminal 76 of the series switch 70 may be coupled to the first switch terminal 80 of the shunt switch 72 and the charge pump output 64 to form the switching voltage output 26. The second switch terminal 82 of the shunt switch 72 may be coupled to ground.

[00101] As depicted in Figure 7A, with continuing reference to Figures 1 A, 2A and 3A, the multi-level charge pump circuit 56 may include charge pump control circuit 84, a plurality of switches 86, 88, 90, 92, 94, 96 and 98, a first flying capacitor 100 having a first terminal 100A and a second terminal 100B, and a second flying capacitor 102 having a first terminal 102A and a second terminal 102B. Each of the plurality of switches 86, 88, 90, 92, 94, 96 and 98 may be a solid state based switch implemented with field effect transistors, insulator-on- semiconductor based transistors, or bipolar based transistors, or a combination thereof. Each of the plurality of switches 86, 88, 90, 92, 94, 96 and 98 may be a solid state transmission gate. As another example, each of the plurality of switches 86, 88, 90, 92, 94, 96 and 98 may be based on a GaN process.

Alternatively, each of the plurality of switches 86, 88, 90, 92, 94, 96 and 98 may be micro-electromechanical systems (MEMS) contact type switches.

[00102] The plurality of switches 86, 88, 90, 92, 94, 96 and 98 may include a first switch 86, a second switch 88, a third switch 90, a fourth switch 92, a fifth switch 94, a sixth switch 96, and a seventh switch 98. The first switch 86 may be coupled between the first terminal 100A of the first flying capacitor 100 and the charge pump output 64. The first switch 86 may include a first switch control input configured to receive a first switch control signal 104 from the charge pump control circuit 84A, where the first switch control signal 104 operably opens and closes the first switch 86 based upon the charge pump mode control signal 60. The second switch 88 may be coupled between the first terminal 100A of the first flying capacitor 100 and the supply input 24 of the multi-level charge pump buck converter 12. The second switch 88 may include a second switch control input configured to receive a second switch control signal 106 from the charge pump control circuit 84A, where the second switch control signal 106 operably opens and closes the second switch 88 based upon the charge pump mode control signal 60. The third switch 90 may be coupled between the second terminal 100B of the first flying capacitor 100 and the supply input 24 of the multi-level charge pump buck converter 12. The third switch 90 may include a third switch control input configured to receive a third switch control signal 108 from the charge pump control circuit 84, where the third switch control signal 108 operably opens and closes the third switch 90 based upon the charge pump mode control signal 60. The fourth switch 92 may be coupled between the second terminal 100B of the first flying capacitor 100 and the first terminal 102A of the second flying capacitor 102. The fourth switch 92 may include a fourth switch control input configured to receive a fourth switch control signal 1 10 from the charge pump control circuit 84, where the fourth switch control signal 1 10 operably opens and closes the fourth switch 92 based upon the charge pump mode control signal 60. The fifth switch 94 may be coupled between the second terminal of the supply input 24 of the multi-level charge pump buck converter 12 and the second terminal 102B of the second flying capacitor 102 The fifth switch 94 may include a fifth switch control input configured to receive a fifth switch control signal 1 12 from the charge pump control circuit 84, where the fifth switch control signal 1 12 operably opens and closes the fifth switch 94 based upon the charge pump mode control signal 60. The sixth switch 96 may be coupled between the second terminal 102B of the second flying capacitor 102 and ground. The sixth switch 96 may include a sixth switch control input configured to receive a sixth switch control signal 1 14 from the charge pump control circuit 84A, where the sixth switch control signal 1 14 operably opens and closes the sixth switch 96 based upon the charge pump mode control signal 60. The seventh switch 98 may be coupled between the first terminal 102A of the second flying capacitor 102 and the charge pump output 64. The seventh switch 98 includes a seventh switch control input configured to receive a seventh switch control signal 1 16 from the charge pump control circuit 84, where the seventh switch control signal 1 16 operably opens and closes the seventh switch 98 based upon the charge pump mode control signal 60.

[00103] Based upon the charge pump mode control signal 60 received at the charge pump control circuit 84, the charge pump control circuit 84A may configure the plurality of switches 86, 88, 90, 92, 94, 96, and 98 to place the first flying capacitor 100 and the second flying capacitor 102 in various arrangements in order to place the multi-level charge pump circuit 56 in various modes of operation. As an example, the multi-level charge pump circuit 56 may have a charging mode to charge the first flying capacitor 100 and the second flying capacitor 102, a first boost mode to provide 1 .5 x V_BAT at the charge pump output 64, and a second boost mode to provide 2 x V_BAT at the charge pump output 64.

[00104] As an example, in response to receipt of the charge pump mode control signal 60 that indicates the multi-level charge pump circuit 56 should be in the charging mode of operation, the charge pump control circuit 84 configures the first flying capacitor 100 and the second flying capacitor 102 to be coupled in series between the supply input 24 of the multi-level charge pump buck converter 12 and ground, where the first flying capacitor and the second flying capacitor may be switchably disconnected from the charge pump output 64. Assuming that the capacitance of the first flying capacitor 100 and the second flying capacitor 102 are equal, the first flying capacitor 100 and the second flying capacitor 102 each charge to a charged voltage of 1 /2 x V_BAT_. The charge pump control circuit 84 configures the first switch 86 to be open, the second switch 88 to be closed, the third switch 90 to be open, the fourth switch 92 to be closed, the fifth switch 94 to be open, the sixth switch 96 to be closed, and the seventh switch 98 to be open.

[00105] In response to receipt of the charge pump mode control signal 60 that indicates the multi-level charge pump circuit 56 should be in the first boost mode of operation, the charge pump control circuit 84 configures the first flying capacitor 100 and the second flying capacitor 102 to be arranged in parallel between the charge pump output 64 and the supply input 24 (V_BAT) to generate 1 .5 x VBAT at the charge pump output. The charge pump control circuit 84A configures the first switch 86 to be closed , the second switch 88 to be open, the third switch 90 to be closed , the fourth switch 92 to be open, the fifth switch 94 to be closed , the sixth switch 96 to be open, and the seventh switch 98 to be closed.

[00106] In response to receipt of the charge pump mode control signal 60 that indicates the multi-level charge pump circuit 56 should be in the second boost mode of operation, the charge pump control circuit 84 configures the first flying capacitor 100 and the second flying capacitor 102 to be arranged in series between the charge pump output 64 and the supply input 24 (V_BAT) to generate 2 x VBAT at the charge pump output 64. The charge pump control circuit 84A configures the first switch 86 to be closed , the second switch 88 to be open, the third switch 90 to be open, the fourth switch 92 to be closed, the fifth switch 94 to be closed, the sixth switch 96 to be open, and the seventh switch 98 to be open.

[00107] Some embodiments of the multi-level charge pump circuit 56 may further include an eighth switch 1 18 coupled between the second terminal 100B of the first flying capacitor 100 and ground in order to provide for a first output mode of operation. The eighth switch 1 18 may include an eighth switch control input configured to receive an eighth switch control signal 120 from the charge pump control circuit 84, where the eighth switch control signal 120 operably opens and closes the eighth switch 1 18 based upon the charge pump mode control signal 60.

[00108] In the first output mode of operation, the multi-level charge pump circuit 56 may provide ½ x V_BAT at the charge pump output 64. In response to receipt of the charge pump mode control signal 60 that indicates the multi-level charge pump circuit 56 should be in the first output mode of operation, the charge pump control circuit 84 configures the first flying capacitor 100 and the second flying capacitor 102 to be coupled in parallel between the charge pump output 64 and ground. The charge pump control circuit 84 configures the first switch 86 to be closed, the second switch 88 to be open, the third switch 90 to be open, the fourth switch 92 to be open, the fifth switch 94 to be open, the sixth switch 96 to be closed, and the seventh switch 98 to be closed and the eighth switch 1 18 to be closed.

[00109] Otherwise, the charge pump control circuit 84 configures the eighth switch 1 18 to be open when the multi-level charge pump circuit 56 is in the charging mode of operation, the first boost mode of operation, or the second boost mode of operation. Returning to Figure 3A, with continuing reference to Figures 1 A and 2A, the switcher control circuit 52A may include a programmable threshold circuit 122 configured to receive a plurality of programmable threshold levels and one embodiment of a threshold detector and control circuit 132A. The programmable threshold levels may be received from a controller 50 via the control bus 44. As an example, in some embodiments, the controller 50 may provide a shunt level threshold parameter, a series level threshold parameter, a first boost level threshold parameter, and a second boost level threshold parameter. In another embodiment, the controller 50 may further provide a first output threshold parameter.

[001 10] As an example, each of the threshold levels may correspond to one of a plurality of output modes of the multi-level charge pump buck converter 12. As an example, the shunt level threshold parameter may correspond to a shunt output mode of operation. In a shunt output mode of operation of the multi-level charge pump buck converter 1 2, the series switch 70 is open (not conducting), the multi-level charge pump circuit 56 is in the charging mode of operation, and the shunt switch 72 is closed (conducting) to generate zero volts at the switching voltage output 26. The shunt output mode of operation provides a conduct path for current to continue flowing through the power inductor 1 6 when the multi-level charge pump circuit 56 is in the charging mode of operation and the series switch 70 is open (not conducting). The series level threshold parameter may

correspond to a shunt output mode of operation of the multi-level charge pump buck converter 1 2. In a series output mode of operation, the series switch 70 is closed (conducting), the multi-level charge pump circuit 56 is in the charging mode of operation, and the shunt switch 72 is open to generate V_BAT at the switching voltage output 26. The first boost level threshold parameter may correspond to a first boost output mode of operation of the multi-level charge pump buck converter 1 2. In the first boost output mode of operation, both the series switch 70 and the shunt switch 72 are open and the multi-level charge pump circuit 56 is in the first boost mode of operation to generate 1 .5 x V_BAT at the switching voltage output 26. The second boost level threshold parameter may correspond to a second boost output mode of operation of the multi-level charge pump buck converter 1 2. In a second boost output mode of operation, both the series switch 70 and the shunt switch 72 are open and the multi-level charge pump circuit 56 is in the second boost mode of operation to generate a 2 x VBAT at the switching voltage output 26.

[00111] Figure 7B depicts an embodiment of a multi-level charge pump 258, depicted in Figures 1 8A and 1 8B, as multi-level charge pump 258A. The mutli-level charge pump 258A is similar to the multi-level charge pump 56 except the multi-level charge pump 258A further includes a ninth switch 1 1 9 configured to provide an internal charge pump node parallel amplifier supply 294 as an additional output. The ninth switch 1 1 9 may be similar to the plurality of switches 86, 88, 90, 92, 94, 96 and 98 of Figure 7A. In addition, the mult-level charge pump 258A is similar to the multi-level charge pump 56 except that the charge pump control circuit 84A is replaced by a charge pump control circuit 84B. Unlike the charge pump control circuit 84A, the charge pump control circuit 84B further includes a ninth switch control 121 configured to control the ninth switch 1 19.

[001 12] The ninth switch 1 19 may include a ninth switch control input configured to receive a ninth switch control signal 121 from the charge pump control circuit 84B, where the ninth switch control signal 121 operably opens and closes the ninth switch 1 19 based upon the charge pump mode control signal 60. The ninth switch may be operably coupled between the first terminal 102A of the second flying capacitor 102 and the internal chare pump node parallel amplifier supply 294.

[001 13] Operationally, the charge pump control circuit 84B functions similar to the operation of the charge pump control circuit 84A. As an example, the multi-level charge pump circuit 258A may have a charging mode to charge the first flying capacitor 100 and the second flying capacitor 102, a first boost mode to provide 1 .5 x V_BAT at the charge pump output 64, and a second boost mode to provide 2 x V_BAT at the charge pump output 64. However, unlike the charge pump control circuit 84A, the charge pump control circuit 84B s configured to operably close the ninth switch 1 19 when the multi-level charge pump 258A is configure to operate in either the first boost mode to provide 1 .5 x V_BAT at the charge pump output 64 or the second boost mode to provide 2 x V_BAT at the charge pump output 64. Thus, when the ninth switch 1 19 is in a closed state during either the first boost mode of operation or the second boost mode of operation, the voltage appearing on the first terminal 102A of the second flying capacitor 102, is substantially equal to 1 .5 x V_BAT- Advantageously, the configuration of the multi-level charge pump circuit 258A provides the same voltage output level to the internal charge pump node parallel amplifier supply 294, which may improve the ripple noise on the power amplifier supply voltage Vcc

[001 14] Figure 7C depicts another embodiment of a multi-level charge pump 258, depicted in Figures 18A and 18B, as multi-level charge pump 258B. The mutli-level charge pump 258B is similar to the multi-level charge pump 258A of Figure 7C except the ninth switch may be operably coupled between the first terminal 100A of the first flying capacitor 100 and the internal chare pump node parallel amplifier supply 294.

[001 15] Operationally, the charge pump control circuit 84C functions similar to the operation of the charge pump control circuit 84B. As an example, like the multi-level charge pump circuit 258A, the multi-level charge pump circuit 258B may have a charging mode to charge the first flying capacitor 100 and the second flying capacitor 102, a first boost mode to provide 1 .5 x V_BAT at the charge pump output 64, and a second boost mode to provide 2 x V_BAT at the charge pump output 64. In addition, like the charge pump control circuit 84B, the charge pump control circuit 84C is configured to operably close the ninth switch 1 19 when the multi-level charge pump 258B is configure to operate in either the first boost mode to provide 1 .5 x V_BAT at the charge pump output 64 or the second boost mode to provide 2 x V_BAT at the charge pump output 64. Thus, when the ninth switch 1 19 is in a closed state during ether the first boost mode of operation or the second boost mode of operation, the voltage appearing on the first terminal 100A of the first flying capacitor 100. Due to the topological location of the first flying capacitor, the voltage output level provided to the internal charge pump node parallel amplifier supply 294 may be 1 .5 x V_BAT when the multi-level charge pump 258B is configured to operate in the first boost mode and 2.0 x V_BAT when the charge pump 258B is configured to operate in the second boost mode. As a result, advantageously, the multi-level charge pump circuit 258B may provide a higher power supply rail for the parallel amplifier 35 of Figures 18A and 18B. In particular, in the case where the parallel amplifier 35 of Figures 18A and 18B is a rechargeable parallel amplifier, similar to the rechargeable parallel amplifiers 35E of Figure 12E and the rechargeable parallel amplifier 35F of Figure 12F, the saved charge voltage, V_AB on the charge conservation capacitor, CAB, may be increased and result in a larger range of operation of the second output stage, as depicted in Figures 12E and 12F.

[001 16] In those embodiments that further provide a first output threshold parameter (not shown), the first output threshold parameter may correspond to a first output mode of operation of the multi-level charge pump buck converter 12. In the first output mode of operation, both the series switch 70 and the shunt switch 72 are open and the multi-level charge pump circuit 56 is in the first output mode of operation to generate a ½ x V_BAT at the switching voltage output 26.

[001 17] Returning to Figure 3A, based upon the shunt level threshold parameter, the series level threshold parameter, the first boost level threshold parameter, and the second boost level threshold parameter, the programmable threshold circuit 122 generates a shunt level threshold 124, a series level threshold 126, a first boost level threshold 128, and a second boost level threshold 130, respectively, which is provided to the threshold detector and control circuit 132A. In those embodiments that provide for a first output threshold parameter and a first output mode of operation of the multi-level charge pump circuit 56, the programmable threshold circuit 122 may further generate a first output threshold (not shown), which is provided to the threshold detector and control circuit 132A.

[00118] The switcher control circuit 52A may also receive a mode switch control signal 131 from the controller 50. The mode switch control signal 131 may configure the threshold detector and control circuit 132A to operate the multi-level charge pump buck converter in different modes of operation. As an example, the mode switch control signal 131 may configure operation of a state machine within the threshold detector and control circuit 132A that governs how the switching voltage output 26 transitions the switching voltage output 26 to provide different output levels. As a first example embodiment of a state machine within the threshold detector and control circuit 132A, the mode switch control signal 131 may configure the multi-level charge pump buck converter 12 to operate in a first mode of operation, depicted in Figure 5A. As another example embodiment of a state machine within the threshold detector and control circuit 132A, the mode switch control signal 131 may configure the multilevel charge pump buck converter 12 to operate in a second mode of operation, depicted in Figure 6A. [001 19] Continuing with Figure 3A, the switcher control circuit 52A may further include a multiplier circuit 134 and a summing circuit 136. The multiplier circuit may be configured to receive the parallel amplifier circuit output current estimate, IPAWA_OUT EST, and a threshold scalar 137A from the threshold detector and control circuit 132A. The threshold scalar 137A may be provided by FLL circuit 54A, which is one embodiment of the frequency lock loop (FLL) circuit 54 depicted in Figure 2A.

[00120] The FLL circuit 54A receives a reference clock 139A from a clock reference 139 and a logic level indication of the switching voltage output,

VSW_EST_OUT- The FLL circuit 54A extracts the operating frequency of the multilevel charge pump buck converter 12 based upon the logic level indication of the switching voltage output, V_SW_EST_OUT- Thereafter, the FLL circuit 54A compares the extracted operating frequency of the multi-level charge pump buck converter 12 to the reference clock 139A to generate the threshold scalar 137A. The magnitude of the threshold scalar 137A may be used to adjust the operating frequency of the multi-level charge pump buck converter 12. In some

embodiments (not shown), the FLL circuit 54A may provide the threshold scalar 137A directly to the multiplier circuit 134.

[00121 ] The multiplier circuit 134 may multiply the parallel amplifier circuit output current estimate, I PAWA_OUT_EST, by the threshold scalar 137A to generate a scaled parallel amplifier output current estimate 138. The scaled parallel amplifier output current estimate 138 is provided to the summing circuit 136. The summing circuit 136 subtracts the threshold offset current, ITHRESHOLD_OFFSET, from the scaled parallel amplifier output current estimate138 to generate a

compensated parallel amplifier circuit output current estimate, I PAWA_COMP- In those embodiments of the parallel amplifier circuit 14 that do not include the VOFFSET loop circuit 41 , the threshold offset current, ITHRESHOLD_OFFSET, and summing circuit 136 are omitted.

[00122] The scaled parallel amplifier output current estimate 138 may be used to control the operating frequency of the multi-level charge pump buck converter 12 by increasing or decreasing the magnitude of the parallel amplifier circuit output current estimate, I PAWA_OUT_EST- AS an example, the FLL circuit 54A may be configured to increase the magnitude of the threshold scalar 1 37A to increase the magnitude of the scaled parallel amplifier output current estimate 1 38. As the magnitude of the scaled parallel amplifier output current estimate 1 38 increases, the operating frequency of the multi-level charge pump buck converter 1 2 will tend to also increase, which will tend to increase the power inductor current, I SW_OUT, delivered by the power inductor 1 6. The FLL circuit 54A may be further be configured to decrease the magnitude of the threshold scalar 1 37A to decrease the magnitude of the scaled parallel amplifier output current estimate 1 38. As the magnitude of the scaled parallel amplifier output current estimate 1 38 decreases, the magnitude of the scaled parallel amplifier output current estimate 1 38, will tend to decrease the operating frequency of the multilevel charge pump buck converter 1 2. As the operating frequency of the multilevel charge pump buck converter 1 2 decreases, the power inductor current, Isw- OUT, is delivered by the power inductor 16. The threshold offset current,

ITHRESHOLD_OFFSET, may be used to control the offset voltage, VOFFSET, which appears across the coupling circuit 1 8 (Figure 2A).

[001 23] Figure 8 depicts the VOFFSET, Loop Circuit 41 that generates the threshold offset current, ITHRESHOLD_OFFSET- Returning to Figure 3A, as the threshold offset current, ITHRESHOLD_OFFSET, increases above zero current, the value magnitude of the compensated parallel amplifier circuit output current estimate, I PAWA_COMP_EST, is reduced, which tends to lower the output frequency of the multi-level charge pump buck converter 12. As the output frequency of the multi-level charge pump buck converter 12 is decreased, the power inductor current, ISW_OUT_, delivered by the power inductor 1 6 will also decrease. As the power inductor current, I SVV OUT_, delivered by the power inductor 1 6 decreases, the offset voltage, VOFFSET, also decreases because the parallel amplifier circuit output current, I PAWA_OUT, tends to become positive to compensate for the reduction of the power inductor current, ISW_OUT■ As the threshold offset current, ITHRESHOLD_OFFSET, decreases below zero current, the value magnitude of the compensated parallel amplifier circuit output current estimate, I PAWA_COMP, is increased, which tends to increase the output frequency of the multi-level charge pump buck converter 12. As the output frequency of the multi-level charge pump buck converter 1 2 is increased, the power inductor current, ISW_OUT, delivered by the power inductor 1 6 increases. As the power inductor current, ISW_OUT,

increases, the offset voltage, VOFFSET, also tends to increase because the parallel amplifier circuit output current, I PAWA_OUT_J tends to become negative to absorb the increase of the power inductor current, ISVV OUT-

[001 24] As depicted in Figure 4A, with continuing reference to Figures 2A and 3A, the threshold detector and control circuit 1 32A includes a first

comparator 140, a second comparator 142, a third comparator 144, a fourth comparator 146, and a logic circuit 148A. The example embodiment of the logic circuit 148A may include a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gates or transistor logic, discrete hardware components, or any combination thereof. Some embodiments of the logic circuit 148A may be implemented in either a digital or analog processor.

[00125] The first comparator 140 includes a positive terminal coupled to the shunt level threshold 124, a negative terminal coupled to the compensated parallel amplifier circuit output current estimate, I PAWA_COMP, and a first

comparator output configured to generate a shunt level indication 1 50A, which is provided to the logic circuit 148A. When the compensated parallel amplifier circuit output current estimate, I PAWA_COMP, is greater than or equal to the shunt level threshold 1 24, the shunt level indication 1 50A is asserted. When the compensated parallel amplifier circuit output current estimate, I PAWA_COMP, is less than the shunt level threshold 1 24, the shunt level indication 1 50A is de-asserted. The second comparator 142 includes a positive terminal coupled to the series level threshold 1 26, a negative terminal coupled to the compensated parallel amplifier circuit output current estimate, I PAWA_COMP, and a second comparator output configured to generate a series level indication 1 52A, which is provided to the logic circuit 148A. When the compensated parallel amplifier circuit output current estimate, I PAWA_COMP, is greater than or equal to the series level threshold 1 26, the series level indication 1 52A is asserted. When the compensated parallel amplifier circuit output current estimate, I PAWA_COMP, is less than the series level threshold 1 26, the series level indication 1 52A is de-asserted. The third comparator 1 44 includes a positive terminal coupled to the first boost level threshold 1 28, a negative terminal coupled to the compensated parallel amplifier circuit output current estimate, IPAWA_COMP, and a third comparator output configured to generate a first boost level indication 1 54A, which is provided to the logic circuit 1 48A. When the compensated parallel amplifier circuit output current estimate, IPAWA_COMP, is greater than the first boost level threshold 1 28, the first boost level indication 1 54A is asserted. When the compensated parallel amplifier circuit output current estimate, IPAWA_COMP, is less than the first boost level threshold 1 28, the first boost level indication 1 54A is de-asserted. The fourth comparator 1 46 includes a positive terminal coupled to the second boost level threshold 1 30, a negative terminal coupled to the compensated parallel amplifier circuit output current estimate, IPAWA_COMP, and a fourth comparator output configured to generate a second boost level indication 1 56A, which is provided to the logic circuit 148A. When the compensated parallel amplifier circuit output current estimate, I PAWA_COMP, is greater than the second boost level threshold 1 30, the second boost level indication 1 56A is asserted. When the compensated parallel amplifier circuit output current estimate, IPAWA_COMP, is less than the second boost level threshold 1 30, the second boost level indication 1 56A is de- asserted.

[00126] The threshold detector and control circuit 1 32A may further include a first output buffer 1 58, a second output buffer 1 60, and a third output buffer 1 61 . The threshold detector and control circuit 1 32A provides a series switch control output 1 62 to the first output buffer 1 58, which provides the series switch control signal 66 to the series switch 70. The threshold detector and control circuit 1 32A provides a shunt switch control output 1 64 to the second output buffer 1 60, which provides the shunt switch control signal 68 to the shunt switch 72. In addition, the threshold and control circuit 1 32A provides one or more switching voltage output cmos signals, V_SW_EST_CMOS_SIGNAL(S), 1 66, to the third output buffer 1 61 , which provide the switching voltage output, V_SW_EST, 38B. Each of the one or more switching voltage output cmos signals,

VSW_EST_CMOS_SIGNAL(S), indicates an output mode of the multi-level charge pump buck converter 12. Based upon one or more switching voltage output cmos signals, V_SW_EST_CMOS_SIGNAL(S), the third output buffer 161 generates the switching voltage output, V_SW_EST, 38B. The third output buffer 161 is supplied by the DC voltage, VBAT, such that the output of the third output buffer 161 does not exceed the DC voltage, V_BAT-

[00127] Figures 1 1 A-F depict various waveforms that may be used to represent the switching voltage output, V_SW_EST, 38B. Figure 1 1 A depicts one embodiment of the switching voltage output, V_SW_EST, 38B. When the multi-level charge pump buck converter 12 is in either the series output mode, the first boost output mode, or the second boost output mode, the third output buffer 161 outputs a boost/series mode level. Alternatively, when multi-level charge pump buck converter 12 is in the shunt output mode, the third output buffer 161 outputs a shunt mode level.

[00128] Figure 1 1 B depicts another embodiment of the switching voltage output, VSW_EST, 38B. When the multi-level charge pump buck converter 12 is in the series output mode, the third output buffer 161 generates a series level.

When the multi-level charge pump buck converter 12 is in either the first boost output mode or the second boost output mode, the third output buffer 161 outputs a boost mode level. Alternatively, when multi-level charge pump buck converter 12 is in the shunt output mode, the third output buffer 161 outputs a shunt mode level.

[00129] Figure 1 1 C depicts another embodiment of the switching voltage output, VSW_EST, 38B. When the multi-level charge pump buck converter 12 is in the series output mode, the third output buffer 161 generates a series level.

When the multi-level charge pump buck converter 12 is in the first boost output mode the third output buffer 161 generates a first boost level. When the multilevel charge pump buck converter 12 is in the second boost output mode, the third output buffer 161 outputs a second boost mode level. Alternatively, when the multi-level charge pump buck converter 1 2 is in the shunt output mode, the third output buffer 1 61 outputs a shunt mode level.

[00130] Figure 1 1 D depicts another embodiment of the switching voltage output, VSW_EST, 38B for the case where the multi-level charge pump circuit 56 includes a first output mode of operation. When the multi-level charge pump buck converter 1 2 is in the first output mode of operation, the third output buffer 1 61 generates a first output level. When the multi-level charge pump buck converter 1 2 is in the series output mode, the third output buffer 1 61 generates a series level. When the multi-level charge pump buck converter 1 2 is in the first boost output mode, the third output buffer 1 61 generates a first boost level.

When the multi-level charge pump buck converter 1 2 is in the second boost output mode, the third output buffer 1 61 outputs a second boost mode level. Alternatively, when multi-level charge pump buck converter 1 2 is in the shunt output mode, the third output buffer 1 61 outputs a shunt level.

[00131] Figure 1 1 E depicts another embodiment of the switching voltage output, VSW_EST, 38B for the case where the multi-level charge pump circuit 56 includes a first output mode of operation. When the multi-level charge pump buck converter 1 2 is in the first output mode of operation, the third output buffer 1 61 generates a first output level. However, when the multi-level charge pump buck converter 1 2 is in either the series output mode, the first boost output mode, or the second boost output mode, the third output buffer 1 61 generates a boost/series level. Alternatively, when the multi-level charge pump buck converter 1 2 is in the shunt output mode, the third output buffer 1 61 outputs a shunt mode level.

[00132] Figure 1 1 F depicts another embodiment of the switching voltage output, VSW_EST, 38B for the case where the multi-level charge pump circuit 56 includes a first output mode of operation. When the multi-level charge pump buck converter 1 2 is in either the series output mode, the first boost mode, or the second boost mode, the third output buffer 1 61 generates a boost/series level. Alternatively, when the multi-level charge pump buck converter 1 2 is in either the first output mode of operation or the shunt output mode, the third output buffer 161 outputs a shunt level.

[00133] Figure 8 depicts the VOFFSET Loop Circuit 41 that generates the threshold offset current, ITHRESHOLD_OFFSET, based upon a calculated value of

VOFFSET and a target offset voltage, VOFFSET TARGET- The target offset voltage, VOFFSET TARGET, may be based upon a parameter provided by the controller 50 to the parallel amplifier circuit 14.

[00134] The VOFFSET Loop Circuit 41 includes a first subtractor circuit, a second subtractor circuit, and an integrator circuit. The first subtractor circuit may be configured to receive the power amplifier supply voltage V_Cc and the parallel amplifier output, V_PARA_AMP- The first subtractor circuit subtracts the parallel amplifier output, V_PARA_AMP from the power amplifier supply voltage V_Cc to generate the offset voltage, VOFFSET, which appears across the coupling circuit 18 (Figure 1 A). The second subtractor circuit receives the offset voltage, VOFFSET, and the target offset voltage, VOFFSET TARGET- The second subtractor circuit subtracts the target offset voltage, V₀FFSET_TARGET, from the offset voltage,

VOFFSET, to generate an offset error voltage, V₀FFSET_ERROR, which is provided to the integrator circuit. The integrator circuit integrates the offset error voltage, VOFFSET_ERROR, to generate the threshold offset current, ITHRESHOLD_OFFSET, which is provided to the multi-level charge pump buck converter 12 (Figure 1 A).

[00135] The operation of the logic circuit 148A of Figure 4A will now be discussed with continuing reference to Figures 2A, 3A, 5A, 6A, and 7. The logic circuit 148A may be digital or analog based logic configured for one or more state machines of the threshold detector and control circuit 132A. As an example embodiment, the logic circuit 148A (Figure 4A) may have a first state machine corresponding to a first mode of operation of the multi-level charge pump buck converter 12, depicted in Figure 5A, and a second state machine corresponding to a second mode of operation of the multi-level charge pump buck converter 12, depicted in Figure 6A. Based on the mode switch control signal 131 received by the threshold detector and control circuit 132A, the threshold detector and control circuit 132A may configure the logic circuit 148A to use the first state machine to govern operation of the multi-level charge pump buck converter 12 using the first state machine of the logic circuit 148A, depicted in Figure 5A. Alternatively, the threshold detector and control circuit 132A may configure the logic circuit 148A to use the second state machine to govern operation of the multi-level charge pump buck converter 12 using the second state machine of the logic circuit 148A, depicted in Figure 6A.

[00136] As depicted in Figure 4A, the logic circuit 148A may include a boost lockout counter 184 and a boost time counter 186. The boost time counter 186 may be used to keep track of the time that the multi-level charge pump buck converter 12 of Figure 2A is in either the first boost output mode or the second output boost mode. When the multi-level charge pump buck converter 12 is in either the first boost output mode or the second boost output mode, the multilevel charge pump circuit 56 (Figure 3A) is configured to be in either the first boost mode of operation or the second boost mode of operation, respectively. In one embodiment of the logic circuit 148A, when the logic circuit 148A determines that the multi-level charge pump buck converter 12 is in either the first boost output mode or the second output boost mode, the logic circuit 148A resets the counter output of the boost time counter 186 and enables the boost time counter 186 to begin counting up. The logic circuit 148A compares the counter output of the boost time counter 186 to a maximum boost time parameter, which may be provided by controller 50. If the counter output of the boost time counter 186 is equal to or exceeds the maximum boost time parameter before the multi-level charge pump buck converter 12 is configured to return to either the shunt output mode of operation or the series output mode of operation, the logic circuit 148A asserts a minimum charge time indicator. However, if the multi-level charge pump buck converter 12 returns to either the series output mode of operation or the shunt output mode of operation while the counter output of the boost time counter 186 is less than the maximum boost time parameter, the logic circuit 148A de-asserts the minimum charge time indicator.

[00137] The boost lockout counter 184 may be a count-down timer that is used to ensure that the multi-level charge pump circuit 56 of Figures 2A and 3A remains in a charging mode of operation for a minimum charge time period after the multi-level charge pump circuit 56 has been in either the first boost mode of operation or the second boost mode of operation. This permits the first flying capacitor 100 and the second flying capacitor 102, of Figure 7A, a sufficient amount of time to charge before the multi-level charge pump circuit 56 transitions again into either the first boost mode of operation or the second boost mode of operation. The minimum charge time period may be a parameter provided by the controller 50 via the control bus 44, as depicted in Figure 1 A. Operationally, after the multi-level charge pump buck converter 12 transitions from either the first boost output mode or the second boost output mode to either the shunt output mode of operation or the series output mode of operation, the logic circuit 148A determines whether the minimum charge time indicator is asserted. If the minimum charge time indicator is asserted, the logic circuit 148A sets the count value of the boost lockout counter 184 to an equal minimum charge time period and enables the boost lockout counter 184 to begin counting down. Once the boost lockout counter 184 counts down to zero, the logic circuit 148A is configured to de-assert the minimum charge time indicator.

[00138] Operation of the first state machine implemented in the logic circuit 148A, which is depicted in Figure 5A, will now be described. The first state machine includes a shunt output mode 188A, a series output mode 190A, a first boost output mode 192A, and a second boost output mode 194A.

[00139] In the shunt output mode 188A, the logic circuit 148A (Figure 4A) configures the series switch control output 162 such that the series switch 70 (Figure 3A) is in an open state (not conducting). The logic circuit 148A also configures the shunt switch control output 164 such that the shunt switch 72 is in a closed state (conducting). In addition, the logic circuit 148A configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 (Figure 2A) to be in a charging mode of operation. As a result, the switching voltage output 26 of Figure 3A is configured to provide a switching voltage, V_Sw, substantially equal to ground. In response to assertion of the series level indication 152A, which indicates that the compensated parallel amplifier circuit output current estimate, IPAWA_COMP, is greater than or equal to the series level threshold 126, the logic circuit 148A configures the first state machine to transition to the series output mode 190A. Otherwise the state machine remains in the shunt output mode 188A.

[00140] In the series output mode 190A, the logic circuit 148A configures the series switch control output 162 such that the shunt switch 70 is in a closed state (conducting). The logic circuit 148A also configures the shunt switch control output 164 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 148A configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 to be in a charging mode of operation. As a result, switching voltage output 26 of Figure 3A is configured to provide a switching voltage, V_Sw, substantially equal to the direct current (DC) voltage, V_BAT-

[00141 ] In response to de-assertion of the shunt level indication 150A (Figure 4A), which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_COMP, is less than the shunt level threshold 124, the logic circuit 148A configures the first state machine to transition to the shunt output mode 188A (Figure 5A). However, in response to assertion of the first boost level indication 154A, which indicates that the compensated parallel amplifier circuit output current estimate, IPAWA_COMP, is greater than or equal to the first boost level threshold 128, the logic circuit 148A configures the first state machine to transition to the first boost output mode 192A. Otherwise, the first state machine remains in the series output mode 190A.

[00142] In the first boost output mode 192A, the logic circuit 148A (Figure 4A) configures the series switch control output 162 such that the series switch 70 (Figure 3A) is in an open state (not conducting). The logic circuit 148A also configures the shunt switch control output 164 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 148A configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 to be in a first boost mode of operation to provide 1 .5 x V_BAT at the charge pump output 64. As a result, switching voltage output 26 of Figure 3A is configured to provide a switching voltage, V_Sw, substantially equal to 1 .5 x V_BAT- In response to de-assertion of the shunt level indication 1 50A (Figure 4A), which indicates that the compensated parallel amplifier circuit output current estimate, l pAWA_coMP, is less than the shunt level threshold 1 24, the logic circuit 148A configures the first state machine to transition to the shunt output mode 1 88A (Figure 5A). However, in response to assertion of the second boost level indication 1 56A, which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_COMP, is greater than or equal to the second boost level threshold 1 30, the logic circuit 148A configures the first state machine to transition to the second boost output mode 194A. Otherwise, the first state machine remains in the first boost output mode 1 92A.

[00143] In the second boost output mode 1 94A, the logic circuit 148A (Figure 4A) configures the series switch control output 1 62 such that the series switch 70 (Figure 3A) is in an open state (not conducting). The logic circuit 148A also configures the shunt switch control output 164 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 148A configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 to be in a second boost mode of operation to provide 2 x V_BAT at the charge pump output 64. As a result, the switching voltage output 26 of Figure 3A is configured to provide a switching voltage, V_Sw, substantially equal to 2 x V_BAT- In response to de-assertion of the shunt level indication 1 50A, which indicates that the compensated parallel amplifier circuit output current estimate, l pAWA_coMP, is less than the shunt level threshold 1 24, the first state machine transitions to the shunt output mode 1 88A. Otherwise, the state machine remains in the second boost output mode 1 94A.

[00144] Operation of the second state machine of the logic circuit 148A, which is depicted in Figure 6A, will now be described. The second state machine includes a shunt output mode 1 96A, a series output mode 1 98A, a first boost output mode 200A, and a second boost output mode 202A. In addition, the second state machine uses the above described boost lockout counter 184 and boost time counter 1 86 of the logic circuit 148A. [00145] In the shunt output mode 1 96A, the logic circuit 148A (Figure 4A) configures the series switch control output 1 62 such that the series switch 70 is in an open state (not conducting). The logic circuit 148A also configures the shunt switch control output 1 64 such that the shunt switch 72 is in a closed state (conducting). In addition, the logic circuit 148A configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 (Figure 3A) to be in a charging mode of operation. As a result, switching voltage output 26 of Figure 3A is configured to provide a switching voltage, V_Sw, substantially equal to ground. If the boost lockout counter 1 84 is enabled, the boost lockout counter 1 84 continues to count down. In response to assertion of the

seriesshunt level indication 1 52A, which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_COMP, is greater than or equal to the series level threshold 126, the second state machine transitions to the series output mode 1 98A. Otherwise the second state machine remains in the shunt output mode 1 96A.

[00146] In the series output mode 1 98A, the logic circuit 1 48A (Figure 4A) configures the series switch control output 1 62 such that the series switch 70 is in a closed state (conducting). The logic circuit 148A also configures the shunt switch control output 164 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 148A configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 to be in a charging mode of operation. As a result, switching voltage output 26 of Figure 3A is configured to provide a switching voltage, V_Sw, substantially equal to the direct current (DC) voltage, V_BAT- If the boost lockout counter 1 84 is enabled, the boost lockout counter 1 84 continues to count down. In response to de-assertion of the shunt level indication 1 50A, which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_COMP, is less than the shunt level threshold 124, the logic circuit 148A configures the second state machine to transition to the shunt output mode 1 96A. However, in response to assertion of the first boost level indication 1 54D, which indicates that the compensated power amplifier circuit output current estimate, I PAWA_COMP, is greater than or equal to the first boost level threshold 128, the logic circuit 148A determines whether both the minimum charge time indicator is de-asserted and the first boost level indication is asserted. If the minimum charge time indicator is de-asserted and the first boost level indication is asserted, the logic circuit 148A configures the second machine to transition to the first boost output mode 200A. Otherwise, the logic circuit 148A prevents the second state machine from transitioning to the first boost output mode 200A until the minimum time indicator is de-asserted. Once both the minimum charge time indicator are de-asserted and the first boost level indication 154A is asserted, the logic circuit 148A configures the second state machine to transition to the first boost output mode 200A, resets the counter output of the boost time counter 186, and enables the boost time counter 186 to begin counting up. Otherwise, the second state machine remains in the shunt output mode 198A.

[00147] In the first boost output mode 200A, the logic circuit 148A

configures the series switch control output 162 such that the series switch 70 is in an open state (not conducting). The logic circuit 148A also configures the shunt switch control output 164 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 148A configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 to be in a first boost mode of operation 200A to provide 1 .5 x V_BAT at the charge pump output 64. As a result, the switching voltage output 26 of Figure 3A is configured to provide a switching voltage, V_Sw, substantially equal to 1 .5 x V_BAT- In response to de-assertion of the first boost level indication 154A, which indicates that the compensated parallel amplifier circuit output current estimate,

IPAWA_COMP, is less than the first boost level threshold 128, the logic circuit 148A configures the second state machine to transition to the shunt output mode 198A. If the count output of the boost time counter 186 exceeds the maximum boost time parameter, the logic circuit 148A asserts a minimum charge time indicator. In response to the minimum charge time indicator being asserted, the logic circuit 148A sets the count value of the boost lockout counter 184 and enables the boost lockout counter 184 to begin counting down. However, in response to assertion of the second boost level indication 156A, which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_COMP, is greater than or equal to the second boost level threshold 130, the logic circuit 148A configures the second state machine to transition to the second boost output mode 202A. Otherwise, the second state machine remains in the first boost output mode 200A.

[00148] In the second boost output mode 202A, the logic circuit 148A configures the series switch control output 162 such that the series switch 70 is in an open state (not conducting). The logic circuit 148A also configures the shunt switch control output 164 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 148A configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 (Figure 3a) to be in a second boost mode of operation 200A to provide 2 x V_BAT at the charge pump output 64. As a result, switching voltage output 26 of Figure 3A is configured to provide a switching voltage, V_Sw, substantially equal to 2 x V_BAT- [00149] In response to de-assertion of the first boost level indication 154A, which indicates that the compensated power amplifier circuit output current estimate, IPAWA_COMP, is less than the first boost level threshold 128, the logic circuit 148A configures the second state machine to transition to the series output mode 198A. If the count output of the boost time counter 186 exceeds the maximum boost time parameter, the logic circuit 148A asserts a minimum charge time indicator. In response to the minimum charge time indicator being asserted, the logic circuit 148A sets the count value of the boost lockout counter 184 and enables the boost lockout counter 184 to begin counting down. Otherwise, the second state machine remains in the second boost output mode 202A.

The threshold and control circuit 132A further provides a logic level indication of the switching voltage output , V_SW_EST_OUT, which is a logic level representation of the switching voltage output , V_Sw. The switching voltage output , V_SW_EST_OUT, may be based upon the V_SW_EST_CMOS_SIGNAL(S). In some embodiment of threshold and control circuit 132A, the a logic level indication of the switching voltage output , V_SW_EST_OUT, may be asserted when multi-level charge pump buck converter 12 is in either the series output mode, the first boost output mode, or the second boost output mode. The logic level indication of the switching voltage output , V_SW_EST_OUT, is de-asserted when the multi-level charge pump buck converter 12 is in the shunt output mode.

[00150] Figure 3B depicts another embodiment of switcher control circuit 52, switcher control circuit 52B, and another embodiment of the FLL circuit 54 of the multi-level charge pump buck converter 12, FLL circuit 54B. The operation of the switcher control circuit 52B and the FLL circuit 54B will now be described.

[00151 ] Unlike the FLL circuit 54A depicted in Figure 3B, the FLL circuit 54B outputs a threshold scalar' 137B, Similar to the FLL circuit 54A, the FLL circuit 54B receives a reference clock 139A from a clock reference 139 and a logic level indication of the switching voltage output, V_Sw_ EST OUT- The FLL circuit 54B extracts the operating frequency of the multi-level charge pump buck converter 12 based upon the logic level indication of the switching voltage output, VSW_EST_OUT- Thereafter, the FLL circuit 54B compares the extracted operating frequency of the multi-level charge pump buck converter 12 to the reference clock 139A to generate the threshold scalar' 137B. The magnitude of the threshold scalar' 137B may be used to adjust the operating frequency of the multi-level charge pump buck converter 12. As will be discuss relative to the threshold detector and control circuit 132B of Figure 4B, the FLL circuit 54B provide the threshold scalar' 137B directly to a plurality of multiplier circuits 168, 170, 172, and 174. The plurality of multiplier circuits 168, 170, 172, and 174 may be used to to scale the shunt level threshold 124, the series level threshold 126, the first boost level threshold 128, and the second boost level threshold 130, respectively to generate a scaled shunt level threshold 176, a scaled series level threshold 178, a scaled first boost level threshold 180, and a scaled second boost level threshold 180. The scaled shunt level threshold 176, the scaled series level threshold 178, the scaled first boost level threshold 180, and the scaled second boost level threshold 180 may be used to control the operating frequency of the multi-level charge pump buck converter 12. [00152] As an example, the FLL circuit 54B may be configured to decrease the magnitude of the threshold scalar' 137B to decrease the magnitude of the scaled shunt level threshold 176, the scaled series level threshold 178, the scaled first boost level threshold 180, and the scaled second boost level threshold 180. As the magnitudes of the scaled shunt level threshold 176, the scaled series level threshold 178, the scaled first boost level threshold 180, and the scaled second boost level threshold 180 decrease, the operating frequency of the multi-level charge pump buck converter 12 will tend to increase, which will tend to increase the power inductor current, ISVV OUT, delivered by the power inductor 16.

[00153] The FLL circuit 54B may be configured to increase the magnitude of the threshold scalar' 137B to increase the magnitude of the scaled shunt level threshold 176, the scaled series level threshold 178, the scaled first boost level threshold 180, and the scaled second boost level threshold 180. As the scaled shunt level threshold 176, the scaled series level threshold 178, the scaled first boost level threshold 180, and the scaled second boost level threshold 180 are increased, the operating frequency of the multi-level charge pump buck converter 12 will tend to decrease, which will tend to decrease the power inductor current, ISW_OUT, delivered by the power inductor 16.

[00154] Returning to Figure 3B, unlike the switcher control circuit 52A of Figure 3A, switcher control circuit 52B includes a threshold detector and control circuit 132B. The switcher control circuit 52B omits the multiplier circuit 134. As will be discussed below relative to the threshold detector and control circuit 132B of Figure 4b, the summing circuit 136, is placed in threshold detector and control circuit 132B.

[00155] Also, similar to the switcher control circuit 52A, the switcher control circuit 52B may also receive a mode switch control signal 131 from the controller 50. The mode switch control signal 131 may configure the threshold detector and control circuit 132B to operate the multi-level charge pump buck converter in different modes of operation. As an example, the mode switch control signal 131 may configure operation of a state machine within the threshold detector and control circuit 132B that governs how the switching voltage output 26 transitions the switching voltage output 26 to provide different output levels. As a first example embodiment of a state machine within the threshold detector and control circuit 132B, the mode switch control signal 131 may configure the multi- level charge pump buck converter 12 to operate in a first mode of operation, depicted in Figure 5B. As another example embodiment a state machine within the threshold detector and control circuit 132A, the mode switch control signal 131 may configure the multi-level charge pump buck converter 12 to operate in a second mode of operation, depicted in Figure 6B.

[00156] Referring to Figure 4B, the FLL circuit 54B will now be discussed. Similar to FLL Circuit 54B, the FLL circuit 54B may be configured to receive a clock reference signal 139A from the clock reference circuit 139 and a logic level indication of the switching voltage output , V_SW_EST_OUT, from the switcher control circuit 52B. The logic level indication of the switching voltage output ,

VSW_EST_OUT, may be provided by the logic circuit 148B of the threshold detector and control circuit 132B. As discussed above, the logic level indication of the switching voltage output, V_SW_EST_OUT, is a logic level representation of the switching voltage output, V_Sw.

[00157] The one embodiment of the threshold detector and control circuit 132B includes a first multiplier circuit 168, a second multiplier circuit 170, a third multiplier circuit 172, and a forth multiplier circuit 174. The first multiplier circuit 168 may be configured to receive the shunt level threshold 124 and the receive threshold scalar' 137B. The first multiplier circuit 168 multiplies the shunt level threshold 124 by the receive threshold scalar' 137B to generate a scaled shunt level threshold 176. The second multiplier circuit 170 may be configured to the series level threshold 126 and the threshold scalar' 137B. The second multiplier circuit 170 multiplies the series level threshold 1 26 by the threshold scalar' 137B to generate a scaled series level threshold 178. The third multiplier circuit 172 may be configured to the first boost level threshold 128 and the threshold scalar' 137B. The third multiplier circuit 172 may multiplies the first boost level threshold 128 by the threshold scalar' 137B to generate a scaled first boost level threshold 1 80. The forth multiplier circuit 1 74 may be configured to the second boost level threshold 1 30 and the threshold scalar' 1 37B. The forth multiplier circuit 1 74 multiplies the second boost level threshold 1 30 by the threshold scalar' 1 37B to generate the scaled second boost level threshold 1 82. The summing circuit 1 36 subtract the threshold offset current, ITHRESHOLD_OFFSET, 42 from the parallel amplifier circuit output current estimate, I PAWA_OUT_EST_J 40 to generate a compensated parallel amplifier circuit output current estimate, I PAWA_COMP'- AS discussed before, the threshold offset current, ITHRESHOLD_OFFSET, may be used to control the offset voltage, VOFFSET, that is generated across the coupling circuit 1 8, as depicted in Figure 2A. In the case where the coupling circuit 1 8 is a wire, such that the parallel amplifier output 32A is directly coupled to the power amplifier supply node 28, the VOFFSET loop circuit 41 and the threshold offset current, ITHRESHOLD OFFSET, are omitted such that I PAWA COMP' is the same as parallel amplifier circuit output current estimate, IPAWA_OUT_EST, 40.

[00158] The first comparator 1 40 includes a positive terminal coupled to the scaled shunt level threshold 1 76, a negative terminal coupled to the

compensated parallel amplifier circuit output current estimate, I PAWA COMP'_J and a first comparator output configured to generate a shunt level indication 1 50B, which is provided to the logic circuit 1 48B. When the compensated parallel amplifier circuit output current estimate, I PAWA_COMP' , is greater than or equal to the scaled shunt level threshold 1 76, the shunt level indication 1 50C is asserted. When the compensated parallel amplifier circuit output current estimate, l pAWA_coMp', is less than the scaled shunt level threshold 1 76, the shunt level indication 1 50B is de-asserted. The second comparator 1 42 includes a positive terminal coupled to the scaled series level threshold 1 78, a negative terminal coupled to the compensated parallel amplifier circuit output current estimate, l pAWA_coMp', and a second comparator output configured to generate a series level indication 1 52B, which is provided to the logic circuit 1 48B. When the compensated parallel amplifier circuit output current estimate, I PAWA_COMP', is greater than or equal to the scaled series level threshold 1 78, the series level indication 1 52B is asserted. When the compensated parallel amplifier circuit output current estimate, I PAWA_COMP', is less than the shunt series level threshold 1 78, the series level indication 1 50B is de-asserted. The third comparator 144 includes a positive terminal coupled to the scaled first boost level threshold 1 80, a negative terminal coupled to the compensated parallel amplifier circuit output current estimate, I PAWA_COMP', and a third comparator output configured to generate a first boost level indication 1 54B, which is provided to the logic circuit 148B. When the compensated parallel amplifier circuit output current estimate, l pAWA_coMp', is greater than the scaled first boost level threshold 1 80, the first boost level indication 1 54B is asserted. When the compensated parallel amplifier circuit output current estimate, I PAWA_COMP', is less than the scaled first boost level threshold 180, the first boost level indication 154B is de-asserted. The fourth comparator 146 includes a positive terminal coupled to the scaled second boost level threshold 1 82, a negative terminal coupled to the compensated parallel amplifier circuit output current estimate, I PAWA_COMP ', and a fourth comparator output configured to generate a second boost level indication 1 56B, which is provided to the logic circuit 148B. When the compensated parallel amplifier circuit output current estimate, I PAWA_COMP', is greater than the scaled second boost level threshold 182, the second boost level indication 1 56B is asserted. When the compensated parallel amplifier circuit output current estimate, l pAWA_coMp', is less than the scaled second boost level threshold 1 86, the second boost level indication 1 56B is de-asserted.

[00159] The logic circuit 148B will now be discussed. The logic circuit 148B is similar to the logic circuit 148A of Figure 4A. The example embodiment of the logic circuit 148B may include a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gates or transistor logic, discrete hardware components, or any combination thereof designed to perform. Some

embodiments of the logic circuit 148B may be implemented in either a digital or analog processor. The logic circuit 148B generates the series switch control output 1 62, the shunt switch control output 1 64, the one or more switching voltage output cmos signals, V_Sw_ _EST_CMOS_SIGNAL(S), 1 66, the charge pump control signal 60, and the logic level indication of the switching voltage output , VSW_EST_OUT in a similar fashion as the logic circuit 148A, which has been previously discussed.

[00160] The operation of the logic circuit 148B will now be discussed with continuing reference to Figures 3B, 4B, 5B, 6B, and 7A. Similar to the logic circuit 148A of Figure 4A, the logic circuit 148B may be digital or analog based logic configured for one or more state machines of the threshold detector and control circuit 132B. As an example embodiment, the logic circuit 148B (Figure 4B) may have a first state machine corresponding to a first mode of operation, depicted in Figure 5B and a second state machine corresponding to a second mode of operation, depicted in Figure 6B. Based on the mode switch control signal 131 received by the threshold detector and control circuit 132B, the threshold detector and control circuit 132B may configure the logic circuit 148B to use the first state machine to govern operation of the multi-level charge pump buck converter using the first state machine of the logic circuit 148B, depicted in Figure 5B. Alternatively, the threshold detector and control circuit 132B may configure the logic circuit 148B to use the second state machine to govern operation of the multi-level charge pump buck converter using the second state machine of the logic circuit 148B, depicted in Figure 6B

[00161 ] Also similar to the logic circuit 148A, the logic circuit 148B may include a boost lockout counter 184 and a boost time counter 186. The boost time counter 186 may be used to keep track of the time that the multi-level charge pump buck converter 12 of Figure 2A is in either the first boost output mode or the second output boost mode. When the multi-level charge pump buck converter 12 is in either the first boost output mode or the second boost output mode, the multi-level charge pump circuit 56 (Figure 3B) is configured to be in either the first boost mode of operation or the second boost mode of operation, respectively. In one embodiment of the logic circuit 148B, when the logic circuit 148B determines that the multi-level charge pump buck converter 12 is in either the first boost output mode or the second output boost mode, the logic circuit 148B resets the counter output of the boost time counter 186 and enables the boost time counter 186 to begin counting up. The logic circuit 148B compares the counter output of the boost timer counter 186 to a maximum boost time parameter, which may be provided by controller 50. If the counter output of the boost time counter 186 is equal to or exceeds the maximum boost time parameter before the multi-level charge pump buck converter 12 is configured to return to either the shunt output mode of operation or the series output mode of operation, the logic circuit 148B asserts a minimum charge time indicator.

However, if the multi-level charge pump buck converter 12 returns to either the series output mode of operation or the shunt output mode of operation while the counter output of the boost time counter 186 is less than the maximum boost time parameter, the logic circuit 148B de-asserts the minimum charge time indicator.

[00162] Similar to the boost lockout counter 184 of the logic circuit 148A, The boost lockout counter 184 of the logic circuit 148B may be a count-down timer that is used to ensure that the multi-level charge pump circuit 56 of 3B remains in a charging mode of operation for a minimum charge time period after the multi-level charge pump circuit 56 has been in either the first boost mode of operation or the second boost mode of operation. This permits the first flying capacitor 100 and the second flying capacitor 102 of Figure 7 A a sufficient amount of time to charge before the multi-level charge pump circuit 56 transitions again into either the first boost mode of operation or the second boost mode of operation. Similar to the logic circuit 148A, the minimum charge time period may be a parameter provided by the controller 50 via the control bus 44 to the logic circuit 148B. Operationally, after the multi-level charge pump buck converter 12 transitions from either the first boost output mode or the second boost output mode to either the shunt output mode of operation or the series output mode of operation, the logic circuit 148B determines whether the minimum charge time indicator is asserted. If the minimum charge time indicator is asserted, the logic circuit 148B sets the count value of the boost lockout counter 184 to equal minimum charge time period and enables the boost lockout counter 184 to begin counting down. Once the boost lockout counter 184 counts down to zero, the logic circuit 148B is configured to de-assert the minimum charge time indicator. [00163] Operation of the first state machine implemented in the logic circuit 148B, which depicted in Figure 5B, will now be described. The first state machine includes a shunt output mode 188B, a series output mode 190B, a first boost output mode 192B, and a second boost output mode 194B.

[00164] In the shunt output mode 188B, the logic circuit 148B (Figure 4B) configures the series switch control output 162 such that the series switch 70 (Figure 3B) is in an open state (not conducting). The logic circuit 148B also configures the shunt switch control output 164 such that the shunt switch 72 is in a closed state (conducting). In addition, the logic circuit 148B configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 (Figure 3B) to be in a charging mode of operation. As a result, switching voltage output 26 of Figure 3B is configured to provide a switching voltage, V_Sw, substantially equal to ground. In response to assertion of the shunt level indication 150B, which indicates that the compensated parallel amplifier circuit output current estimate, IPAWA_COMP', is greater than or equal to the scaled series level threshold 178, the logic circuit 148B configures the first state machine to transition to the series output mode 190B. Otherwise the first state machine remains in the shunt output mode 188B.

[00165] In the series output mode 190B, the logic circuit 148B configures the series switch control output 162 such that the shunt switch 70 is in a closed state (conducting). The logic circuit 148B also configures the shunt switch control output 164 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 148B configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 to be in a charging mode of operation. As a result, switching voltage output 26 of Figure 3B is configured to provide a switching voltage, V_Sw, substantially equal to the direct current (DC) voltage, V_BAT-

[00166] In response to de-assertion of the shunt level indication 150B (Figure 4B), which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_COMP', is less than the scaled shunt level threshold 176, the logic circuit 148B configures the first state machine to transition to the shunt output mode 1 88B (Figure 5B). However, in response to assertion of the first boost level indication 1 54B which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_COMP', is greater than or equal to the scaled first boost level threshold 1 80, the logic circuit 1 48B configures the first state machine to transition to the first boost output mode 1 92B. Otherwise, the first state machine remains in the series output mode 1 90B.

[00167] In the first boost output mode 1 92B, the logic circuit 1 48B (Figure 4B) configures the series switch control output 1 62 such that the series switch 70 (Figure 3B) is in an open state (not conducting). The logic circuit 1 48B also configures the shunt switch control output 1 64 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 1 48B configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 to be in a first boost mode of operation to provide 1 .5 x V_BAT at the charge pump output 64. As a result, switching voltage output 26 of Figure 3B is configured to provide a switching voltage, V_Sw, substantially equal to 1 .5 x V_BAT- In response to de-assertion of the shunt level indication 1 50B (Figure 4B), which indicates that the compensated parallel amplifier circuit output current estimate, l pAWA_coMp', is less than the scaled shunt level threshold 1 76, the logic circuit 1 48B configures the first state machine to transition to the shunt output mode 1 88B (Figure 5B). However, in response to assertion of the second boost level indication 1 56B, which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_COMP', is greater than or equal to the scaled second boost level threshold 1 82, the logic circuit 1 48B configures the first state machine to transition to the second boost output mode 1 94B. Otherwise, the first state machine remains in the first boost output mode 1 92B.

[00168] In the second boost output mode 1 94B, the logic circuit 1 48B (Figure 4B) configures the series switch control output 1 62 such that the series switch 70 (Figure 3B) is in an open state (not conducting). The logic circuit 1 48B also configures the shunt switch control output 1 64 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 1 48B configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 to be in a second boost mode of operation to provide 2 x V_BAT at the charge pump output 64. As a result, the switching voltage output 26 of Figure 3B is configured to provide a switching voltage, V_Sw, substantially equal to 2 x V_BAT- In response to de-assertion of the shunt level indication 150B, which indicates that the compensated parallel amplifier circuit output current estimate,

l pAWA_coMp', is less than the scaled shunt level threshold 176, the first state machine transitions to the shunt output mode 188B. Otherwise, the first state machine remains in the second boost output mode 194B.

[00169] Operation of the second state machine of the logic circuit 148B (Figure 3B), which is depicted in Figure 6B, will now be described. The second state machine includes a shunt output mode 196B, a series output mode 198B, a first boost output mode 200B, and a second boost output mode 202B. In addition, the second state machine uses the above described boost lockout counter 184 and boost time counter 186 of the logic circuit 148B.

[00170] In the shunt output mode 196B, the logic circuit 148B (Figure 4B) configures the series switch control output 162 such that the series switch 70 is in an open state (not conducting). The logic circuit 148B also configures the shunt switch control output 164 such that the shunt switch 72 is in a closed state (conducting). In addition, the logic circuit 148B configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 (Figure 2A) to be in a charging mode of operation. As a result, switching voltage output 26 of Figure 3B is configured to provide a switching voltage, V_Sw, substantially equal to ground. If the boost lockout counter 184 is enabled, the boost lockout counter 184 continues to count down. In response to assertion of the shunt level indication 150B, which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_COMP', is greater than or equal to the scaled series level threshold 150, the second state machine transitions to the series output mode 198B. Otherwise the second state machine remains in the shunt output mode 196B.

[00171 ] In the series output mode 198B, the logic circuit 148B (Figure 4B) configures the series switch control output 162 such that the series switch 70 is in a closed state (conducting). The logic circuit 148B also configures the shunt switch control output 164 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 148B configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 to be in a charging mode of operation. As a result, switching voltage output 26 of Figure 3B is configured to provide a switching voltage, V_Sw, substantially equal to the direct current (DC) voltage, V_BAT- If the boost lockout counter 184 is enabled, the boost lockout counter 184 continues to count down. In response to de-assertion of the shunt level indication 150B, which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_COMP', is less than the scaled shunt level threshold 150, the logic circuit 148B configures the second state machine to transition to the shunt output mode 196B. However, in response to assertion of the first boost level indication 154B which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_COMP_J' is greater than or equal to the scaled first boost level threshold 180, the logic circuit 148B determines whether both the minimum charge time indicator is de-asserted and the first boost level indication is asserted. If the minimum charge time indicator is de- asserted and the first boost level indication is asserted, the logic circuit 148B configures the second machine to transition to the first boost output mode 200B. Otherwise, the logic circuit 148B prevents the second state machine from transitioning to the first boost output mode 200B until the minimum time indicator is de-asserted. Once both the minimum charge time indicator are de-asserted and the first boost level indication is asserted, the logic circuit 148B configures the second state machine to transition to the first boost output mode 200A, resets the counter output of the boost time counter 186, and enables the boost time counter 186 to begin counting up. Otherwise, the second state machine remains in the shunt output mode 198B.

[00172] In the first boost output mode 200B, the logic circuit 148B

configures the series switch control output 162 such that the series switch 70 is in an open state (not conducting). The logic circuit 148B also configures the shunt switch control output 164 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 1 48B configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 to be in a first boost mode of operation to provide 1 .5 x V_BAT at the charge pump output 64. As a result, the switching voltage output 26 of Figure 3B is configured to provide a switching voltage, V_Sw, substantially equal to 1 .5 x V_BAT- In response to de- assertion of the first boost level indication 1 54B, which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_COMP', is less than the first boost level threshold 1 28, the logic circuit 1 48B configures the second state machine to transition to the shunt output mode 1 98B. If the count output of the boost time counter 1 86 exceeds the maximum boost time parameter, the logic circuit 1 48B asserts a minimum charge time indicator. In response to the minimum charge time indicator being asserted, the logic circuit 1 48B sets the count value of the boost lockout counter 1 84 and enables the boost lockout counter 1 84 to begin counting down. However, in response to assertion of the second boost level indication 1 56B which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_COMP', is greater than or equal to the scaled second boost level threshold 1 82, the logic circuit 1 48B configures the second state machine to transition to the second boost output mode 202B. Otherwise, the second state machine remains in the first boost output mode 200B.

[00173] In the second boost output mode 202B, the logic circuit 1 48B configures the series switch control output 1 62 such that the series switch 70 is in an open state (not conducting). The logic circuit 1 48B also configures the shunt switch control output 1 64 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 1 48B configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 to be in a second boost mode of operation to provide 2 x V_BAT at the charge pump output 64. As a result, switching voltage output 26 of Figure 3B is configured to provide a switching voltage, V_Sw, substantially equal to 2 x V_BAT- [00174] In response to de-assertion of the first boost level indication 1 54B which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_COMP', is less than the scaled first boost level threshold 1 80, the logic circuit 148B configures the second state machine to transition to the series output mode 1 98B. If the count output of the boost time counter 1 86 exceeds the maximum boost time parameter, the logic circuit 148B asserts a minimum charge time indicator. In response to the minimum charge time indicator being asserted, the logic circuit 148 sets the count value of the boost lockout counter 1 84 and enables the boost lockout counter 184 to begin counting down. Otherwise, the second state machine remains in the second boost output mode 202B.

[00175] Figure 3C depicts an embodiment of the pseudo-envelop follower power management system 1 0B of Figure 1 B that does not include a frequency lock loop (FLL) circuit. The embodiment of the pseudo-envelop follower power management system 1 0B that does not include a frequency lock loop (FLL) circuit may include a switcher control circuit 52C. The switcher controlcontroller circuit 52C may include a threshold detector and control circuit 1 32C, which is similar to the threshold detector circuit 1 32B of Figure 3B. However, unlike threshold detector circuit 1 32B, the threshold detector and control circuitl 32C may not be configured to provide the logic level indication of the switching voltage output, V_SW_EST_OUT, to an FLL circuit. Likewise, unlike threshold detector circuit 1 32B, the threshold detector 1 32C may not be configured to receive threshold scalar from an FLL circuit.

[00176] Figure 4C depicts an embodiment of the threshold detector and control circuit 132C. Similar to the threshold detector and control circuit 1 32B of Figure 4B, the threshold detector and control circuit 1 32C includes a summing circuit 1 36 configured to receive the threshold offset current, ITHRESHOLD_OFFSET, 42 and the power amplifier circuit output current estimate, I PAWA_OUT_EST, 40 generated by the parallel amplifier circuit. The summing circuit 1 36 subtract the threshold offset current, ITHRESHOLD_OFFSET, 42 from the parallel amplifier circuit output current estimate, I PAWA_OUT_EST, 40 to generate a compensated parallel amplifier circuit output current estimate, I PAWA_COMP'- AS discussed before, the threshold offset current, ITHRESHOLD_OFFSET, may be used to control the offset voltage, VQFFSET, that is generated across the coupling circuit 1 8, as depicted in Figure 1 A. In the case where the coupling circuit 1 8 is a wire, such that the amplifier output 32A is directly coupled to the power amplifier supply node 28, the VOFFSET IOOP circuit 41 and the threshold offset current, ITHRESHOLD_OFFSET, are omitted such that I PAWA_COMP' is the same as parallel amplifier circuit output current estimate, I PAWA OUT EST, 40.

[00177] As depicted in Figure 4C, with continuing reference to Figures 1 A and 3C, the threshold detector and control circuit 1 32C may include a first comparator 140, a second comparator 142, a third comparator 144, a fourth comparator 146, and a logic circuit 148C. The example embodiment of the logic circuit 148C may include a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gates or transistor logic, discrete hardware components, or any combination thereof designed to perform. Some

embodiments of the logic circuit 148C may be implemented in either a digital or analog processor.

[00178] The first comparator 140 includes a positive terminal coupled to the shunt level threshold 1 24, a negative terminal coupled to the compensated parallel amplifier circuit output current estimate, I PAWA_COMP', and a first comparator output configured to generate a shunt level indication 1 50C, which is provided to the logic circuit 148C. When the compensated parallel amplifier circuit output current estimate, I PAWA_COMP', is greater than or equal to the shunt level threshold 1 24, the shunt level indication 1 50C is asserted. When the compensated parallel amplifier circuit output current estimate, I PAWA_COMP', is less than the shunt level threshold 1 24, the shunt level indication 1 50C is de- asserted. The second comparator 142 includes a positive terminal coupled to the series level threshold 1 26, a negative terminal coupled to the compensated parallel amplifier circuit output current estimate, I PAWA COMP_J' and a second comparator output configured to generate a series level indication 1 52C, which is provided to the logic circuit 148C. When the compensated parallel amplifier circuit output current estimate, I PAWA_COMP,' is greater than or equal to the series level threshold 1 26, the series level indication 1 52C is asserted. When the compensated parallel amplifier circuit output current estimate, I PAWA_COMP,' is less than the series level threshold 1 26, the series level indication 1 50C is de- asserted. The third comparator 144 includes a positive terminal coupled to the first boost level threshold 1 28, a negative terminal coupled to the compensated parallel amplifier circuit output current estimate, I PAWA_COMP', and a third comparator output configured to generate a first boost level indication 1 54C which is provided to the logic circuit 148C. When the compensated parallel amplifier circuit output current estimate, I PAWA_COMP', is greater than the first boost level threshold 1 28, the first boost level indication 1 54C is asserted. When the compensated parallel amplifier circuit output current estimate, I PAWA_COMP,' is less than the first boost level threshold 1 28, the first boost level indication 1 54C is de- asserted. The fourth comparator 146 includes a positive terminal coupled to the second boost level threshold 1 30, a negative terminal coupled to the

compensated parallel amplifier circuit output current estimate, I PAWA COMP_J' and a fourth comparator output configured to generate a second boost level indication 1 56C, which is provided to the logic circuit 148C. When the compensated parallel amplifier circuit output current estimate, I PAWA_COMP,' is greater than the second boost level threshold 1 30, the second boost level indication 1 56C is asserted. When the compensated parallel amplifier circuit output current estimate, I PAWA_COMP,' is less than the second boost level threshold 1 30, the second boost level indication 1 56C is de-asserted.

[00179] Similar to the logic circuit 148A of Figure 4A, the logic circuit 148B, the logic circuit 148C may be configured to generate a series switch control output 1 62 provided to the first output buffer 1 58, a shunt switch control output 1 64 provided to the second output buffer 1 60, one or more switching voltage output cmos signals, V_Sw_ _EST_CMOS_SIGNAL(S), 166 provided to the third output buffer 1 61 , and a switching voltage output, V_SW_EST, 38B. As previously described, the series switch control output 1 62, a shunt switch control output 1 64, and the one or more switching voltage output cmos signals, may be configured to operate with the first output buffer 1 58, the second output buffer 1 60, and the third output buffer 1 61 to generate the series switch control signal 66, the shunt switch control signal 69, and the switching voltage output, V_SW_EST, 38B, respectively. Similar to the logic circuit 148A of Figure 4A and the logic circuit 148B of Figure 4B, the logic circuit 148C may include a boost lockout counter 184 and a boost time counter 186. The operation of the boost lockout counter 184 and a boost time counter 186 of the logic circuit 148C is substantially similar to the operation of the boost lockout counter 184 and a boost time counter 186 of the logic circuit 148A and 148B.

[00180] Similar to the threshold detector and control circuit 132A of Figure 4A and the threshold detector and control circuit 132B, the threshold detector and control circuit 132C may be configured to receive mode switch control signal 131 from the controller 50 in order to configure logic circuit 148C to operate the multi-level charge pump buck converter in different modes of operation. As an example, the mode switch control signal 131 may configure operation of a state machine within the threshold detector and control circuit 132C that governs how the switching voltage output 26 transitions the switching voltage output 26 to provide different output levels. As a first example embodiment of a state machine within the threshold detector and control circuit 132C, the mode switch control signal 131 may configure the multi-level charge pump buck converter 12 to operate in a first mode of operation, depicted in Figure 5C. As another example embodiment a state machine within the threshold detector and control circuit 132C, the mode switch control signal 131 may configure the multi-level charge pump buck converter 12 to operate in a second mode of operation, depicted in Figure 6C.

[00181] The operation of the logic circuit 148C will now be discussed with continuing reference to Figures 1 A, 3C, 4C, 5C, 6C, and 7. Similar to the logic circuit 148A of Figure 4A and the logic circuit 148A of Figure 4B, the logic circuit 148C. The logic circuit 148C may be digital or analog based logic configured for one or more state machines of the threshold detector and control circuit 132C.

[00182] Operation of the first state machine implemented in the logic circuit 148C, which depicted in Figure 5C, will now be described. The first state machine includes a shunt output mode 188C, a series output mode 190C, a first boost output mode 192C, and a second boost output mode 194C. [00183] In the shunt output mode 1 88C, the logic circuit 1 48C (Figure 4C) configures the series switch control output 1 62 such that the series switch 70 (Figure 3C) is in an open state (not conducting). The logic circuit 1 48C also configures the shunt switch control output 1 64 such that the shunt switch 72 is in a closed state (conducting). In addition, the logic circuit 1 48C configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 (Figure 3C) to be in a charging mode of operation. As a result, switching voltage output 26 of Figure 3C is configured to provide a switching voltage, V_Sw, substantially equal to ground. In response to assertion of the series level indication 1 52C, which indicates that the compensated parallel amplifier circuit output current estimate, IPAWA_COMP, is greater than or equal to the series level threshold 1 26, the logic circuit 1 48C configures the first state machine to transition to the series output mode 1 90C. Otherwise the state machine remains in the shunt output mode 1 88C.

[00184] In the series output mode 1 90C, the logic circuit 1 48 C configures the series switch control output 1 62 such that the shunt switch 70 is in a closed state (conducting). The logic circuit 1 48C also configures the shunt switch control output 1 64 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 1 48C configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 to be in a charging mode of operation. As a result, switching voltage output 26 of Figure 3C is configured to provide a switching voltage, V_Sw, substantially equal to the direct current (DC) voltage, V_BAT-

[00185] In response to de-assertion of the shunt level indication 1 50 (Figure 4C), which indicates that the compensated parallel amplifier circuit output current estimate, IPAWA_COMP,' is less than the shunt level threshold 1 24, the logic circuit 1 48C configures the first state machine to transition to the shunt output mode 1 88C (Figure 5C). However, in response to assertion of the first boost level indication 1 54C, which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_COMP, is greater than or equal to the first boost level threshold 1 28, the logic circuit 1 48C configures the first state machine to transition to the first boost output mode 192C. Otherwise, the first state machine remains in the series output mode 190C.

[00186] In the first boost output mode 192C, the logic circuit 148C (Figure 4C) configures the series switch control output 162 such that the series switch 70 (Figure 3C) is in an open state (not conducting). The logic circuit 148C also configures the shunt switch control output 164 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 148C configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 to be in a first boost mode of operation to provide 1 .5 x V_BAT at the charge pump output 64. As a result, switching voltage output 26 of Figure 3A is configured to provide a switching voltage, V_Sw, substantially equal to 1 .5 x V_BAT- In response to de-assertion of the shunt level indication 150C (Figure 4C), which indicates that the compensated parallel amplifier circuit output current estimate, IPAWA_COMP,' is less than the shunt level threshold 124, the logic circuit 148C configures the first state machine to transition to the shunt output mode 188C (Figure 5C). However, in response to assertion of the second boost level indication 156C, which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_COMP,' is greater than or equal to the second boost level threshold 130, the logic circuit 148A configures the first state machine to transition to the second boost output mode 194C. Otherwise, the first state machine remains in the first boost output mode 192C.

[00187] In the second boost output mode 194C, the logic circuit 148C (Figure 4C) configures the series switch control output 162 such that the series switch 70 (Figure 3C) is in an open state (not conducting). The logic circuit 148C also configures the shunt switch control output 164 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 148C

configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 to be in a second boost mode of operation to provide 2 x VBAT at the charge pump output 64. As a result, the switching voltage output 26 of Figure 3C is configured to provide a switching voltage, V_Sw, substantially equal to 2 x VBAT- In response to de-assertion of the shunt level indication 150C, which indicates that the compensated parallel amplifier circuit output current estimate, l pAWA_coMp', is less than the shunt level threshold 124, the first state machine transitions to the shunt output mode 188C. Otherwise, the state machine remains in the second boost output mode 194C.

[00188] Operation of the second state machine of the logic circuit 148A, which is depicted in Figure 6C, will now be described. The second state machine includes a shunt output mode 196C, a series output mode 198C, a first boost output mode 200C, and a second boost output mode 202C. In addition, the second state machine uses the above described boost lockout counter 184 and boost time counter 186 of the logic circuit 148C.

[00189] In the shunt output mode 196C, the logic circuit 148C (Figure 4C) configures the series switch control output 162 such that the series switch 70 is in an open state (not conducting). The logic circuit 148C also configures the shunt switch control output 164 such that the shunt switch 72 is in a closed state (conducting). In addition, the logic circuit 148C configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 (Figure 3C) to be in a charging mode of operation. As a result, switching voltage output 26 of Figure 3C is configured to provide a switching voltage, V_Sw, substantially equal to ground. If the boost lockout counter 184 is enabled, the boost lockout counter 184 continues to count down. In response to assertion of the series level indication 152C, which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_COMP,' is greater than or equal to the series level threshold 126, the second state machine transitions to the series output mode 198C. Otherwise the second state machine remains in the shunt output mode 196C.

[00190] In the series output mode 198C, the logic circuit 148C (Figure 4C) configures the series switch control output 162 such that the series switch 70 is in a closed state (conducting). The logic circuit 148C also configures the shunt switch control output 164 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 148C configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 to be in a charging mode of operation. As a result, switching voltage output 26 of Figure 3C is configured to provide a switching voltage, V_Sw, substantially equal to the direct current (DC) voltage, V_BAT- If the boost lockout counter 184 is enabled, the boost lockout counter 184 continues to count down. In response to de-assertion of the shunt level indication 150C, which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_COMP,' is less than the shunt level threshold 124, the logic circuit 148C configures the second state machine to transition to the shunt output mode 196C. However, in response to assertion of the first boost level indication 154C, which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_COMP'_J is greater than or equal to the first boost level threshold 128, the logic circuit 148C determines whether both the minimum charge time indicator is de-asserted and the first boost level indication is asserted. If the minimum charge time indicator is de- asserted and the first boost level indication is asserted, the logic circuit 148C configures the second machine to transition to the first boost output mode 200C. Otherwise, the logic circuit 148C prevents the second state machine from transitioning to the first boost output mode 200C until the minimum time indicator is de-asserted. Once both the minimum charge time indicator are de-asserted and the first boost level indication154C is asserted, the logic circuit 148C configures the second state machine to transition to the first boost output mode 200C, resets the counter output of the boost time counter 186, and enables the boost time counter 186 to begin counting up. Otherwise, the second state machine remains in the shunt output mode 198C.

[00191 ] In the first boost output mode 200C, the logic circuit 148C configures the series switch control output 162 such that the series switch 70 is in an open state (not conducting). The logic circuit 148C also configures the shunt switch control output 164 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 148C configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 (Figure 3C) to be in a first boost mode of operation 200C to provide 1 .5 x V_BAT at the charge pump output 64. As a result, the switching voltage output 26 of Figure 3C is configured to provide a switching voltage, V_Sw, substantially equal to 1 .5 x VBAT- In response to de-assertion of the first boost level indication 1 54C, which indicates that the compensated parallel amplifier circuit output current estimate, l pAWA_coMp', is less than the first boost level threshold 1 28, the logic circuit 1 48C configures the second state machine to transition to the shunt output mode 1 98C. If the count output of the boost time counter 1 86 exceeds the maximum boost time parameter, the logic circuit 1 48C asserts a minimum charge time indicator. In response to the minimum charge time indicator being asserted, the logic circuit 1 48C sets the count value of the boost lockout counter 1 84 and enables the boost lockout counter 1 84 to begin counting down. However, in response to assertion of the second boost level indication 1 56C, which indicates that the compensated parallel amplifier circuit output current estimate, l pAWA_coMp', is greater than or equal to the second boost level threshold 1 30, the logic circuit 1 48C configures the second state machine to transition to the second boost output mode 202C. Otherwise, the second state machine remains in the first boost output mode 200C.

[00192] In the second boost output mode 202C, the logic circuit 1 48C configures the series switch control output 1 62 such that the series switch 70 is in an open state (not conducting). The logic circuit 1 48C also configures the shunt switch control output 1 64 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 1 48C configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 (Figure 3C) to be in a second boost mode of operation 200C to provide 2 x V_BAT at the charge pump output 64. As a result, switching voltage output 26 of Figure 3C is configured to provide a switching voltage, V_Sw, substantially equal to 2 x V_BAT- [00193] In response to de-assertion of the first boost level indication 1 54C, which indicates that the compensated parallel amplifier circuit output current estimate, IPAWA_COMP', is less than the first boost level threshold 1 28, the logic circuit 1 48C configures the second state machine to transition to the series output mode 1 98C. If the count output of the boost time counter 1 86 exceeds the maximum boost time parameter, the logic circuit 1 48C asserts a minimum charge time indicator. In response to the minimum charge time indicator being asserted, the logic circuit 148C sets the count value of the boost lockout counter 184 and enables the boost lockout counter 184 to begin counting down. Otherwise, the second state machine remains in the second boost output mode 202C.

[00194] The threshold and control circuit 132C further provides a logic level indication of the switching voltage output , V_SW_EST_OUT, which is a logic level representation of the switching voltage output , V_Sw_. The switching voltage output , VSW_EST_OUT, may be based upon the V_SW_EST_CMOS_SIGNAL(S). In some embodiment of threshold and control circuit 132A, the a logic level indication of the switching voltage output , V_SW_EST_OUT, may be asserted when multi-level charge pump buck converter 12 is in either the series output mode, the first boost output mode, or the second boost output mode. The logic level indication of the switching voltage output , V_Sw_ _EST_OUT_J is de-asserted when the multi-level charge pump buck converter 12 is in the shunt output mode of operation.

[00195] Figure 3D depicts another embodiment of the embodiment of the pseudo-envelop follower power management system 10B of Figure 1 B that includes neither a frequency lock loop (FLL) circuit nor a VOFFSET Loop Circuit 41 . In addition, Figure 3D depicts another embodiment of the embodiment of the pseudo-envelop follower power management system 10B of Figure 1 B where the coupling circuit 18 is a wire and the amplifier output 32A of the parallel amplifier circuit 14 is directly coupled to the power amplifier supply node 28.

[00196] Figure 3C depicts an embodiment of the multi-level charge pump buck converter having a switcher control circuit 52D, which is similar to the a switcher control circuit 52C depicted in Figure 3C. However, unlike the switcher control circuit 54C, the switcher control circuit 54D includes a threshold detector and control circuit 132D that is not configured to receive the threshold offset current, ITHRESHOLD_OFFSET, 42 from the parallel amplifier circuit.

[00197] Similar to the threshold detector and control circuit 132A of Figure 4A, the threshold detector and control circuit 132B, and the threshold detector and control circuit 132B, the threshold detector and control circuit 132C of Figure 4C, the threshold detector and control circuit 132D may be configured to receive mode switch control signal 1 31 from the controller 50 in order to configure logic circuit 148D to operate the multi-level charge pump buck converter in different modes of operation. As an example, the mode switch control signal 1 31 may configure operation of a state machine within the threshold detector and control circuit 1 32D that governs how the switching voltage output 26 transitions the switching voltage output 26 to provide different output levels. As a first example embodiment of a first state machine within the threshold detector and control circuit 1 32D, the mode switch control signal 131 may configure the multi-level charge pump buck converter 1 2 to operate in a first mode of operation, depicted in Figure 5D. As another example embodiment a second state machine within the threshold detector and control circuit 1 32D, the mode switch control signal 1 31 may configure the multi-level charge pump buck converter 1 2 to operate in a second mode of operation, depicted in Figure 6D.

[00198] One embodiment of the threshold detector and control circuit 1 32D is depicted in Figure 4D. The threshold detector and control circuit 1 32D is similar to the threshold detector and control circuit 54A, depicted in Figure 4A, except the logic circuit 148A is replace by a logic circuit 148D and the parallel amplifier circuit output current estimate, I PAWA_COMP_J is replaced by the parallel amplifier circuit output current estimate, I PAWA_OUT_EST, 40. As discussed above, power amplifier circuit output current estimate, I PAWA_OUT_EST; 40 may include the power amplifier circuit output current estimate, I PAWA_OUT_EST, 40 includes the scaled parallel amplifier output current estimate, I PARA AMP SENSE_J cind the scaled open loop assist circuit output current estimate, I ASSIST SENSE- However, in some embodiments of the parallel amplifier circuit that do not include the open loop assist circuit 39, the parallel amplifier circuit output current estimate,

I PAWA_OUT_EST, 40 only includes the scaled parallel amplifier output current estimate, I PARA_AMP_SENSE, generated by the parallel amplifier sense circuit 36 of the parallel amplifier circuit 32, which is discussed above.

[00199] The threshold detector and control circuit 1 32D of Figure 4D will be described with continuing reference to Figure 3D. The threshold detector and control circuit 132D may include a first comparator 140, a second comparator 142, a third comparator 144, a fourth comparator 146, and a logic circuit 148A. The example embodiment of the logic circuit 148A may include a Field

Programmable Gate Array (FPGA) or other programmable logic device, discrete gates or transistor logic, discrete hardware components, or any combination thereof designed to perform. Some embodiments of the logic circuit 148D may be implemented in either a digital or analog processor.

[00200] The first comparator 140 includes a positive terminal coupled to the shunt level threshold 124, a negative terminal coupled to the parallel amplifier circuit output current estimate, I PAWA_OUT_EST, and a first comparator output configured to generate a shunt level indication 1 50D, which is provided to the logic circuit 148A. When the parallel amplifier circuit output current estimate, lpAWA_ouT_EST, is greater than or equal to the shunt level threshold 1 24, the shunt level indication 1 50D is asserted. When the parallel amplifier circuit output current estimate, I PAWA_OUT_EST, is less than the shunt level threshold 1 24, the shunt level indication 1 50D is de-asserted. The second comparator 142 includes a positive terminal coupled to the series level threshold 126, a negative terminal coupled to the parallel amplifier circuit output current estimate, I PAWA OUT EST, and a second comparator output configured to generate a series level indication 1 52D, which is provided to the logic circuit 148D. When the parallel amplifier circuit output current estimate, I PAWA_OUT_EST, is greater than or equal to the series level threshold 1 26, the series level indication 1 52D is asserted. When the parallel amplifier circuit output current estimate, I PAWA_OUT_EST, is less than the series level threshold 126, the series level indication 1 50D is de-asserted. The third comparator 144 includes a positive terminal coupled to the first boost level threshold 128, a negative terminal coupled to the parallel amplifier circuit output current estimate, I PAWA_OUT_EST, and a third comparator output configured to generate a first boost level indication 1 54D, which is provided to the logic circuit 148D. When the parallel amplifier circuit output current estimate, I PAWA_OUT_EST, is greater than the first boost level threshold 1 28, the first boost level indication 1 54D is asserted. When the parallel amplifier circuit output current estimate, IpAWA OUT EST, is less than the first boost level threshold 128, the first boost level indication 154D is de-asserted. The fourth comparator 146 includes a positive terminal coupled to the second boost level threshold 130, a negative terminal coupled to the parallel amplifier circuit output current estimate, I PAWA_OUT_EST, and a fourth comparator output configured to generate a second boost level indication 156D, which is provided to the logic circuit 148D. When the parallel amplifier circuit output current estimate, IPAWA_OUT_EST, is greater than the second boost level threshold 130, the second boost level indication 156D is asserted. When the parallel amplifier circuit output current estimate, IPAWA_OUT_EST, is less than the second boost level threshold 130, the second boost level indication 156D is de- asserted.

[00201 ] Similar to the logic circuit 148A of Figure 4A, the logic circuit 148B, and the logic circuit 148C of Figure 4C, the logic circuit 148D may aslo be configured to generate a series switch control output 162 provided to the first output buffer 158, a shunt switch control output 164 provided to the second output buffer 160, one or more switching voltage output cmos signals,

VSW_EST_CMOS_SIGNAL(S),166 provided to the third output buffer 161 , and a switching voltage output, V_SW_EST, 38B. As previously described, the series switch control output 162, a shunt switch control output 164, and the one or more switching voltage output cmos signals, may be configured to operate with the first output buffer 158, the second output buffer 160, and the third output buffer 161 to generate the series switch control signal 66, the shunt switch control signal 69, and the switching voltage output, V_SW_EST, 38B, respectively. Also similar to the logic circuit 148A of Figure 4A, the logic circuit 148B, and the logic circuit 148C of Figure 4C, the logic circuit 148d may include a boost lockout counter 184 and a boost time counter 186. The operation of the boost lockout counter 184 and a boost time counter 186 of the logic circuit 148D is substantially similar to the operation of the boost lockout counter 184 and a boost time counter 186 of the logic circuit 148A ,148B, and 148C.

[00202] The example embodiment of the logic circuit 148D may include a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gates or transistor logic, discrete hardware components, or any combination thereof designed to perform. Some embodiments of the logic circuit 1 48D may be implemented in either a digital or analog processor. In addition, the logic circuit 148D may include an embodiment of the first state machine and the second state machine of the threshold detector and control circuit 1 32D.

[00203] Operation of the first state machine implemented in the logic circuit 1 48D, which depicted in Figure 5D, will now be described. The first state machine includes a shunt output mode 1 88D, a series output mode 1 90D, a first boost output mode 1 92D, and a second boost output mode 1 94D.

[00204] In the shunt output mode 1 88D, the logic circuit 1 48D (Figure 4D) configures the series switch control output 1 62 such that the series switch 70 (Figure 3D) is in an open state (not conducting). The logic circuit 1 48D also configures the shunt switch control output 1 64 such that the shunt switch 72 is in a closed state (conducting). In addition, the logic circuit 1 48D configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 (Figure 3D) to be in a charging mode of operation. As a result, switching voltage output 26 of Figure 3D is configured to provide a switching voltage, V_Sw, substantially equal to ground. In response to assertion of the series level indication 1 52D, which indicates that the parallel amplifier circuit output current estimate, I PAWA_OUT_EST, is greater than or equal to the series level threshold 1 26, the logic circuit 1 48D configures the first state machine to transition to the series output mode 1 90D. Otherwise the state machine remains in the shunt output mode 1 88D.

[00205] In the series output mode 1 90D, the logic circuit 1 48D configures the series switch control output 1 62 such that the shunt switch 70 is in a closed state (conducting). The logic circuit 1 48D also configures the shunt switch control output 1 64 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 1 48D configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 to be in a charging mode of operation. As a result, switching voltage output 26 of Figure 3D is configured to provide a switching voltage, V_Sw, substantially equal to the direct current (DC) voltage, V_BAT- [00206] In response to de-assertion of the shunt level indication 1 50D (Figure 4D), which indicates that the power amplifier circuit output current estimate, IPAWA_OUT_EST, is less than the shunt level threshold 1 24, the logic circuit 1 48D configures the first state machine to transition to the shunt output mode 1 88D (Figure 5D). However, in response to assertion of the first boost level indication 1 54D, which indicates that the parallel amplifier circuit output current estimate, IPAWA_OUT_EST, is greater than or equal to the first boost level threshold 1 28, the logic circuit 1 48D configures the first state machine to transition to the first boost output mode 1 92D. Otherwise, the first state machine remains in the series output mode 1 90D.

[00207] In the first boost output mode 1 92D, the logic circuit 1 48D (Figure 4D) configures the series switch control output 1 62 such that the series switch 70 (Figure 3D) is in an open state (not conducting). The logic circuit 1 48D also configures the shunt switch control output 1 64 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 1 48D configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 to be in a first boost mode of operation to provide 1 .5 x V_BAT at the charge pump output 64. As a result, switching voltage output 26 of Figure 3D is configured to provide a switching voltage, V_Sw, substantially equal to 1 .5 x V_BAT- In response to de-assertion of the shunt level indication 1 50D (Figure 4D), which indicates that the parallel amplifier circuit output current estimate, IPAWA_OUT_EST, is less than the shunt level threshold 1 24, the logic circuit 1 48D configures the first state machine to transition to the shunt output mode 1 88D (Figure 5D).

However, in response to assertion of the second boost level indication 1 56D, which indicates that the parallel amplifier circuit output current estimate,

IPAWA_OUT_EST, is greater than or equal to the second boost level threshold 1 30, the logic circuit 148D configures the first state machine to transition to the second boost output mode 1 94D. Otherwise, the first state machine remains in the first boost output mode 1 92D.

[00208] In the second boost output mode 1 94D, the logic circuit 1 48D

(Figure 4D) configures the series switch control output 1 62 such that the series switch 70 (Figure 3D) is in an open state (not conducting). The logic circuit 1 48D also configures the shunt switch control output 1 64 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 1 48D

configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 to be in a second boost mode of operation to provide 2 x VBAT at the charge pump output 64. As a result, the switching voltage output 26 of Figure 3D is configured to provide a switching voltage, V_Sw, substantially equal to 2 x VBAT- In response to de-assertion of the shunt level indication 1 50D, which indicates that the parallel amplifier circuit output current estimate, IPAWA_OUT_EST, is less than the shunt level threshold 1 24, the first state machine transitions to the shunt output mode 1 88D. Otherwise, the state machine remains in the second boost output mode 1 94D.

[00209] Operation of the second state machine of the logic circuit 1 48D, which is depicted in Figure 6D, will now be described. The second state machine includes a shunt output mode 1 96D, a series output mode 1 98D, a first boost output mode 200D, and a second boost output mode 202D. In addition, the second state machine uses the above described boost lockout counter 1 84 and boost time counter 1 86 of the logic circuit 148D.

[00210] In the shunt output mode 1 96D, the logic circuit 1 48D (Figure 4D) configures the series switch control output 1 62 such that the series switch 70 is in an open state (not conducting). The logic circuit 1 48D also configures the shunt switch control output 1 64 such that the shunt switch 72 is in a closed state (conducting). In addition, the logic circuit 1 48D configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 (Figure 3D) to be in a charging mode of operation. As a result, switching voltage output 26 of Figure 3D is configured to provide a switching voltage, V_Sw, substantially equal to ground. If the boost lockout counter 1 84 is enabled, the boost lockout counter 1 84 continues to count down. In response to assertion of the series level indication 1 52D, which indicates that the parallel amplifier circuit output current estimate, IPAWA_OUT_EST, is greater than or equal to the series level threshold 1 26, the second state machine transitions to the series output mode 1 98D. Otherwise the second state machine remains in the shunt output mode 1 96D.

[00211] In the series output mode 1 98D, the logic circuit 1 48D (Figure 4D) configures the series switch control output 1 62 such that the series switch 70 is in a closed state (conducting). The logic circuit 1 48D also configures the shunt switch control output 1 64 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 1 48D configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 to be in a charging mode of operation. As a result, switching voltage output 26 of Figure 3D is configured to provide a switching voltage, V_Sw, substantially equal to the direct current (DC) voltage, V_BAT- If the boost lockout counter 1 84 is enabled, the boost lockout counter 1 84 continues to count down. In response to de-assertion of the shunt level indication 1 50D, which indicates that the parallel amplifier circuit output current estimate, IPAWA_OUT_EST, is less than the shunt level threshold 1 24, the logic circuit 1 48D configures the second state machine to transition to the shunt output mode 1 96D. However, in response to assertion of the first boost level indication 1 54D, which indicates that parallel amplifier circuit output current estimate, I PAWA_OUT_EST, is greater than or equal to the first boost level threshold 1 28, the logic circuit 1 48D determines whether both the minimum charge time indicator is de-asserted and the first boost level indication is asserted. If the minimum charge time indicator is de-asserted and the first boost level indication is asserted, the logic circuit 1 48D configures the second machine to transition to the first boost output mode 200D. Otherwise, the logic circuit 1 48D prevents the second state machine from transitioning to the first boost output mode 200D until the minimum time indicator is de-asserted. Once both the minimum charge time indicator are de-asserted and the first boost level indication 1 54D is asserted, the logic circuit 1 48D configures the second state machine to transition to the first boost output mode 200D, resets the counter output of the boost time counter 1 86, and enables the boost time counter 1 86 to begin counting up. Otherwise, the second state machine remains in the shunt output mode 1 98D. [00212] In the first boost output mode 200D, the logic circuit 148D configures the series switch control output 162 such that the series switch 70 is in an open state (not conducting). The logic circuit 148D also configures the shunt switch control output 164 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 148D configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 to be in a first boost mode of operation 200D to provide 1 .5 x V_BAT at the charge pump output 64. As a result, the switching voltage output 26 of Figure 3D is configured to provide a switching voltage, V_Sw, substantially equal to 1 .5 x V_BAT- In response to de-assertion of the first boost level indication 154D, which indicates that the parallel amplifier circuit output current estimate, IPAWA_OUT_EST, is less than the first boost level threshold 128, the logic circuit 148D configures the second state machine to transition to the shunt output mode 198D. If the count output of the boost time counter 186 exceeds the maximum boost time parameter, the logic circuit 148D asserts a minimum charge time indicator. In response to the minimum charge time indicator being asserted, the logic circuit 148D sets the count value of the boost lockout counter 184 and enables the boost lockout counter 184 to begin counting down. However, in response to assertion of the second boost level indication 156D, which indicates that the parallel amplifier circuit output current estimate, IPAWA_OUT_EST, is greater than or equal to the second boost level threshold 130, the logic circuit 148D configures the second state machine to transition to the second boost output mode 202D. Otherwise, the second state machine remains in the first boost output mode 200D.

[00213] In the second boost output mode 202D, the logic circuit 148D configures the series switch control output 162 such that the series switch 70 is in an open state (not conducting). The logic circuit 148D also configures the shunt switch control output 164 such that the shunt switch 72 is in an open state (not conducting). In addition, the logic circuit 148D configures the charge pump mode control signal 60 to instruct the multi-level charge pump circuit 56 (Figure 3a) to be in a second boost mode of operation 200D to provide 2 x V_BAT at the charge pump output 64. As a result, switching voltage output 26 of Figure 3D is configured to provide a switching voltage, V_Sw, substantially equal to 2 x V_BAT- [00214] In response to de-assertion of the first boost level indication 1 54D, which indicates that the parallel amplifier circuit output current estimate,

I PAWA_OUT_EST, is less than the first boost level threshold 128, the logic circuit

148D configures the second state machine to transition to the series output mode 1 98D. If the count output of the boost time counter 1 86 exceeds the maximum boost time parameter, the logic circuit 148D asserts a minimum charge time indicator. In response to the minimum charge time indicator being asserted, the logic circuit 148D sets the count value of the boost lockout counter 1 84 and enables the boost lockout counter 184 to begin counting down. Otherwise, the second state machine remains in the second boost output mode 202D.

[00215] Returning to Figure 2A, the parallel amplifier circuit 32 includes a parallel amplifier 35 and a parallel amplifier sense circuit 36. The parallel amplifier 35 includes an amplifier output 32A that generates a parallel amplifier output, VPARA_AMP- In addition, the parallel amplifier 35 outputs a parallel amplifier output current I PARA_AMP- The parallel amplifier sense circuits may include current mirror circuits are in communication with the parallel amplifier 35. Based upon the parallel amplifier output current, I PARA_AMP, the parallel amplifier sense circuit 36 generates a scaled parallel amplifier output current estimate, I PARA_AMP_SENSE, which provides an indication of the parallel amplifier output current I PARA_AMP- A first copy of the scaled parallel amplifier output current estimate, I PARA_AMP_SENSE, is provided to the parallel amplifier output impedance compensation circuit 37. A second copy of the scaled parallel amplifier output current estimate,

I PARA_AMP_SENSE_J is combined with the scaled open loop assist circuit output current estimate, IASSIST_SENSE, to generate the parallel amplifier circuit output current estimate, I PAWA_OUT_EST, 40, which is provided to the multi-level charge pump buck converter 12.

[0021 6] Figure 1 2A depicts one embodiment of the parallel amplifier 35 as the parallel amplifier 35A. The parallel amplifier 35A depicts one embodiment of an AB class amplifier. The parallel amplifier 35A includes a parallel amplifier input voltage 204, a first amplifier, AMP_A, 206, a second amplifier, AMP_B, 208, a first output stage 210, and an amplifier feedback node 212. The parallel amplifier input voltage 204 may be configured to receive either the V_RAMP signal or the compensated V_RAMP signal, V_RAMp_c.

[00217] The first amplifier, AMP_A, 206, includes a positive input terminal 206A, a negative input terminal 206B, and an output terminal 206C. Regarding the first amplifier, AMP_A> 206, the positive input terminal 206A may be coupled to the parallel amplifier input voltage 204. The negative input terminal 206B may be coupled to the amplifier feedback node 212, which is coupled to the power amplifier supply voltage, Vcc. A first resistor, R_A, and a first capacitor, C_A, are arranged in series between the output terminal 206C and the amplifier feedback node 212. The first resistor, R_A, and the first capacitor, C_A, are a feedback network used to extend the operating bandwidth by compensating for the dominant pole introduced by the bypass capacitor, CBYP_ASS, 19. The feedback network may be configured to extend the modulation bandwidth of the first amplifier, AMP_A, 206 out to approximately 30MHz. The first amplifier, AMP_A, 206 generates a first amplifier output voltage, V_A, at the output terminal 206C based upon the difference between the parallel amplifier input voltage 204 appearing at the positive input terminal 206A and the power amplifier supply voltage, Vcc appearing at the negative input terminal 206B.

[00218] Regarding the second amplifier, AMP_B, 208, the positive input terminal 208A may be coupled to the parallel amplifier input voltage 204. The negative input terminal 208B may be coupled to the amplifier feedback node 212, which is coupled to the power amplifier supply voltage, Vcc. A second resistor, RB, and a second capacitor, CB, are arranged in series between the output terminal 208C and the amplifier feedback node 212. The second resistor, R_B, and the second capacitor, C_B, are a feedback network used to extend the operating bandwidth by compensating for the dominant pole introduced by the bypass capacitor, CBYP_ASS, 19. The feedback network may be configured to extend the modulation bandwidth of the second amplifier, AMP_B, 208 out to approximately 30MHz. The second amplifier, AMP_B, 208, generates a second amplifier output voltage, V_B, at the output terminal 208C based upon the difference between the parallel amplifier input voltage 204 appearing at the positive input terminal 208A and the power amplifier supply voltage, Vcc, appearing at the negative input terminal 208B.

[00219] The first output stage 210 includes a first switching element, SW1 _A, 214 and a second switching element, SW1 _B, 216. As a non limiting example, some embodiments of the first switching element, SW1 _A, 214 and the second switching element, SW1 _B, 216 maybe a solid state based switch such as a field effect transistor, an insulator-on-semiconductor based transistor, or a bipolar based transistor. These transistors may operate mainly in Class-AB mode, thus near to linear operation, even though the transistors are referred to as switches. In one example embodiment, the first switching element, SW1 _A, 214 may be a PFET device having a drain 214D, a gate 214G, and a source 214S. Likewise, the second switching element, SW1 _B, 216 may be an NFET device having a drain 216D, a gate 216G, and a source 216S.

[00220] The source 214S of the first switching element, SW 1 _A, 214 may be coupled to the supply input 24 (V_BAT) of the multi-level charge pump buck converter 12. The drain 214D of the first switching element, SW1 _A, 214 may be coupled to the drain 216D of the second switching element, SW1 _B, 216 to form a parallel amplifier output node 218 that provides the parallel amplifier output, Vp_AR_{A A}MP, of the parallel amplifier 35A. The source 216S of the second switching element, SW1 _B, 216 may be coupled to ground.

[00221] The gate 214G of the first switching element, SW1 _A, 214 may be coupled to the output terminal 206C of the first amplifier, AMP_A, 206 in order to receive the first amplifier output voltage, V_A. Similarly, the gate 216G of the second switching element, SW1 _B, 216 may be coupled to the output terminal 208C of the second amplifier, AMP_B, 208 in order to receive the second amplifier output voltage, V_B.

[00222] The parallel amplifier 35A may be configured to source from the parallel amplifier output node 218 and sink current to the parallel amplifier output node 218 based upon the difference between the difference between the parallel amplifier input voltage 204 (either V _AMP or V_RAMP__C) and the power amplifier supply voltage, Vcc. For example, when the power inductor current, I _{SVV OUT}, delivered by the power inductor 1 6 and the bypass capacitor current, I _BYPASS__CAP, delivered by the bypass capacitor, C_BYPASS, 1 9 are insufficient to supply the output current, Ιουτ, to the linear power amplifier 22, the parallel amplifier 35A turns on the first switching element, SW 1 _A, 214 to provide additional current through the coupling capacitor 1 8A to the power amplifier supply node 28.

However, when the power inductor current, I _{SVV OUT}, delivered by the power inductor 1 6, and the bypass capacitor current, IBYPASS_CAP, from the bypass capacitor, CBYPASS, 1 9 exceed the desired level of output current, Ιουτ, to be delivered to the linear power amplifier 22, the parallel amplifier 35A turns on the second switching element, SW 1 _B, 21 6 to shunt the excess current provided to the power amplifier supply node 28 to ground.

[00223] In the case, as depicted in Figures 2A and 2B, where the parallel amplifier circuit 14A includes an open loop assist circuit 39 providing an open loop assist circuit current, _SSIST, the parallel amplifier 35A compensates for either an excess of current or the lack of current supplied to the power amplifier supply node 28. As an example, when the power inductor current, I _{SVV OUT}, the open loop assist current, _SSIST, and the bypass capacitor current, I _BYPASS__CAP, deliver less than the desired level of output current, Ιουτ, to the linear power amplifier 22, the parallel amplifier 35A turns on the first switching element, SW1 _A, 214 to provide the additional current desired by the linear power amplifier 22. As another example, when the power inductor current, I_{SVV OUT}, the open loop assist current, _SSIST, and the bypass capacitor current, I _BYPASS__CAP, deliver excess current to the power amplifier supply node 28, the parallel amplifier 35A turns on the second switching element, SW1 _B, 21 6 such that the excess current is shunted to ground.

[00224] Figure 1 2B depicts another embodiment of the parallel amplifier 35 as the rechargeable parallel amplifier 35B. Unlike the parallel amplifier 35A of Figure 1 2A, the rechargeable parallel amplifier 35B includes a second output stage 220A, a charge conservation capacitor, CAB, and an output control circuit 230A.

[00225] The second output stage 220A includes a first switching element, SW2_A, 222 and a second switching element, SW2_B, 224. As a non limiting example, some embodiments of the first switching element, SW2_A, 222 and the second switching element, SW2_B, 224 may be a solid state based switch such as a field effect transistor, an insulator-on-semiconductor transistor, or a bipolar based transistor. These transistors operate mainly in Class-AB mode, thus near to linear operation, even though the transistors are referred to as switches. In one example embodiment, the first switching element, SW2_A, 222 may be a PFET device having a drain 222D, a gate 222G, and a source 222S. Likewise, the second switching element, SW2_B, 224 may be an NFET device having a drain 224D, a gate 224G, and a source 224S.

[00226] The source 222S of the first switching element, SW2_A, 222 may be coupled to the charge conservation capacitor, C_AB_. The drain 222D of the first switching element, SW2_A, 222 and the drain 224D of the second switching element, SW2_B, 224 may be coupled to the parallel amplifier output node 218 to form the parallel amplifier output, V_PARA_AMP, of the rechargeable parallel amplifier 35B. The source 224S of the second switching element, SW 2_B, 224 may be coupled to the charge conservation capacitor, C_AB_. AS will be explained in further detail below, when the second switching element SW2_B, 224 of the second output stage 220A may be turned on to sink excess current provided to the power amplifier supply node 28, charge is stored on the charge conservation capacitor, C_AB, to generate a saved charge voltage, V_AB. Similarly, when insufficient current is provided to the power amplifier supply node 28, the first switching element, SW2_A, 222 may be turned on to provide additional current to the power amplifier supply node 28 from the charge conservation capacitor, C_AB- [00227] In order to operate in the linear mode of operation, the range of operation of the first switching element, SW2_A, 222, and the second switching element, SW2_B, 224, must take into consideration a minimum headroom voltage, VHEADROOM, of each device. As an example, the first switching element, SW2_A, 222, may operate in the linear mode provided the parallel amplifier output node 218 that provides the parallel amplifier output, V_PARA_AMP, is less than the saved charge voltage, V_AB, minus the minimum headroom voltage, VHEADROOM- Similarly, the second switching element, SW2_B, 224, may operate in the linear mode provided the parallel amplifier output node 218 that provides the parallel amplifier output, V_PARA_ AMP, is greater than the saved charge voltage, VAB, plus the minimum headroom voltage, VHEADROOM-

[00228] The output control circuit 230A includes a V_A input, V_A_IN , a V_B input, VBJN, a V_AB input, V_AB_IN, and a V_PARA_AMP input, V_PARA_AMPJN. The V_A input, VAJN , may be coupled to the output terminal 206C of the first amplifier, AM PA, 206 to receive the first amplifier output voltage, V_A. The V_B input, V_B_IN , may be coupled to the output terminal 208C of the second amplifier, AM P_B, 208, to receive second amplifier output voltage, V_B. The V_PARA_AMP input, V_PARA_AMP- _IN, may be coupled to the parallel amplifier output node 218 to receive the parallel amplifier output, V_PARA_AMP- The V_AB input, V_AB_IN, may be coupled to the saved charge voltage, V_AB.

[00229] The output control circuit 230A may include a first switch control output, Vsw-iA, a second switch control output, V_Sw2A, a third switch control output, Vsw2B, and a fourth switch control output, V_SW-I B- The first switch control output, Vsw-iA, may be coupled to the gate 214G of the first switching element, SW1 A, 214. The second switch control output, V_Sw2A, may be coupled to the gate 222G of the first switching element, SW2_A, 222. The third switch control output, Vsw2B, may be coupled to the gate 224G of the second switching element, SW2_B, 224. The fourth switch control output, V_SW-I B, may be coupled to the gate 216G of the second switching element, SW1 _B, 216.

[00230] The output control circuit 230A selectively couples the V_A input, VAIN , to either the first switch control output, V_SW-IA, or the second switch control output, Vsw2A, based upon the minimum headroom voltage, VHEADROOM, the saved charge voltage, V_AB, and the parallel amplifier output, V_PARA_AMP- For example, when the parallel amplifier output, V_PARA_ AMP, is greater than the saved charge voltage, V_AB, minus the minimum headroom voltage, VHEADROOM, the output control circuit 230A couples the V_A input, V_A_IN , to the first switch control output, Vsw-iA, of the first output stage 21 0 and sets the second switch control output, Vsw2A, to disable the first switching element , SW₂A, 222 of the second output stage 220A. As an example, the output control circuit 230A may pull up the second switch control output, V_Sw2A, to the saved charge voltage, V_AB. AS a result, the first amplifier output voltage, V_A, is coupled to the gate 214G of the first switching element, SW1 _A, 214 of the first output stage 21 0.

[00231 ] However, when the parallel amplifier output, V_{PARA AM}p, is less than or equal to the saved charge voltage, V_AB, minus the minimum headroom voltage, VHEADROOM, the output control circuit 230A couples the V_A input, V_AJN , to the second switch control output, V_Sw2A, and sets the first switch control output, V_Sw 1 A, to disable the first switching element , SW1 _A, 214 of the first output stage 210. As an example, the output control circuit 230A may pull up the first switch control output, Vsw-iA, to the supply input 24 (V_BAT). AS a result, the first amplifier output voltage, V_A, is coupled to the gate 222G of the first switching element, SW2_A, 222 of the second output stage 220A.

[00232] The output control circuit 230A also selectively couples the V_B input, VE IN , to either the third switch control output, V_Sw2B, or the fourth switch control output, V_SW-I B, based upon the minimum headroom voltage, VHEADROOM, the saved charge voltage, V_AB, and the parallel amplifier output, V_PARA__AMp. . For example, when the parallel amplifier output, V_{PARA A}MP, is greater than the saved charge voltage, V_AB, plus the minimum headroom voltage, VHEADROOM, the output control circuit 230A couples the V_B input, V_BJN , to the third switch control output, Vsw2B, and sets the fourth switch control output, V_SWI B, to disable the second switching element , SW1 _B, 21 6. As an example, the output control circuit 230A may pull down the fourth switch control output, V_SWI B, to the ground. As a result, the second amplifier output voltage, V_B, is coupled to the gate 224G of the second switching element, SW2_B, 224 of the second output stage 220A.

[00233] However, when the parallel amplifier output, V_{PARA AM}p, is less than or equal to the saved charge voltage, V_ABi plus the minimum headroom voltage, VHEADROOM, the output control circuit 230A couples the fourth switch control output, Vsw-i B, to the V_B input, V_BJN , and sets the third switch control output, Vsw2B, to disable the second switching element , SW2_B, 224. As an example, the output control circuit 230A may pull down the third switch control output, V_Sw2B, to ground _.

[00234] Figure 12C depicts another embodiment of the parallel amplifier 35 as the rechargeable parallel amplifier 35C. The rechargeable parallel amplifier 35C of Figure 12C is similar to the rechargeable parallel amplifier 35B of Figure 12B. However, unlike rechargeable parallel amplifier 35B, rechargeable parallel amplifier 35C includes an output control circuit 230B instead of the output control circuit 230A and a second output stage 220B instead of the second output stage 220A. The output control circuit 230B further includes a V_Cc input, V_CC_IN, that is coupled to the power amplifier supply node 28 in order to receive the power amplifier supply voltage, V_Cc- In addition, unlike rechargeable parallel amplifier 35B, in the rechargeable parallel amplifier 35C, the drain 224D of the second switching element, SW2_B, 224 is coupled to the power amplifier supply node 28 instead of being coupled to the parallel amplifier output node 218, which is now labeled as the parallel amplifier output node 218C. Furthermore, as will be explained, the operation of the output control circuit 230B is different from the operation of output control circuit 230A in order to accommodate the coupling of the drain 224D of the second switching element, SW2_B, 224 to the power amplifier supply node 28.

[00235] Similar to the rechargeable parallel amplifier 35B, the rechargeable parallel amplifier 35C must also take into consideration the minimum headroom voltage, VHEADROOM, of the first switching element, SW2_A, 222, and the second switching element, SW2_B, 224, in order to assure the first switching element, SW2_A, 222, and the second switching element, SW2_B, 224, operate in the linear mode. However, because the drain 224D of the second switching element, SW2_B, 224 is coupled to the power amplifier supply node 28, the power amplifier supply voltage, V_Cc, must also be considered.

[00236] Similar to the rechargeable parallel amplifier 35B, the first switching element, SW2_A, 222, of the rechargeable parallel amplifier 35C may operate in the linear mode provided the parallel amplifier output node 21 8C that provides the parallel amplifier output, V_PARA_AMP, is less than the saved charge voltage, VAB_, minus the minimum headroom voltage, VHEADROOM- However, unlike the rechargeable parallel amplifier 35B, the second switching element, SW2_B, 224, of the rechargeable parallel amplifier 35C may operate in the linear mode provided the power amplifier supply voltage, V_Cc, is greater than the saved charge voltage, VAB_, plus the minimum headroom voltage, VHEADROOM- Because the power amplifier supply voltage, V_Cc, tends to be higher than the parallel amplifier output, VPARA_AMP_J the rechargeable parallel amplifier 35C may store additional charge on the charge conservation capacitor, CAB, which increases the charge voltage, V_AB- As a result, the operating range of the first switching element, SW2_A, 222, is also increased.

[00237] Similar to the output control circuit 230A of Figure 1 2B, the output control circuit 230B of Figure 1 2C selectively couples the V_A input, V_A_IN , to either the first switch control output, V_SW-IA, or the second switch control output, Vsw2A, based upon the minimum headroom voltage, VHEADROOM, the saved charge voltage, V_AB, and the parallel amplifier output, V_PARA_ _AMP- For example, when parallel amplifier output, V_PARA_AMP, is greater than the saved charge voltage, V_AB_, minus the minimum headroom voltage, VHEADROOM, the output control circuit 230B couples the V_A input, V_A_IN , to the first switch control output, VswiA, and sets the second switch control output, V_Sw2A, to disable the first switching element , SW2_A, 222 of the second output stage 220B. As an example, the output control circuit 230B may pull up the second switch control output, Vsw2A, to the saved charge voltage, V_AB. AS a result, the first amplifier output voltage, V_A, is coupled to the gate 214G of the first switching element, SW1 A, 214 of the first output stage 21 0C.

[00238] However, when the parallel amplifier output, V_PARA_AMP, is less than or equal to the saved charge voltage, V_AB_, minus the minimum headroom voltage, VHEADROOM, the output control circuit 230B couples the V_A input, V_A_IN , to the second switch control output, V_Sw2A,of the second output stage 220B and sets the first switch control output, V_SWIA, to disable the first switching element , SW1 _A, 214, of the first output stage 210C. As an example, the output control circuit 230B may pull up the first switch control output, V_SWIA, to the supply input 24 (VBAT)_. AS a result, the first amplifier output voltage, V_A, is coupled to the gate 222G of the first switching element, SW2_A, 222 of the second output stage 220B.

[00239] However, different from the output control circuit 230A, the output control circuit 230B also selectively couples the V_B input, V_BJN , to either the third switch control output, V_Sw2B, or the fourth switch control output, V_SW-I B, based upon the minimum headroom voltage, VHEADROOM, the saved charge voltage, V_AB_, and the power amplifier supply voltage, V_Cc- For example, when the power amplifier supply voltage, V_Cc, is greater than the saved charge voltage, V_AB, plus the minimum headroom voltage, VHEADROOM, the output control circuit 230B couples the V_B input, V_BJN , to the third switch control output, V_Sw2B, and sets the fourth switch control output, V_SWI B, to disable the second switching element , SW1 _B, 216. As an example, the output control circuit 230B may pull down the fourth switch control output, V_SW-I B, to ground. As a result, the second amplifier output voltage, V_B, is coupled to the gate 224G of the second switching element, SW2_B, 224 of the second output stage 220B.

[00240] However, when the power amplifier supply voltage, V_Cc, is less than or equal to the saved charge voltage, V_AB> plus the minimum headroom voltage, VHEADROOM, the output control circuit 230B couples the fourth switch control output, V_SWI B, to the V_B input, V_BJN , and sets the third switch control output, Vsw2B, to disable the second switching element, SW 2_B, 224. As an example, the output control circuit 230B may pull down the third switch control output, Vsw2B, to ground. As a result, the second amplifier output voltage, V_B, is coupled to the gate 216G of the second switching element, SW1 _B, 216 of the first output stage 210C.

[00241 ] While the embodiments of the parallel amplifier 35A, the

rechargeable parallel amplifier 35B, and the rechargeable parallel amplifier 35C of Figures 12A, Figure 12B, and Figure 12C, respectively, depict that the source 214S of the first switching element, SW1 _A, 214 of the first output stage 210 and 12C are coupled to supply input 24 (V_BAT), this is by way of illustration and non- limiting. In some embodiments, the supply voltage provided to the parallel amplifier 35A, rechargeable parallel amplifier 35B, and the rechargeable parallel amplifier 35C of Figures 12A, Figure 12B, and Figure 12C, may be provided by a separate power supply not depicted herein. The separate power supply may provide other voltage levels to power or bias the respective parallel amplifier 36A, rechargeable parallel amplifier 35B, and the rechargeable parallel amplifier 35C. As a non-limiting example, the separate power supply may provide a parallel amplifier supply voltage substantially equal to 2 x V_BAT- Accordingly, in these example embodiments of the parallel amplifier 35A, the rechargeable parallel amplifier 35B, and the rechargeable parallel amplifier 35C, source 214S of the first switching element, SW1 _A, 214 of the first output stage 210 may be coupled to the parallel amplifier supply voltage substantially equal to 2 x V_BAT- [00242] As an example, discussed relative to Figures 18A-D, Figure 12D depicts one embodiment of a parallel amplifier 35D, similar to the parallel amplifier 35A, that is configured to use a parallel amplifier supply voltage,

VSUPPLY_PARA_AMP- In some embodiments, the parallel amplifier supply voltage, VSUPPLY_PARA_AMP, may be configured to come from various power supply voltage generation circuits depending upon the needs of the power amplifier 22. As depicted in Figures 18A-D, the parallel amplifier supply voltage, V_SUPPLY_PARA_AMP, may be provided by a μθ charge pump circuit 262 or by the multi-level charge pump circuit 258 of multi-level charge pump buck converter 12C. In addition, as discussed below, in some embodiments of the μθ charge pump circuit 262, the μθ charge pump circuit 262 generates a μθ charge pump output voltage, ν_μο_ουτ, that may be configured to provide various voltage levels dependent upon the mode of operation of the μθ charge pump circuit 262.

[00243] As depicted in Figure 12D, unlike the parallel amplifier 35A of Figure 12A, the parallel amplifier 35D may be configured to use the parallel amplifier supply voltage, V_SUPPLY_PARA_AMP, instead of the supply input 24, V_BAT, provided by the battery 20. The parallel amplifier supply voltage,

VSUPPLY_PARA_AMP, may be a discrete ratio of the supply input 24, (V_BAT) provided by battery 20. In other embodiments, however, the voltage level provided by the parallel amplifier supply voltage, V_SUPPLY_PARA_AMP, may be programmatically selected depending upon the operational conditions of the mobile device or pseudo-envelope follower power management system.

[00244] For example, as depicted in Figure 12D, the source 214S of the first switching element, SW1 _A, 214 may be coupled to the parallel amplifier supply voltage, V_SUPPLY_ PARA_AMP- Although not depicted in Figure 12D, the circuitry associated with the first power amplifier, AMP_A 206 and the second power amplifier AMP_B 208, may also be supplied by the parallel amplifier supply voltage, VSUPPLY_PARA_AMP- [00245] As another example, Figure 12E depicts an embodiment of the rechargeable parallel amplifier 35E that is similar to the rechargeable parallel amplifier 35B depicted in Figure 12B. Unlike the rechargeable parallel amplifier 35B, the parallel amplifier 35E is configured to use the parallel amplifier supply voltage, V_SUPPLY_PARA_AMP, instead of the supply input 24, (V_BAT) provided by the battery 20.

[00246] Accordingly, unlike the rechargeable parallel amplifier 35B, the rechargeable parallel amplifier 35E is configured such that the source 214S of the first switching element, SW1 _A, 214, is coupled to the parallel amplifier supply voltage, V_SUPPLY_PARA_AMP- Similar to the parallel amplifier 35D of Figure 12D, the rechargeable parallel amplifier 35E may also be reconfigured to use the parallel amplifier supply voltage, V_SUPPLY_PARA_AMP, as the supply voltage of the first amplifer AMP_A, 206, the second amplifier, AMP_B, 208, and the output control circuit 230A.

Figure 12F depicts another embodiment of the rechargeable parallel amplifier 12C as a rechargeable parallel amplifier 12F. Similar to the rechargeable parallel amplifier 12D, depicted in Figure 12D, and the rechargeable parallel amplifier 12E, depicted in Figure 12E, the rechargeable parallel amplifier 12F is configured to use the parallel amplifier supply voltage, V_SUPPLY_PARA_AMP, instead of the supply input 24, (V_BAT), supplied by the battery 20. Also similar to the parallel amplifier 12D and the rechargeable parallel amplifier 12E, rechargeable parallel amplifier 12F is configured such that the source 214S of the first switching element, SW1 _A, 214, coupled to the parallel amplifier supply voltage,

VSUPPLY_PARA_AMP, instead of the supply input 24, (V_BAT)- Also similar to the rechargeable parallel amplifier 35E, depicted in Figure 12E, the first amplifier, AM PA, 206, the second amplifier, AMP_B, 208, and the output control circuit 230B may also be further configured to use the parallel supply voltage,

VSUPPLY_PARA_AMP, as a supply source instead of the supply input 24.

[00247] Returning to Figure 2A, the open loop assist circuit 39 will now be discussed. As discussed above, the parallel amplifier circuit output current, IPAWA_OUT, may be a combination of the parallel amplifier output current IPARA_AMP, and the open loop assist circuit, I ASSIST- The open loop assist circuit 39 may be used to reduce the amount of current that the parallel amplifier 35 of the parallel amplifier circuit 32 may need to source and sink in order to regulate the power amplifier supply voltage, Vcc. In particular, the parallel amplifier 35 may sink excess power inductor current, I SW_OUT, that can generate a large voltage ripple on the power amplifier supply voltage, V_Cc- The large voltage ripple on the power amplifier supply voltage, V_Cc, can be due to the interaction of the power inductor current, ISW_OUT, with the non-zero impedance of parallel amplifier 35 over frequency in the pass band of the pseudo-envelope follower power management system. The open loop assist current, SSIST, provided by the open loop assist circuit 39 can be configured to reduce the parallel amplifier output current, l pARA_AMP, sourced or sunk by the parallel amplifier 35, which may reduce the ripple voltage on the power amplifier supply voltage, Vcc, because the non-zero output impedance of the parallel amplifier 35 is convoluted with less current..

[00248] One embodiment of the open loop assist circuit 39 may be configured to receive an estimated power inductor inductance parameter, LEST, and a minimum power amplifier turn on voltage parameter, V₀FFSET_PA, an estimated bypass capacitor capacitance parameter, C_BYPASS_EST, and an estimated power amplifier transconductance parameter, K_I₀UT_EST- [00249] The estimated power inductor inductance parameter, LEST, may be either the measured or estimated inductance of the power inductor 16 between a specific range of frequencies. For example, the estimated power inductor inductance parameter, LEST, may be either the measured or estimated inductance of the power inductor 16 between approximately 10MHz and 30MHz. The minimum power amplifier turn on voltage parameter, V₀FFSET_PA, may be either the measured or estimated value of the minimum supply voltage at which the linear RF power amplifier 22 will begin to operate. The estimated bypass capacitor capacitance parameter, CBYPASS_EST, may be either the measured or estimate capacitance of the bypass capacitor, C_BYPASS,19 measured between a specific range of frequencies. For example, the estimated bypass capacitor capacitance parameter, CBYPASS_EST, may be either the measured or estimated capacitance of the bypass capacitor, CBYPASS_J19 between approximately 10MHz and 30MHz. The estimated power amplifier transconductance parameter,

JOUT_EST, may be either the measured or estimated transconductance of the linear RF power amplifier 22. Transconductance of the linear RF power amplifier 22 may be 1 /RLOAD, where RLOAD, is the estimated resistive load of the linear RF power amplifier 22. The estimated power amplifier transconductance parameter, JOUT_EST, may be either the measured or estimated transconductance of the linear RF power amplifier 22 between a specific range of frequencies. For example, the estimated power amplifier transconductance parameter, K_I₀UT_EST, may be either the measured or estimated transconductance of the linear RF power amplifier 22 between approximately 10MHz and 30MHz.

[00250] The estimated power inductor inductance paramenter, LEST, the minimum power amplifier turn on voltage parameter, V₀FFSET_PA, the estimated bypass capacitor capacitance parameter, C_BYPASS_EST, and the estimated power amplifier transconductance parameter, K_I₀UT_EST may be provided by the controller 50 through the control bus 44, as depicted in Figures 1 A and 1 B.

Typically, values of the estimated power inductor inductance parameter, LEST, minimum power amplifier turn on the voltage parameter, V₀FFSET_PA, the estimated bypass capacitor capacitance parameter, C_BYPASS_EST, and the estimated power amplifier transconductance parameter, K_I₀UT_EST, are obtained at calibration time of the pseudo-envelope follower system. [00251 ] In addition, the open loop assist circuit 39 may be configured to receive the feed forward control signal, VSWITCHER, 38 from the multi-level charge pump buck converter 12. As discussed above, the feed forward control signal, VSWITCHER, 38 may be configured to provide either the scaled version of the switch voltage, V_SW_SCALED, 38A or the indication of the switching voltage output, VSW_EST, 38B. The open loop assist circuit 39 may also be configured to receive the VRAMP signal, from the first control input 34. The open loop assist circuit 39 may also receive a V_RAMP signal from the first control input 34.

[00252] Figure 9A depicts a more detailed block diagram of an embodiment of the open loop assist circuit 39 of Figure 2A, which is depicted as an open loop circuit 39A. The open loop circuit 39A will be described with continuing reference to Figures 1 A and 2A. The open loop circuit 39A includes an output current estimator 240, a bypass capacitor current estimator 242, a power inductor current estimator 244A, a summing circuit 246, and a controlled current source 248. The output current estimator 240 receives the VRAMP signal, the estimated power amplifier transconductance parameter, K_l OUT ESTJ and the minimum power amplifier turn on voltage parameter, V₀FFSET_PA- The output current estimator 240 generates an output current estimate, IOUT_EST, based upon the VRAMP signal, the estimated power amplifier transconductance parameter,

KJOUT_EST, and the minimum power amplifier turn on voltage parameter,

VOFFSET_PA- The output current estimate, IOUT_EST, is an estimate of the output current, Ιουτ, provided to the linear RF power amplifier 22.

[00253] In one embodiment, the output current estimator 240 calculates the difference between the V_RAMP signal and the minimum power amplifier turn on voltage parameter, V₀FFSET_PA, by subtracting the minimum power amplifier turn on voltage parameter, V_OFFSET_PA, from the VRAMP signal (VRAMP - V_OFFSET_PA). Thereafter, the difference between the V_RAMP signal and the minimum power amplifier turn on voltage parameter, V₀FFSET_PA, is scaled by the estimated power amplifier transconductance parameter, K_l OUT_EST_J to generate the output current estimate, IOUT_EST, where IOUT_EST = K_I₀UT_EST^* (VRAMP - V₀FFSET_PA). Typical circuitry may include an operational amplifier to perform (V_RAMP - V_QFFSET_PA) and the voltage difference is applied to a transconductance amplifier, which the transconductance amplifier gain, Gm, is programmable and equal to K_I₀UT_EST- [00254] The bypass capacitor current estimator 242 receives the V_RAMP signal and the estimated bypass capacitor capacitance parameter, C_BYPASS_EST- The bypass capacitor current estimator 242 generates a bypass capacitor current estimate, IBYPASS_EST, based upon the V_RAMP signal and the estimated bypass capacitor capacitance parameter, C_BYPASS_EST- The bypass capacitor current estimate, IBYPASS_EST, is an estimate of the bypass capacitor current, IBYPASS_CAP, delivered by the bypass capacitor 1 9.

[00255] In one embodiment, the V_RAMP signal is differentiated to provide a VRAMP rate of change signal, d(V_RAMp)/dT, which serves as an estimate of the rate of change of the voltage across the bypass capacitor, CBYPASS, 9. The V_RAMP rate of change signal, d(V_RAMp)/dT, may be an estimate of the rate of change of the V_RAMP signal over time. In some embodiments, the V_RAMP rate of change signal, d(V_RAMp)/dT, is generated by a high pass filter having a desired time constant. A simple high-pass filter followed by a gain provide a frequency response below its corner frequency that have a +6dB/octave slope thus equivalent to "s laplace transform" and thus creating a differentiator function below the corner frequency. The high-pass filter is typically made of series capacitor and a shunt resistor. In some embodiments, the time constant of the high pass filter may be between the range of 8 nanoseconds and 1 6

nanoseconds.

[00256] The power inductor current estimator 244A receives the V_RAMp signal, the feed forward control signal, VSWITCHER, 38, and the estimated power inductor inductance parameter, LEST- The power inductor current estimator 244A generates a power inductor current estimate, I SW_OUT_EST_J based upon the V_RAMP signal, the feed forward control signal, VSWITCHER, 38, and the estimated power inductor inductance parameter, L_EST- The power inductor current estimate, ISW_OUT_EST, is an estimate of the power inductor current, I SW_OUT_J delivered by the power inductor 1 6. [00257] In one embodiment of the power inductor current estimator 244A, the power inductor current estimator 244A subtracts the V_RAMP signal from the feed forward control signal, VSWITCHER, 38, to generate a difference voltage VDIFFERENCE- The power inductor current estimator 244A may include an integrator circuit (not shown) that integrates the difference voltage VDIFFERENCE to generate an accumulated difference signal. The power inductor current estimator 244A then scales an accumulated difference signal with a factor of 1/L_EST, to generate the power inductor current estimate, ISW_OUT_EST- The bandwidth of the integrator circuit used to integrate the difference voltage VDIFFERENCE may be between 5 MHz and 45 MHz. In some embodiments, the integrator slope may be programmable. For example, the controller 50 may adjust the gain of the transistors of the integrator circuit (not shown) of the power inductor current estimator 244A in order to adjust the integrator slope. Also, it is possible to use a low-pass filter followed by a gain which above the corner frequency the slope versus frequency is -6dB/octave similar to "1 /s Laplace transform" thus acting as an integrator in the frequencies above the corner frequency. The corner frequency can be set below 5MHz and is made programmable.

[00258] In another embodiment of the power inductor current estimator 244A the power inductor current estimator 244A divides the accumulated difference signal by the estimated power inductor inductance parameter, L_EST, to generate the power inductor current estimate, ISW_OUT_EST- [00259] In still another embodiment of the power inductor current estimator 244A, the difference voltage, VDIFFERENCE, is scaled by the factor of 1 /L_EST, or divided by the estimated power inductor inductance parameter, L_EST, to generate a scaled difference signal, S DIFFERENCE_SCALED, (not shown) prior to integration. The power inductor current estimator 244A then integrates a scaled difference signal, S_DIFFERENCE_SCALED, (not shown) to generate the power inductor current estimate, ISW_OUT_EST- In yet another embodiment of the power inductor current estimator 244A, the power inductor current estimator 244A scales the V_RAMP signal and the feed forward control signal, VSWITCHER, 38 by the factor of 1 /LEST, or divides the V_RAMP signal and the feed forward control signal, VSWITCHER, 38 by the estimated power inductor inductance parameter, L_EST, prior to calculating the scaled difference signal, SDIFFERENCE_SCALED, (not shown). Thereafter, the scaled difference signal, S_DIFFERENCE__SCALED, is integrated to generate the power inductor current estimate, ISW_OUT_EST- [00260] When the feed forward control signal, VSWITCHER, 38, is configured to provide the switching voltage output, V_SW__EST, 38B to the open loop assist circuit 39, the power inductor current estimate, I_SW__OUT__EST, is generated based upon switching voltage output, V_SW__EST, 38B. When the feed forward control signal, VSWITCHER, 38, is configured to provide the switch voltage, V_SW_SCALED, 38A to the open loop assist circuit 39, the power inductor current estimate, ISW_OUT_EST, is generated based upon the switching voltage output, V_SW_SCALED, 38A.

[00261 ] The summing circuit 246 is configured to receive the output current estimate, IOUT_EST, the bypass capacitor current estimate, IBYPASS_EST, and power inductor current estimate, I _SW__OUT__EST- The summing circuit 246 subtracts the bypass capacitor current estimate, I _BYPASS__EST, and the power inductor current estimate, ISW_OUT_EST, from the output current estimate, IOUT_EST, to generate an estimate of the open loop assist current, I ASSIST_EST- The open loop assist current, IASSIST_EST, is an estimate of the open loop assist current, SSIST, provided by the open loop assist circuit 39A to the amplifier output 32A in order to generate the parallel amplifier circuit output current, IPAWA_OUT, from the parallel amplifier circuit 14.

[00262] The controlled current source 248 is a controlled current source that generates the open loop assist current, _SSIST, based upon the open loop assist current, IASSIST_EST- The open loop assist current can be activated when reduced voltage ripple reduction is required and can be disabled when voltage ripple reduction is not required like when operating at lower power amplifier output power. The open loop assist current can be made of three separate controlled current sources, where each controlled current source is controlled by ISW_OUT_EST, IBYPASS_EST and IOUT_EST , respectively. Also, the SSIST current in phase may be time aligned with the parallel amplifier output current, I _PARA__AMP. For example, when SSIST current is positive, IPARA_AMP may be positive and when the open loop assist current, I_ASSIST, is negative, the parallel amplifier output current, I _PARA__AMP, may also be negative as such there is no wasted currents, where the parallel amplifier output current, I_PARA__AMP, that is sourced is not sunk by the open loop assist circuit 39A.

[00263] Figure 9B depicts another embodiment of the open loop assist circuit 39B. As depicted in Figure 9B, the open loop assist circuit 39B is similar to the open loop assist circuit 39A except that the open loop assist circuit 39B receives the switching voltage output, V_SW__EST, 38B as the feed forward control signal instead of the feed forward control signal, VSWITCHER, 38. Accordingly, the switching voltage output, V_SW__EST, 38B includes a power inductor current estimator 244B instead of the power inductor current estimator 244A. The power inductor current estimator 244B is similar to the power inductor current estimator 244A except the power inductor current estimator 244B only receives the feed forward control signal switching voltage output, V_SW__EST, 38B instead of the feed forward control signal, VSWITCHER, 38.

[00264] As a result, the power inductor current estimate, ISW_OUT_EST, generated by the power inductor current estimator 244B is based upon the switching voltage output, V_SW__EST, 38B. As a result, the power inductor current estimator 244B is functionally like the power inductor current estimator 244A when the feed forward control signal, VSWITCHER, 38 provides the feed forward control signal switching voltage output, V_SW__EST, 38B. Accordingly, the open loop assist circuit 39B operates in a similar manner as the open loop assist circuit 39A when the V_SWITCHER, 38 provides the switching voltage output, V_SW__EST, 38B to the open loop assist circuit 39A.

[00265] Returning to Figure 2B, the parallel amplifier output impedance compensation circuit 37 will now be discussed. The combination of the multilevel charge pump buck converter 12 and the parallel amplifier 35 of the parallel amplifier circuit 32 may not have a flat frequency response across the modulation bandwidth of the power amplifier supply voltage, V_Cc, provided to the linear RF power amplifier 22. In particular, the desired modulation bandwidth of the power amplifier supply voltage, V_Cc, is between 1 .5 to 2.5 times the RF modulation bandwidth of the linear RF power amplifier 22. As an example, the Long Term Evolution LTE 3GPP standard the RF modulation bandwidth may be up to 20MHz. As a result, the desired modulation bandwidth of power amplifier supply voltage, V_Cc, generated by the pseudo-envelope follower power management system 10A may be between 30 MHz to 40MHz. In some embodiments of the pseudo-envelope follower power management system 10A, the desired modulation bandwidth of the power amplifier supply voltage, V_Cc, may be approximately 35MHz. However, at higher frequencies, the output impedance of the parallel amplifier 35 that regulates the power amplifier supply voltage, V_Cc, may become inductive. The output impedance of the parallel amplifier 35 combines with the bypass capacitor capacitance, CBYPASS, of the bypass capacitor 19 to roll off the modulation frequency response of the parallel amplifier 35. The roll off of the modulation frequency response of the parallel amplifier 35 may result in increased ripple voltage in the power amplifier supply voltage, V_Cc, due to the inductor current, ISVV OUT, provided by the power inductor 16. The parallel amplifier output impedance compensation circuit 37 may be configured to pre-compensate the V_RAMP signal in order to provide a compensated V_RAMP signal, V_RAMP_C, to the parallel amplifier 35 in order to flatten the modulation frequency response of the parallel amplifier 35.

[00266] The parallel amplifier output impedance compensation circuit 37 depicted in Figure 2A is configured to receive the V_RAMP signal, an estimated bypass capacitor capacitance parameter, C_BYP_ASS_EST, and a parallel amplifier inductance estimate parameter, L_CORR- The parallel amplifier inductance estimate parameter, L_CORR, may be an estimated inductance of the parallel amplifier 35 between the frequencies 10MHz and 30MHz, which is measured during calibration. The parallel amplifier inductance estimate parameter, L_CORR, may be provided by the controller 50 via the control bus 44 at configuration time.

[00267] Figure 10A depicts one example embodiment of the parallel amplifier output impedance compensation circuit 37 depicted in Figure 2A as a parallel amplifier output impedance compensation circuit 37A. The parallel amplifier output impedance compensation circuit 37A may include a first differentiator circuit 250, a second differentiator 252, a frequency pre-distortion circuit 254, and a summing circuit 256.

[00268] The first differentiator circuit 250 receives the V_RAMP signal and the estimated bypass capacitor capacitance parameter, CBYPASS_EST- Similar to the bypass capacitor current estimator 242 of Figures 9A and 9B, the first

differentiator circuit 250 generates a bypass capacitor current estimate, I BYPASS- _EST, based upon the Vramp signal and the bypass capacitor capacitance parameter, CBYPASS_EST- The bypass capacitor current estimate, IBYPASS_EST, is an estimate of the bypass capacitor current, I BYPASS_CAP_J delivered by the bypass capacitor, CBYPASS, 9. In some embodiments of the parallel amplifier output impedance compensation circuit 37A, the parallel amplifier output impedance compensation circuit 37A uses the bypass capacitor current estimate, IBYPASS_EST, provided by the bypass capacitor current estimator 242 and the first differentiator circuit 250 is omitted. In other embodiments of the parallel amplifier output impedance compensation circuit 37A, the time constant of the first differentiator circuit 250 may be different than the time constant of bypass capacitor current estimator 242 of the open loop assist circuit 39.

[00269] Similar to the bypass capacitor current estimator 242, in one embodiment of the first differentiator circuit 250, the VRAMP signal is differentiated to provide a VRAMP rate of change signal, d(V_RAMp)/dT, which serves as an estimate of the rate of change of the voltage across the bypass capacitor,

CBYPASS, 9. The V_RAMP rate of change signal, d(V_RAMp)/dT, may be an estimate of the rate of change of the V_RAMP signal over time. In some embodiments, the

VRAMP rate of change signal, d(V_RAMp)/dT, is generated by a high pass filter (not shown) having a desired time constant. As an example, a simple high-pass filter followed by a gain stage may provide a frequency response below its corner frequency that has a +6dB/octave slope, thus equivalent to the "s laplace transform" and thus creating a differentiator function below the corner frequency. The high-pass filter (not shown) is typically made of a series capacitor and a shunt resistor. In some embodiments, the time constant of the high pass filter may be between the range of 8 nanoseconds and 1 6 nanoseconds.

[00270] The bypass capacitor current estimate, I BYPASS_EST, and the scaled parallel amplifier output current estimate, I PARA_AMP_SENSE, are combined to create a dynamic current, I DYNAMIC, which is provided to the second differentiator circuit 252. The dynamic current, I DYNAMIC, represents the dynamic portion of the power inductor current, I SW_OUT, delivered by the power inductor 1 6. The second differentiator 252 is to replicate the parallel amplifier output impedance frequency response, which exhibits an output impedance that increases at +6dB/octave, like an inductor , at the frequency range where the switcher current is operating, up to a resonance frequency equal to 1 /(2*pi*sqrt(L_CoRR * C_bypass))- [00271 ] The second differentiator circuit 252 is configured to receive the dynamic current, I DYNAMIC, and the parallel amplifier inductance estimate parameter, LCORR- [00272] The second differentiator circuit 252 differentiates the dynamic current, I DYNAMIC, to provide a dynamic current rate of change signal,

d( l DYNAMic)/dT. The dynamic current rate of change signal, d( l DYNAMic)/dT, estimates change of the dynamic current, I DYNAMIC, with respect to time. In some embodiments, the dynamic current rate of change signal, d(l_DYNAMic)/dT, is generated by a low pass (not shown) having a desired time constant. The time constants of the second differentiator circuit 252 may be configured to optimize the modulation bandwidth of the parallel amplifier 35. The second differentiator can be made from a high-pass filter (not shown) followed by a gain to provide a frequency response below its corner frequency that has a +6dB/octave slope thus equivalent to "s Laplace transform" and thus creating a differentiator function below the corner frequency. The high-pass filter is typically made of a series capacitor and a shunt resistor. The time constant of the high-pass filter may be between 8 nanoseconds and 16 nanoseconds. The second differentiator circuit 252 scales the dynamic current rate of change signal, d( l DYNAMic)/dT, by the parallel amplifier inductance estimate parameter, LCORR, to generate a power amplifier supply ripple voltage estimate, VRI_PPLE, at the negative input of the summer circuit 256. The power amplifier supply ripple voltage estimate is an estimate of the ripple voltage component of the power amplifier supply voltage, Vcc_, at the power amplifier supply node 28.

[00273] The frequency pre-distortion circuit 254 may be configured to receive the VRAMP signal and output a peeked VRAMP signal, VRAMP_PEEK- The frequency pre-distortion circuit 254 may be a programmable peeking filter that may be configured to compensate for the roll off of the modulation frequency response of the parallel amplifier 35. The frequency pre-distortion circuit 254 may include a frequency equalizer circuit that includes a programmable pole time constant, Tau_Pole, and a programmable zero time constant, Tau_Zero. The frequency pre-distortion circuit Laplace transfer function, V_RAMPC / VRAMP, may be approximately equal to [1 +Tau_Zero^*s] / [1 +Tau_Pole^*s]. The programmable pole time constant, Tau_Pole, and the programmable zero time constant, Tau_Zero, may be adjusted to increase the frequency response of the frequency pre-distortion circuit 254, V_RAMPC / V_RAMP, in order to flatten the overall modulation frequency response of the pseudo-envelope follower power management system 10A. In some embodiments of the frequency pre-distortion circuit 254, the programmable pole time constant, Tau_Pole, is configured to about .4

microseconds, (1 /2.5MHz). The programmable zero time constant, Tau_Zero, may be configured to be about .192 microseconds, (1 /5.8MHz). As a result, the pseudo-envelope follower power management system transfer function, V_Cc / V- RAMPs, may be flattened up to about 35MHz.

[00274] Figure 13 depicts an embodiment of a pseudo-envelope follower power management system 10G including a buck converter 13G and a parallel amplifier circuit 14G having an open loop assist circuit 39 and a parallel amplifier circuit 32. In some alternative embodiments of the pseudo-envelope follower power management system of Figure 13, the parallel amplifier 35 may be a rechargeable parallel amplifier. As an example, the rechargeable parallel amplifier 35 may be a rechargeable parallel amplifier similar to the embodiments of the rechargeable parallel amplifier depicted in Figures 12B-C and Figures 12E- F. [00275] Figure 14 depicts another embodiment of a pseudo-envelope follower power management system 10H including a multi-level charge pump buck converter 12H and a parallel amplifier circuit 14H having an open loop assist circuit 39 and a parallel amplifier circuit 32. In some alternative

embodiments of the pseudo-envelope follower power management system of Figure 14, the parallel amplifier 35 may be a rechargeable parallel amplifier similar to the embodiments of the rechargeable parallel amplifier depicted in Figures 12B-C and Figures 12E-F.

[00276] Figure 15 depicts another embodiment of a pseudo-envelope follower power management system 101 including a multi-level charge pump buck converter 121 and a parallel amplifier circuit 141 having a parallel amplifier circuit 32 and a VOFFSET loop circuit 41 E. In some embodiments, VOFFSET loop circuit 41 E may be similar to either the VOFFSET loop circuit 41 A. as depicted in Figure 18A, or the VOFFSET loop circuit 41 B, as depicted in Figure 18B.

Accordingly, although not shown in Figure 15, the VOFFSET loop circuit 41 E may be coupled to a controller 50 (not shown), which may be used to configure the VOFFSET loop circuit 41 E. In addition, in some alternative embodiments of the pseudo-envelope follower power management system 10E, depicted in Figure 15, the parallel amplifier 35 may be a rechargeable parallel amplifier similar to the embodiments of the rechargeable parallel amplifier depicted in Figures 12B-C and Figures 12E-F.

[00277] Figure 16 depicts another embodiment of a pseudo-envelope follower power management system 10J including a multi-level charge pump buck converter 12J and a parallel amplifier circuit 32 having a parallel amplifier 32, a VOFFSET Loop Circuit 41 F, an open loop assist circuit 39 and a parallel amplifier output impedance compensation circuit 37. In some embodiments, the VOFFSET loop circuit 41 F may be similar to either the VOFFSET loop circuit 41 A, as depicted in Figure 18A, or the VOFFSET loop circuit 41 B, as depicted in Figure 18B. Accordingly, although not shown in Figure 16, the VOFFSET loop circuit 41 F may be coupled to a controller 50 (not shown), which may be used to configure the VOFFSET loop circuit 41 F. In addition, in some alternative embodiments of the pseudo-envelope follower power management system 1 0J, depicted in Figure 1 6, the parallel amplifier 35 may be a rechargeable parallel amplifier similar to the embodiments of the rechargeable parallel amplifier depicted in Figures 1 2B-C and Figures 1 2E-F.

[00278] Figure 1 7A depicts another embodiment of a pseudo-envelope follower power management system 1 0K including a buck converter 1 3K and a parallel amplifier circuit 32 having a rechargeable parallel amplifier 35B. The parallel amplifier output current, I PARA_AMP, may be the sole contributor to the parallel amplifier circuit output current I PAWA_OUT, of the parallel amplifier circuit 14K. In addition, because the parallel amplifier circuit 14K does not have an open loop assist circuit, the parallel amplifier circuit output current, I PAWA_OUT_EST, 40 is equal to the scaled parallel amplifier output current estimate, I PARA_AMP_SENSE, current provided by the parallel amplifier sense circuit 36. Also, in some alternative embodiments of the pseudo-envelope follower power management system 1 0G, depicted in Figure 1 7A, the parallel amplifier 35B may be a rechargeable parallel amplifier similar to the embodiments of the rechargeable parallel amplifier depicted in Figure 12E.

[00279] Figure 1 7B depicts another embodiment of a pseudo-envelope follower power management system 1 0L including a multi-level charge pump buck converter 1 2L and a parallel amplifier circuit 32 having a parallel amplifier circuit 32. The parallel amplifier output current, I PARA_AMP, may be the sole contributor to the parallel amplifier circuit output current I PAWA_OUT, of the parallel amplifier circuit 14L. In addition, because the parallel amplifier circuit 14L does not have an open loop assist circuit, the parallel amplifier circuit output current, I PAWA_OUT_EST, 40 may be equal to the scaled parallel amplifier output current estimate, I PARA_AMP_SENSE, current provided by the parallel amplifier sense circuit 36. In addition, in some alternative embodiments of the pseudo-envelope follower power management system 1 0L, depicted in Figure 1 7B, the parallel amplifier 35C may be a rechargeable parallel amplifier similar to the

embodiments of the rechargeable parallel amplifier depicted in Figure 1 2E-F. [00280] Figure 18B depicts another embodiment of the pseudo-envelope follower power management system 10E, which is similar to the pseudo- envelope follower power management systems 10A and 10B, as depicted in Figures 1 A and 1 B. The pseudo-envelope follower power management system 10E includes a multi-level charge pump buck converter 12C, a parallel amplifier circuit 14D, a controller 50, a clock management circuit 260, a μθ charge pump circuit 262, a battery level sense circuit 264, and a parallel amplifier power source selection circuit 272 operably configured to generate a parallel amplifier supply voltage, V_Cc, on the bypass capacitor (CBYPASS) 19.

[00281 ] Similar to the embodiments of the pseudo-envelope follower power management system 10A-10B of Figures 2A-2B, the pseudo-envelope follower power management system 10E may include a multi-level charge pump buck converter 12C that is similar to the multi-level charge pump buck converters 12A- B depicted in Figures 2A-B. However, unlike the multi-level charge pump buck converters 12A-B, the multi-level charge pump buck converter 12C further includes a multi-level charge pump circuit 258 configured to generate an internal charge pump node parallel amplifier supply 294. In some embodiments of the multi-level charge pump buck converter 12C, the multi-level charge pump circuit 258 may provide 1 .5 x V_BAT as the internal charge pump node parallel amplifer supply 294. In other embodiments of the multi-level charge pump buck converter 12C, the multi-level charge pump circuit 258, the output voltage level of the internal charge pump node parallel amplifier supply 294 may vary between 1 .5 x VBAT and 2 x V_BAT depending upon the operational mode of the multi-level charge pump circuit 258. Example embodiments of the multi-level charge pump circuit 258 are described relative to Figures 7A-B. Also similar to the multi-level charge pump buck converters 12A-B of Figures 2A-B, the multi-level charge pump buck converter 12C may include a switching voltage output 26.

[00282] Similar to the embodiments of the pseudo-envelope follower power management system 10A-10B of Figures 2A-2B, the switching voltage output 26 of the multi-level charge pump buck converter 12C may be coupled to a power inductor 16. The power inductor 16 is coupled to the bypass capacitor (CBYPASS) 19 to form a low pass filter for the multi-level charge pump buck converter 12C. In addition, similar to the parallel amplifier circuits 14A-14B of Figures 2A-2B, the parallel amplifier circuit 14D may include a parallel amplifier output 32A that is coupled to the power amplifier supply voltage, V_Cc_, via the coupling circuit 18. In the case where the coupling circuit 18 provides AC (alternating current) coupling between the parallel amplifier output 32A of the parallel amplifier circuit 14D and the power amplifier supply voltage, V_Cc, an offset voltage, VOFFSET, may be developed across the coupling circuit 18. Also, the parallel amplifier circuit 14D may include a parallel amplifier circuit 32 operably coupled to the parallel amplifier output 32A.

[00283] However, unlike the parallel amplifier circuit 14A-B of Figures 2A- 2B, the parallel amplifier circuit 14D may be configured to power the parallel amplifier circuit 32 with a parallel amplifier supply voltage, V_SUPPLY_PARA_AMP, instead of the supply input 24, (V_BAT)- The parallel amplifier supply voltage, VSUPPLY_PARA_AMP, may be provided by the parallel amplifier power source selection circuit 272. In one example embodiment of the parallel amplifier circuit 14D, the parallel amplifier 35 may be configured similar to the parallel amplifier 32D, which is depicted in Figure 12D. Alternatively, in other embodiments, the parallel amplifier 35 may be a rechargeable parallel amplifier similar to the rechargeable parallel amplifiers 35E-F, which are respectively depicted in Figures 12E-F.

[00284] The parallel amplifier power source selection circuit 272 may include a first input coupled to the μC charge pump output of the μC charge pump circuit 262 and a second input coupled to the internal charge pump node parallel amplifier supply 294 of the multi-level charge pump circuit 258. The parallel amplifier power source selection circuit 272 may also be coupled to the controller 50 via a source selection control signal 296. The parallel amplifier power source selection circuit 272 may include an output configured to provide the parallel amplifier supply voltage, V_SUPPLY_PARA_AMP, to the parallel amplifier circuit 14D based upon the state of the source selection control signal 296. In addition, the parallel amplifier power source selection circuit 272 may coupled to the controller 50 via the source selection control signal 296. Via the source selection control signal 296, the controller 50 may configure the parallel amplifier power source selection circuit 272 to select either the internal charge pump node parallel amplifier supply 294 or the μθ charge pump output in order to provide the parallel amplifier supply voltage, V_SUPPLY_PARA_AMP, to the parallel amplifier circuit 14D. In some alternative embodiments of the pseudo-envelope follower power management system 10E, the parallel amplifier power source selection circuit 272 may be eliminated. In this case, either the internal charge pump node parallel amplifier supply 294 or the μθ charge pump output of the μθ charge pump circuit 262 may be directly coupled to the parallel amplifier circuit 14D in order to provide the parallel amplifier supply voltage, V_SUPPLY_PARA_AMP. For example, some embodiments of the multi-level charge pump buck converter 12C may not provide an internal charge pump node parallel amplifier supply 294 as an output. In this case, the μθ charge pump output of the μθ charge pump circuit 262 is directly coupled to the parallel amplifier circuit 14C to provide the parallel amplifier supply voltage V_SUPPLY_PARA_AMP, as the operational voltage for the parallel amplifier 35 and associated circuitry.

[00285] In still another alternative arrangement (not show), in some embodiments of the pseudo-envelope follower power management system 10E, the parallel amplifier power source selection circuit 272 is eliminated. In this case, the μθ charge pump output of the μθ charge pump circuit 262 and the internal charge pump node parallel amplifier supply 294 are coupled together to form a parallel amplifier supply node that provides the parallel amplifier supply voltage, V_SUPPLY_PARA_AMP- The desired source for providing the parallel amplifier supply voltage, V_SUPPLY_ _PARA_AMP_J is then managed by enabling and disabling the μθ charge pump circuit 262 and controlling the switch state of the ninth switch 1 19 of the multi-level charge pump 258A-B of Figures 7B-C. As an example, when the μθ charge pump circuit 262 is disable by setting the μθ charge pump, μΒΒρΑτιο, to OFF, the μθ charge pump output floats. In a similar fashion, setting the switch state of the ninth switch 1 19 of the multi-level charge pump 258A-B of Figures 7B-C to be open operably disconnects the internal circuitry of the multi- level charge pump 258A-B of Figures 7B-C from the parallel amplifier supply node.

[00286] The μθ charge pump circuit 262 includes a supply input coupled to supply input 24, (V_BAT), provided by the battery and a μθ charge pump output configured to provide a μθ charge pump output voltage, ν_μ0_ουτ- In addition, the μθ charge pump circuit 262 may be configured to receive a μθ charge pump clock 276 from the clock management circuit 260. The μθ charge pump clock 276 may be used to govern the operation of the μθ charge pump circuit 262. The μθ charge pump circuit 262 is also coupled via a μθ charge pump control bus 278 to the controller 50. As described below relative to Figures 1 9A-B, some embodiments of the μθ charge pump circuit 262 may be configured to boost the supply input 24, (V_BAT), provided by the battery to generate a μθ charge pump output voltage, V _μο_ουτ, that is greater than the supply input 24, (V_BAT)- Other embodiments of the μθ charge pump circuit 262 be may be configured to buck the supply input 24, (V_BAT) to generate a μθ charge pump output voltage, ν_μο_ουτ, that is less than the supply input 24, (V_BAT)- The controller 50 may use the μθ charge pump control bus 278 to configure the μθ charge pump circuit 262 to operate in various operational modes in order to generate specific voltage levels at the μθ charge pump output. For example, the μθ charge pump circuit 262 may be configured to generate a μθ charge pump output voltage, ν_μ0_ουτ, that provides various voltage levels dependent upon the mode of operation of theiC charge pump circuit 262. This permits the multi-level charge pump buck converter 1 2C to provide a desired voltage level as the μθ charge pump output voltage, ν_μ0_ουτ, and dependent upon the need of the parallel amplifier 35 on the parallel amplifier circuit 14D with different voltage output levels dependent upon the needs of the pseudo-envelope follower power management system 1 0C.

[00287] The clock management circuit 260, depicted in Figure 1 8B, may include a reference clock 1 39, a divider circuit 266, a clock selection circuit 268, and an oscillator 270. The clock management circuit 260 may be coupled to controller 50 via various control signals and/or buses. Based upon control inputs received from the controller 50, the clock management circuit 260 may be configured generate a μθ charge pump clock 276, which is provided to the μθ charge pump circuit 262. The controller 50 may configure the clock management circuit 260 to generate the μθ charge pump clock 276 based upon a variety of clock sources.

[00288] The reference clock 139 may be operably configured to provide a clock reference signal 139A to the FLL circuit 54 of the multi-level charge pump buck converter 12C. The FLL circuit 54 may be configured to operate with the reference clock 139 similar to the operational description of the FLL circuit 54A of Figure 3A or the FLL circuit 54A of Figure 3B. In each case, the reference clock 139 may be configured to provide a clock reference signal 139A to the FLL circuit 54A or the FLL circuit 54B as depicted in Figures 3A and 3B. In addition to governing various timing aspects regarding operation of the multi-level charge pump buck converter 12C, similar to the FLL circuits 54A of Figures 3A, some embodiments of the FLL circuit 54 may be configured to provide a threshold scalar 137A (shown in Figure 3A) signal to adjust the operating frequency of the mulit-level charge pump buck converter 12C. Alternatively, other embodiments of the FLL circuit 54, similar to the the FLL circuits 54B of Figures 3A, may be configured to provide a threshold scalar' 137B (shown in Figure 3B) signal to adjust the operating frequency of the multi-level charge pump buck converter 12C.

[00289] In addition, as depicted in Figure 18B, the FLL circuit 54 may be further configured to provide an FLL system clock 280 to the switcher control circuit 259 and the divider circuit 266. The FLL system clock 280 may be synchronized or based upon the operating frequency of the multi-level charge pump buck converter 12C, as described above. As a result, in some

embodiments of the pseudo-envelope follower power management system 10E, the FLL circuit 54 provides an FLL system clock 280 that is synchronized to the switching of the multi-level charge pump buck converter 12C.

[00290] The divider circuit 266 may be configured to receive a clock divider control signal 284 from the controller 50. Based upon the clock divider control signal 284 received from the controller 50, the divider circuit 266 may divide the FLL generated clock to provide a divided FLL clock 282 to the clock selection circuit 268. In addition, the clock selection circuit 268 may be configured to receive the reference clock 139A from the reference clock 139 and an oscillator reference clock 288 from the oscillator 270. Alternative embodiments of the multi-level charge pump buck converter 12C may not include an FLL circuit 54 or the FLL circuit 54 may not be configured to provide a FLL system clock 280 to the clock management system 260.

[00291] The oscillator 270 may be operably coupled to the controller 50 via an oscillator control signal 286. The controller 50 may be configured to modify the output frequency of the oscillator 270 via the oscillator control signal 286. The controller 50 may be further configured to disable or enable the oscillator 270 in order to reduce noise generated by the clock management circuit 260. In other embodiments of the clock management circuit 260, the oscillator 270 may be a fixed oscillator.

[00292] Accordingly, the controller 50 may configure the clock selection circuit 268 to provide one of the divided FLL clock 282, the reference clock 139A, or the oscillator reference clock 288 to the μC charge pump clock 276. As discussed below relative to Figures 19A-B, example embodiments of the μC charge pump circuit 262 may use the μC charge clock 276 to govern the timing between phases of operation of the μC charge pump circuit 262.

[00293] In some embodiments of the pseudo-envelope follower power management system 10C of Figure 18A, the controller 50 advantageously configures the clock selection circuit 268 to provide the divided FLL Clock 282 as the μC charge clock 276. As a result, the switching operations of the μC charge pump circuit 262 may be substantially synchronous to the switching operations of the multi-level charge pump buck converter 12C. In some embodiments of the pseudo-envelope follower power management system 10C, the synchronicity of operations between μθ charge pump circuit 262 and the multi-level charge pump buck converter 12C may improve or reduce the noise performance provided at the power amplifier supply voltage, V_Cc- Alternatively, the controller 50 may configure the clock selection circuit 268 to provide the clock reference signal 1 39A as the μθ charge pump clock 276 to the μθ charge pump circuit 262. In this mode of operation, switching between various phases of operation in the μθ charge pump circuit 262 may be relatively stable. Alternatively, in still other embodiments of the pseudo-envelope follower power management system 1 0E, the clock selection circuit 268 is configured to provide the fixed frequency reference clock as the μθ charge pump clock 276.

[00294] In addition, the controller 50 may further provide an FLL circuit control signal 292 to govern the operation of the FLL circuit 54 of the multi-level charge pump buck converter 1 2C. The FLL circuit control signal 292 may include one or more control signals used to configure the FLL circuit 54. Via the FLL circuit control signal 292, the controller 50 may configure various time constants and control parameters resident in the FLL circuit 54 (not shown) to optimally extract the operating frequency of the multi-level charge pump buck converter 1 2C so as to reduce the overall voltage ripple that occurs at the power amplifier supply voltage V_Cc- The configuration of the FLL circuit 54 may depend upon various factors, including, but not limited to the maximum expected parallel amplifier supply voltage V_CC_MAX_, the minimum expected parallel amplifier supply voltage V_CC_MIN, the expected waveform generated by the power amplifier, the envelope and signal transmission characteristics of the signal to be transmitted, the peak-to-average ratio of the envelope of the signal to be transmitted, the data rate, the bandwidth of the channel and/or the type of modulation used to the desired waveform. Moreover, controller 50 may configure the FLL circuit 54 to minimize the overall noise or output ripple.

[00295] The parallel amplifier power source selection circuit 272 is configured to receive the internal charge pump node parallel amplifier supply from the multi-level charge pump circuit 258, of the multi-level charge pump buck converter 1 2C, or the μθ charge pump circuit output voltage, ν_μ0 OUT; which is generated at the μθ charge pump output. The parallel amplifier power source selection circuit 272 may be configured to be operably coupled to the controller 50 via a source selection control signal. Via the source selection control signal, the controller 50 may configure the parallel amplifier power source selection circuit 272 to select a desired input supply from either the internal charge pump node parallel amplifier supply or the μθ charge pump output, to be provided as the parallel amplifier supply voltage V_SUPPLY_PARA_AMP to the parallel amplifier circuit 32.

[00296] In an alternative embodiment of the pseudo-envelope follower power management system 1 0C, the parallel amplifier power source selection circuit 272 may be eliminated in the case where the internal charge pump node parallel amplifier supply or the μθ charge pump output are directly coupled to the parallel amplifier supply, V_SUPPLY_PARA_AMP. For example, some embodiments of the multi-level charge pump buck converter 1 2C may include a multi-level charge pump that does not provide an internal charge pump node parallel amplifier supply as an output. In this case, the μθ charge pump output of the μθ charge pump circuit 262 is directly coupled to the parallel amplifier circuit 14C to provide the parallel amplifier supply voltage V_SUPPLY_PARA_AMP, as the operational voltage for the parallel amplifier 35 and associated circuitry.

[00297] In addition, similar to the parallel amplifier circuit 1 4A-1 4B of Figures 2A-2B, the parallel amplifier circuit 1 4D may also include an embodiment of the VOFFSET loop circuit 41 as VOFFSET load circuit 41 B. The VOFFSET load circuit 41 B may be configured to regulate the offset voltage, VOFFSET, that is developed across the coupling circuit 1 8. Similar to the VOFFSET loop circuit 41 of Figures 2A-2B, the VOFFSET loop circuit 41 B may provide a threshold offset current, ITHRESHOLD_OFFSET, 42 to the switcher control circuit 52 of the multi-level charge pump converter 1 2C, where the threshold offset current, ITHRESHOLD_OFFSET, 42 provides an estimate of the magnitude of the offset voltage, VOFFSET, appearing across the coupling circuit 1 8.

[00298] The VOFFSET loop circuit 41 B may include a summing circuit 300, a VOFFSET target signal section circuit 308, a pre-filter 31 3, and an integrator with zero compensation 31 4 operably configured to generate the threshold offset current, ITHRESHOLD_OFFSET, 42 based upon the power amplifier supply voltage, Vcc, the parallel amplifier output 32A, and a VOFFSET target signal 302. The V- OFFSET target signal section circuit 308 may include a first input configured to receive a target offset voltage, VOFFSET TARGET_J parameter, a second input configured to receive the V_RAMP signal, and a third input configured to receive a filtered V_RAMP signal from the pre-filter 31 3. The VOFFSET target signal section circuit 308 may be configured to receive a target selection signal 31 0 from the controller 50. Based upon the target selection signal 31 0 received from the controller 50, the VOFFSET target signal section circuit 308 provides one of the target offset voltage, V₀FFSET_TARGET, parameter, the V_RAMP signal, or the the filtered V_RAMP signal as a VOFFSET target signal 302 to the summing circuit 300. In some alternative embodiments, the target signal section circuit 308 may be controlled via a VOFFSET control bus 31 2 that is coupled to the VOFFSET loop circuit 41 B.

[00299] The prefilter 31 3 may be similar to the frequency pre-distortion circuit 254 of Figure 1 0A. Similar to the pre-distortion circuit 254, the prefilter 31 3 may include a frequency equalizer circuit that includes programmable time constants. Illustratively, the programmable time constants may include a programmable pole time constant, Tau_P, and a programmable zero time constant, Tauz. The controller 50 may adjust the values of the programmable pole time constant, Taup, and a programmable zero time constant, Tauz, to adjust the frequency response of the pre-filter 31 3. In some embodiments of the parallel amplifier circuit 1 4D, the output of the frequency pre-distortion circuit 254 may be used as the third input to the VOFFSET target signal section circuit 308 instead of providing a dedicated prefilter 31 3.

[00300] The summing circuit 300 may include a positive terminal operably coupled to the power amplifier supply voltage, V_Cc- a first negative terminal coupled to the parallel amplifier output 32A, and a second negative terminal configured to receive the VOFFSET target signal 302. The summing circuit 302 subtracts the parallel amplifier output 32A and the VOFFSET target signal from the power amplifier supply voltage, V_Cc, to generate a VOFFSET error signal 304. The VOFFSET error signal 304 may be provided to the integrator with zero

compensation 31 4, which filters the VOFFSET error signal 304 to generate a threshold offset current, ITHRESHOLD OFFSET, 42. [00301 ] The VOFFSET loop circuit 41 B may be configured to create an almost constant DC voltage across the coupling circuit 18 in order to shift the power amplifier supply voltage, V_Cc_, down by a fixed amount in order to minimize the peak voltage present at the parallel amplifier output 32A.

[00302] As discussed with respect to the various embodiments of the switcher control circuit depicted in Figures 3A-C and E-G, Figures 4A-C and E-G, Figures 5A-C and E-G, and Figures 6A-C, the shunt level threshold 124, the series level threshold 126, the first boost level threshold 128, and a second boost level threshold 128 may be offset by threshold offset current, ITHRESHOLD_OFFSET, which is generated by the VOFFSET loop circuit 41 B to control the offset voltage, VOFFSET, across the coupling circuit 18, as depicted in Figures 18A-D.

[00303] The integrator with zero compensation 314 may include a filter having a first time constant, Tau₀, and a second time constant, Tau-i . The integrator with zero compensation 314 may have a filter response that is equivalent to a Laplace transfer function equal to [(1 +Tau₀* s)/(Taui ^*s)]. The values of the first time constant, Tau₀, and a second time constant, Tau-i . May be programmed by the controller 50 via the VOFFSET control bus 312. The values of the first time constant, Tau₀, and a second time constant, Tau-i.may be selected to optimize the bandwidth of the VOFFSET loop circuit to provide loop stability and a desired response time depending upon the capacitance of the coupling circuit 18 across which the offset voltage, VOFFSET, is developed.

[00304] In addition, the VOFFSET loop circuit 41 B may further be configured to permit selection of the value of the first time constant, Tau₀, and a second time constant, Tau-i , dependent upon whether the coupling circuit 18 requires pre- charging before initiation of a data burst to be sent by the linear RF power amplifier 22 (depicted in Figures 1 A-B and 2A-B). For example, if the data burst to be sent is a first data burst of the transmission, the controller 50 may determine that the coupling circuit 18 requires pre-charging prior to transmission of the first data burst.

[00305] In some embodiments of the VOFFSET loop circuit 41 B, the controller 50 may store a first startup time constant, Tau₀_startup, and a second startup time constant, Taui_startup, as local parameters. The VOFFSET loop circuit 41 B may be configured to use the first startup time constant, Tau₀_startup, and the second startup time constant, Taui_startup, during a pre-charging phase of operation of the VOFFSET loop circuit 41 B. When the VOFFSET loop circuit 41 B is configured to operate using the first startup time constant, Tau₀_startup, as the first time constant, Tau₀, and the second startup time constant, Taui_startup, as the second time constant, Tau-i, the operational bandwidth of the VOFFSET loop circuit 41 B is increased to permit faster pre-charging of the coupling circuit 1 8.

[00306] In addition, in some embodiments of the VOFFSET loop circuit 41 B, the controller 50 may store a first normal time constant, Tau₀_normal, and a second normal time constant, Tau-i_normal, as local parameters in the VOFFSET loop circuit 41 B. When the VOFFSET loop circuit 41 B is configured to operate using the first normal constant, Tau₀_normal, as the first time constant, Tau₀, and the second normal time constant, Tau-i_normal, as the second time constant, Tau-i, the operational bandwidth of the VOFFSET loop circuit 41 B is decreased to operate in a normal mode of operation.

[00307] Some embodiments of the VOFFSET loop circuit 41 B may include a pre-charge mode of operation that permits the controller to place the VOFFSET loop circuit 41 B into a pre-charge mode of operation for a predetermined period of time. For example, the VOFFSET loop circuit 41 B may include a pre-charge timer (not shown) that may be programmed by the controller 50 to generate a timer event after a predetermined time period. When in the pre-charge mode of operation, the VOFFSET loop circuit 41 B uses the first startup time constant, Tau₀_startup, as the first time constant, Tau₀, and the second startup time constant, Taui_startup, as the second time constant, Tau-i , which increases the operational bandwidth of the VOFFSET loop circuit 41 B. As an example, when starting from power-off mode to active mode, the time constant of the VOFFSET loop circuit 41 B may be programmatically reduced by the controller 50 by up to a factor of five to allow a quick initial pre-charging of the coupling circuit 1 8. For example, pre-charging may be done prior to the beginning of a transmission-slot in order to reduce the time to have the voltage complete settled to the target value for the first power-up. As an example, the transmission-slot may be a burst transmission-slot in which data is transmitted by the linear RF power amplifier. The controller 50 may configure the VOFFSET Loop Circuit 41 B to operate in a higher bandwidth during the initial pre-charging of reactive components of the coupling circuit 1 8.

In some cases, the loop bandwidth of the VOFFSET Loop Circuit 41 B may be set to provide up to five times the bandwidth used at the beginning of a burst transmission time-slot. The controller 50 operably re-configures the VOFFSET Loop Circuit 41 B back to a lower or operational bandwidth at the beginning of the burst transmission slot. In other alternative embodiments of the pseudo-envelop follower power management system, the controller 50 operably re-configures the VOFFSET Loop Circuit 41 B to have a bandwidth between 3 and 7 times the bandwidth used at the beginning of a burst transmission time-slot.

Advantageously, configuring the VOFFSET Loop Circuit 41 B to operate with a higher loop bandwidth during initial pre-charging of the reactive components of the coupling circuit 1 8 decreases the startup delay of the pseudo-envelop follower power management system, which may result in an improved overall power efficiency.

The VOFFSET Loop Circuit 41 B may be monitored and modified in a dynamic fashion. For example, the timing/filter parameters associated with the Integrator with Zero Compensation Circuit and desired VOFFSET voltage, set by the VOFFSET TARGET parameter, may be monitored and modified by controller 50 on a burst time-slot basis.

[00308] The VOFFSET Loop Circuit 41 B may be configured to operate in a higher loop band width mode of operation when no modulation is present on Vramp signal. For example, at either the beginning of the slot or between inter- slot, when the V_RAMP signal is inactive, the controller 50 may configure the

VOFFSET Loop Circuit 41 B to operate in a higher bandwidth mode of operation to improve initial startup regulation of the offset voltage, VOFFSET- Alternatively, or in addition, the VOFFSET Loop Circuit 41 B may be configured to switch from the

VOFFSET loop higher loop bandwidth mode of operation to VQFFSET loop higher loop band width mode of operation when no modulation is present. As another example, the controller 50 may program the pre-charge timer (not shown) to trigger an event after a predetermined pre-charge time period. Upon the trigger event, the VOFFSET loop circuit 41 B may be automatically re-configured to set the first normal time constant, Tau₀, to be equal to Tau₀_normal and the second time constant, Tau-i , to be equal to Tau-i_normal. As a result, after the predetermined pre-charge time period, the VOFFSET loop circuit 41 B is re-configured to operate with a normal bandwidth to ensure loop stability. This has the advantage of permitting the VOFFSET loop circuit 41 B to operate in a higher bandwidth mode during pre-charging and in a lower bandwidth mode during normal operation without requiring the controller 50 to reconfigure the VOFFSET loop circuit 41 B after a predetermined pre-charge period of time to operate in a mode having a bandwidth that is appropriate for normal operation of the pseudo-envelop follower power management system.

[00309] In the various embodiments of the switcher control circuit depicted in Figures 3A-C and E-G, Figures 4A-C and E-G, Figures 5A-C and E-G, and Figures 6A-C, threshold offset current, I THRESHOLD_OFFSET_J generated by the

VOFFSET loop circuit is generally used to raise and lower the point at which the first comparator 140, the second comparator 142, the third comparator 144, and the fourth comparator 146 trigger. However, in some alternative embodiment threshold detector and control circuits 1 32A-C and E-G, the threshold offset current, ITHRESHOLD_OFFSET, may be used to only shift the triggering threshold of less than all of the comparators 140-146. For example, referring to Figure 4C, the threshold detector and control circuit 1 32C may be reconfigured such that the threshold offset current, ITHRESHOLD_OFFSET, only shifts the triggering threshold of the second comparator 142. The effect is to only shift the triggering threshold of the comparator associated with the series level threshold 1 26 based upon the threshold offset current, ITHRESHOLD_OFFSET- Similarly, as another example of an alternative embodiment, the threshold detector and control circuit 1 32G, depicted in Figure 4G, may be reconfigured such that the threshold offset current,

ITHRESHOLD_OFFSET, only shifts the triggering threshold of the first comparator 140. The effect is to only shift the triggering threshold of the comparator associated with the shunt level threshold 124 based upon the threshold offset current,

ITHRESHOLD_OFFSET-

[00310] the shunt level threshold 124, the series level threshold 126, the first boost level threshold 128, and a second boost level threshold 128 may be offset by threshold offset current, I THRESHOLD_OFFSET_J which is generated by the VOFFSET loop circuit 41 B to control the offset voltage, VOFFSET, across the coupling circuit 18, as depicted in Figures 18A-D.

[0031 1 ]

[00312] The battery level sense circuit 264 may be coupled to the controller 50 via the battery level sense signal. The battery level sense circuit 264 may be operably configured to measure or determine the voltage level of the battery, (VBAT)- The voltage measured or determined voltage level of the battery may be provided to or obtained by the controller 50 via the battery level sense circuit. In alternative embodiments, not shown, the battery level sense circuit 264 may be configured to interface with the controller 50 via a control bus. Accordingly, the controller may use the voltage level of the battery, (VBAT), to configure the various operational components of the pseudo-envelope follower power management system 10E.

[00313] Figure 18A further depicts another embodiment of a pseudo- envelop follower power management system 10C that is similar to the

embodiment of a pseudo-envelope follower power management system 10E except that the parallel amplifier circuit 14D is replaced by the parallel amplifier circuit 41 C. The parallel amplifier circuit 41 C is similar to the parallel amplifier circuit 14C except that the VOFFSET loop circuit 41 B is replaced by the VOFFSET loop circuit 41 A. The VOFFSET loop circuit 41 A is operably configured to operate in a similar fashion as the VOFFSET loop circuit 41 B except that the integrator with zero compensation circuit is replaced with a K_ERROR_GAIN circuit 306 configured to receive the VOFFSET error signal 304 from the summing circuit 300. The

KERROR_GAIN circuit 306 may be configured to multiply the VOFFSET error signal 304 by a K_ERROR_GAIN parameter to generate the threshold offset current, ITHRESHOLD_OFFSET, 42. The controller 50 may be configured to modify the

KERROR_GAIN parameter dependent upon the operational needs of the linear RF power amlifier.

[00314] While the pseudo-envelope follower power management systems 10C of Figure 18A and 10E of Figure 18B only depicts the respective parallel amplifier circuits14C and 14D providing the scaled parallel amplifier output current estimate, I PARA_AMP_SENSE, as a feedback signal to the switcher control circuit 52 of the multi-level charge pump buck converter 12C, this is by example and not limitation. Accordingly, some embodiments of the pseudo-envelope follower power management systemsl 0D-E may further include an open loop assist circuit similar to the open loop assist circuit 39, as depicted in Figures 2A- B. In this case, as shown in Figures 2A-B, the scaled parallel amplifier output current estimate, I PARA_AMP_SENSE, is combined with the open loop assist circuit output current estimate, IASSIST_SENSE, (depicted in Figures 2A-B), to form the parallel amplifier circuit output current estimate, I PAWA OUT EST; 40, which is used as a feedback signal to the switcher control circuit 52. Accordingly, the switcher control circuit 52 and operation of the multi-level charge pump buck converter 12C depicted in Figures 18A-B may also incorporate various combinations of the operational features and functions of the embodiments of the switch control circuits 52A-D of Figures 3A-D, the threshold detector and control circuits 132A- D of Figures 4A-D, and the circuitry and state machines associated with the logic circuits 148A-D of Figures 4A-D.

[00315] Figure 18C depicts a pseudo-envelope follower power

management system 10D that is similar to the pseudo-envelope follower power management system 10C of Figure 18A. However, unlike the pseudo-envelope follower power management system 10C of Figure 18A, the multi-level charge pump buck converter 12C is replaced by a buck converter 13A.

[00316] In addition, because the buck converter 13A does not include the multi-level charge pump buck converter 12C, the parallel amplifier power source selection circuit 272 is eliminated and the μθ charge pump output of the μθ charge pump circuit 262 is directly coupled to the parallel amplifier circuit 14E in order to provide the parallel amplifier supply voltage, V_SUPPLY_PARA_AMP to the parallel amplifier 35.

[00317] The buck converter 13A is similar to the multi-level charge pump buck converter 12C except the multi-level charge pump circuit 258 is eliminated and the switcher control circuit 52 is replaced by switcher control circuit 259. Like the switcher control circuit 52, the switcher control circuit 259 provides a series switch control signal 66 and a shunt switch control signal 68 to the switching circuit 58. In addition, the switcher control circuit 259 is further configured to receive the threshold offset signal, ITHRESHOLD_OFFSET, 42 from the VOFFSET loop circuit 41 A.

[00318] Although the embodiment of the pseudo-envelope follower power management system 10D depicted in Figure 18C only depicts the switcher control circuit 259 receiving the scaled parallel amplifier output current estimate, l pARA_AMP_sENSE, as discussed above with respect to the embodiments of the pseudo-envelope follower power management system 10C and 10E of Figures 18A-B, this is by example and not by limitation. Some embodiments of the parallel amplifier circuit 14C of Figure 18C may further include an open loop assist circuit 39, as depicted in Figures 2A-B. Accordingly, in those cases where an open loop assist circuit is included in the parallel amplifier circuit 14C, as shown in Figures 2A-B, the scaled parallel amplifier output current estimate, l pARA_AMP_sENSE, is combined with the open loop assist circuit output current estimate, IASSIST_SENSE, (depicted in Figures 2A-B), to form the parallel amplifier circuit output current estimate, IPAWA_OUT_EST, 40, that may be provided as a feedback signal to the switcher control circuit 259.

[00319] Accordingly, example embodiments of the switcher control circuit 259 will now be described as depicted in Figures 3E-H. One embodiment of the switcher control circuit 259 is depicted in Figure 3E as switcher control circuit 52E. The switcher control circuit 52E is functionally similar to the switcher control circuit 52A, depicted in Figure 3A, except the circuitry associated with the multi- level charge pump circuit 56 is eliminated. As a result, the threshold detector and control circuit 132E, of Figure 3E, does not use either a first boost level threshold 128 or a second boost level threshold 130. Also, as discussed above, the parallel amplifier circuit output current estimate, I PAWA_OUT_EST_J 40 depicted in Figure 3E may be provided by the scaled parallel amplifier output current estimate, I PARA_AMP_SENSE, or, in the case where an open loop assist circuit is included in the parallel amplifier circuit 14C of Figure 1 8C, the sum of the scaled parallel amplifier output current estimate, I PARA_AMP_SENSE_J cind the open loop assist circuit output current estimate, IASSIST_SENSE-

[00320] One embodiment of the threshold detector and control circuit 1 32E is depicted in Figure 4E. The threshold detector and control circuit 1 32E may be functionally similar to the threshold detector and control circuit 132A depicted in Figure 4A except the circuitry associated with the multi-level charge pump circuit 56 is eliminated. As a result, the logic circuit 1 48E is configured to operate as a buck converter based upon the magnitude of the compensated parallel amplifier circuit output current estimate, I PAWA_COMP, relative to the shunt level threshold 1 24 and the series level threshold 1 26. In addition, unlike the threshold detector and control circuit 1 32A depicted in Figure 4A, the state machine used to control the logic circuit 148E may be simplified. Illustratively, Figure 5E depicts an example embodiment of a state machine of the logic circuit 148E.

[00321 ] Illustratively, the state machine of the logic circuit 148E may include a shunt output mode 188E and a series output mode 1 90E. In the shunt output mode 1 88E, the logic circuit 148E (Figure 4E) configures the series switch control output 1 62 such that the series switch 70 (Figure 3E) is in an open state (not conducting). The logic circuit 148E also configures the shunt switch control output 1 64 such that the shunt switch 72 is in a closed state (conducting). As a result, the switching voltage output 26 of Figure 3E is configured to provide a switching voltage, V_Sw, substantially equal to ground. In response to assertion of the series level indication 152A, which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_COMP, is greater than or equal to the series level threshold 126, the logic circuit 148A configures the state machine to transition to the series output mode 1 90E. Otherwise the state machine remains in the shunt output mode 188E. [00322] In the series output mode 190E, the logic circuit 148E configures the series switch control output 162 such that the shunt switch 70 is in a closed state (conducting). The logic circuit 148E also configures the shunt switch control output 164 such that the shunt switch 72 is in an open state (not conducting). As a result, switching voltage output 26, depicted in Figure 3A, is configured to provide a switching voltage, V_Sw, substantially equal to the direct current (DC) voltage, V_BAT, provided by the battery 20. In response to de- assertion of the shunt level indication 150A, depicted in Figure 4A, which indicates that the compensated parallel amplifier circuit output current estimate, IPAWA_COMP, is less than the shunt level threshold 124, the logic circuit 148E configures the first state machine to transition to the shunt output mode 188E, as depicted in Figure 5E.

[00323] Another embodiment of the switcher control circuit 259 is depicted in Figure 3F as switcher control circuit 52F. The switcher control circuit 52F may be functionally similar to the switcher control circuit 52B, depicted in Figure 3B, except the circuitry associated with the multi-level charge pump circuit 56 is eliminated. As a result, the threshold detector and control circuit 132F, of Figure 3F, does not use either a first boost level threshold 128 or a second boost level threshold parameter 130. Also, as discussed above, the parallel amplifier circuit output current estimate, I PAWA_OUT_EST, 40, depicted in Figure 3F, may be provided by the scaled parallel amplifier output current estimate, IPARA_AMP_SENSE, or, in the case where an open loop assist circuit is included in the parallel amplifier circuit 14C of Figure 18C, the sum of the scaled parallel amplifier output current estimate, I PARA_AMP_SENSE, and the open loop assist circuit output current estimate, IASSIST_SENSE-

[00324] One embodiment of the threshold detector and control circuit 132F of Figure 3F is further depicted in Figure 4F. The threshold detector and control circuit 132F may be functionally similar to the threshold detector and control circuit 132B, depicted in Figure 4B, except the circuitry associated with the multi- level charge pump circuit 56 is eliminated. As a result, the logic circuit 148F is configured to operate as a buck converter based upon the magnitude of the compensated parallel amplifier circuit output current estimate, I PAWA COMP_J relative to the shunt level threshold 124 and the series level threshold 126. In addition, unlike the threshold detector and control circuit 132B, depicted in Figure 4B, the state machine used to control the logic circuit 148F may be simplified. As an example, Figure 5F depicts an example embodiment of a state machine of the logic circuit 148F.

[00325] Illustratively, the state machine of the logic circuit 148F may include a shunt output mode 188F and a series output mode 190F. In the shunt output mode 188F, the logic circuit 148F, depicted in Figure 4F, configures the series switch control output 162 such that the series switch 70, depicted in Figure 3F, is in an open state (not conducting). The logic circuit 148F also configures the shunt switch control output 164 such that the shunt switch 72 is in a closed state (conducting). As a result, the switching voltage output 26 of Figure 3F is configured to provide a switching voltage, V_Sw, substantially equal to ground. In response to assertion of the series level indication 152B, which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_COMP', is greater than or equal to the series level threshold 126, the logic circuit 148F configures the state machine to transition to the series output mode 190F.

Otherwise the state machine remains in the shunt output mode 188F.

[00326] In the series output mode 190F, the logic circuit 148F configures the series switch control output 162 such that the shunt switch 70 is in a closed state (conducting). The logic circuit 148F also configures the shunt switch control output 164 such that the shunt switch 72 is in an open state (not conducting). As a result, the switching voltage output 26, depicted in Figure 3F, is configured to provide a switching voltage, V_Sw, substantially equal to the direct current (DC) voltage, V_BAT- In response to de-assertion of the shunt level indication 150B (Figure 4F), which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_COMP', is less than the shunt level threshold 124, the logic circuit 148F configures the first state machine to transition to the shunt output mode 188F, as depicted in Figure 5F. [00327] Another embodiment of the switcher control circuit 259 is depicted in Figure 3G as switcher control circuit 52G. The switcher control circuit 52G may be functionally similar to the switcher control circuit 52C, depicted in Figure 3C, except the circuitry associated with the multi-level charge pump circuit 56 is eliminated. As a result, the threshold detector and control circuit 1 32G, of Figure 3G, does not use either a first boost level threshold 1 28 or a second boost level threshold parameter 1 30. Also, as discussed above, the parallel amplifier circuit output current estimate, I PAWA_OUT_EST, 40, depicted in Figure 3G, may be provided by the scaled parallel amplifier output current estimate, IPARA_AMP_SENSE, or, in the case where an open loop assist circuit is included in the parallel amplifier circuit 1 4C of Figure 1 8C, the sum of the scaled parallel amplifier output current estimate, I PARA_AMP_SENSE, and the open loop assist circuit output current estimate, IASSIST_SENSE-

[00328] One embodiment of the threshold detector and control circuit 1 32G of Figure 3G is further depicted in Figure 4G. The threshold detector and control circuit 1 32G may be functionally similar to the threshold detector and control circuit 1 32C, depicted in Figure 4C, except the circuitry associated with the multilevel charge pump circuit 56 is eliminated. As a result, the logic circuit 1 48G is configured to operate as a buck converter based upon the magnitude of the compensated parallel amplifier circuit output current estimate, I PAWA_COMP, relative to the shunt level threshold 1 24 and the series level threshold 1 26. In addition, unlike the threshold detector and control circuit 1 32C, depicted in Figure 4C, the state machine used to control the logic circuit 1 48G may be simplified. As an example, Figure 5G depicts an example embodiment of a state machine of the logic circuit 1 48G.

[00329] Illustratively, the state machine of the logic circuit 1 48G may include a shunt output mode 1 88G and a series output mode 1 90G. In the shunt output mode 1 88G, the logic circuit 1 48G, depicted in Figure 4G, configures the series switch control output 1 62 such that the series switch 70, depicted in Figure 3G, is in an open state (not conducting). The logic circuit 1 48G also configures the shunt switch control output 1 64 such that the shunt switch 72 is in a closed state (conducting). As a result, the switching voltage output 26 of Figure 3G is configured to provide a switching voltage, V_Sw, substantially equal to ground. In response to assertion of the series level indication 152C, which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_COMP', is greater than or equal to the series level threshold 126, the logic circuit 148A configures the state machine to transition to the series output mode 190G.

Otherwise the state machine remains in the shunt output mode 188G.

[00330] In the series output mode 190G, the logic circuit 148G configures the series switch control output 162 such that the shunt switch 70 is in a closed state (conducting). The logic circuit 148G also configures the shunt switch control output 164 such that the shunt switch 72 is in an open state (not conducting). As a result, the switching voltage output 26, depicted in Figure 3G, is configured to provide a switching voltage, V_Sw, substantially equal to the direct current (DC) voltage, V_BAT- In response to de-assertion of the shunt level indication 150C, depicted in Figure 4G, which indicates that the compensated parallel amplifier circuit output current estimate, IPAWA_COMP', is less than the shunt level threshold 124, the logic circuit 148G configures the first state machine to transition to the shunt output mode 188G, as depicted in Figure 5G.

[00331 ] While Figures 3G and 4G do not depict the presence of an FLL circuit being used in combination with the switcher control circuit 52G, an embodiment of the FLL circuit may be provided for use in the buck converter in order to provide an FLL system clock 280 to either the switcher control circuit 52G or the clock management system of the pseudo-envelope follower power management system.

[00332] Another embodiment of the switcher control circuit 259 is depicted in Figure 3H as switcher control circuit 52H. The switcher control circuit 52H may be functionally similar to the switcher control circuit 52D, depicted in Figure 3D, except the circuitry associated with the multi-level charge pump circuit 56 is eliminated. Like the switcher control circuit 52D of Figure 3D, the switcher control circuit 259H provides a series switch control signal 66 and a shunt switch control signal 68 to the switching circuit 58. As a result, the threshold detector and control circuit 132H, of Figure 3H, does not use either a first boost level threshold 128 or a second boost level threshold parameter 130. Also, as discussed above, the parallel amplifier circuit output current estimate,

l pAWA_ouT_EST, 40, depicted in Figure 3H, may be provided by the scaled parallel amplifier output current estimate, I PARA_AMP_SENSE, or, in the case where an open loop assist circuit is included in the parallel amplifier circuit 14C of Figure 18C, the sum of the scaled parallel amplifier output current estimate, IPARA_AMP_SENSE, and the open loop assist circuit output current estimate, IASSIST_SENSE- [00333] One embodiment of the threshold detector and control circuit 132H of Figure 3H is further depicted in Figure 4H. The threshold detector and control circuit 132H may be functionally similar to the threshold detector and control circuit 132D, depicted in Figure 4D, except the circuitry associated with the multilevel charge pump circuit 56 is eliminated. As a result, the logic circuit 148H is configured to operate as a buck converter based upon the magnitude of the compensated parallel amplifier circuit output current estimate, I PAWA_COMP, relative to the shunt level threshold 124 and the series level threshold 126. In addition, unlike the threshold detector and control circuit 132C, depicted in Figure 4D, the state machine used to control the logic circuit 148D may be simplified. As an example, Figure 5G depicts an example embodiment of a state machine of the logic circuit 148H.

[00334] Illustratively, the state machine of the logic circuit 148H may include a shunt output mode 188H and a series output mode 190H. In the shunt output mode 188H, the logic circuit 148H, depicted in Figure 4H, configures the series switch control output 162 such that the series switch 70, depicted in Figure 3H, is in an open state (not conducting). The logic circuit 148H also configures the shunt switch control output 164 such that the shunt switch 72 is in a closed state (conducting). As a result, the switching voltage output 26 of Figure 3H is configured to provide a switching voltage, V_Sw, substantially equal to ground. In response to assertion of the series level indication 152A, which indicates that the compensated parallel amplifier circuit output current estimate, I PAWA_OUT-EST, is greater than or equal to the series level threshold 126, the logic circuit 148G configures the state machine to transition to the series output mode 190G.

Otherwise the state machine remains in the shunt output mode 188G.

[00335] In the series output mode 190H, the logic circuit 148H configures the series switch control output 162 such that the shunt switch 70 is in a closed state (conducting). The logic circuit 148H also configures the shunt switch control output 164 such that the shunt switch 72 is in an open state (not conducting). As a result, the switching voltage output 26, depicted in Figure 3H, is configured to provide a switching voltage, V_Sw, substantially equal to the direct current (DC) voltage, V_BAT- In response to de-assertion of the shunt level indication 150C, depicted in Figure 4H, which indicates that the compensated parallel amplifier circuit output current estimate, IPAWA_OUT_EST, is less than the shunt level threshold 124, the logic circuit 148H configures the first state machine to transition to the shunt output mode 188H, as depicted in Figure 5H.

[00336] While Figures 3H and 4H do not depict the presence of an FLL circuit being used in combination with the switcher control circuit 52H, an embodiment of the FLL circuit may be provided for use in the buck converter in order to provide an FLL system clock 280 to either the switcher control circuit 52G or the clock management system of the pseudo-envelope follower power management system.

[00337] Figure 18D depicts a pseudo-envelope follower power

management system 10F that is similar to the pseudo-envelope follower power management system 10E of Figure 18B. Similar to the pseudo-envelop follower power management system 10E of Figure 18B, the pseudo-envelop follower power management system 10F includes the parallel amplifier circuit 14D having the VOFFSET Loop Circuit 41 B. The various embodiments of the parallel amplifier circuit 14D, associated parallel amplifier 35, and the VOFFSET Loop Circuit 41 B are described in detail relative to the pseudo-envelop follower power management system 10E of Figure 18B, and are therefore not repeated here.

[00338] However, unlike the pseudo-envelope follower power management system 10E of Figure 18B, the multi-level charge pump buck converter 12C is replaced by a buck converter 13B. In addition, because the buck converter 13B does not include the multi-level charge pump buck converter 12C, the parallel amplifier power source selection circuit 272 is eliminated and the μθ charge pump output of the μθ charge pump circuit 262 is directly coupled to the parallel amplifier circuit 14D in order to provide the parallel amplifier supply voltage, VSUPPLY_PARA_AMP, to the parallel amplifier 35.

[00339] In addition, as discussed relative to the pseudo-envelope follower power management system 10D of Figure 18C, because the buck converter 13A does not include the a first time constant, Tau₀, and a second time constant, [00340] Figure 18A further depicts an embodiment of a VOFFSET Load Circuit 41 A configured to provide a threshold offset current, ITHRESHOLD_OFFSET, 42, to the switcher control circuit 52 of the multi-level charge pump buck converter 12C, the parallel amplifier power source selection circuit 272 is eliminated and the μC charge pump output of the μC charge pump circuit 262 is directly coupled to the parallel amplifier circuit 14D in order to provide the parallel amplifier supply voltage, V_SUPPLY_PARA_AMP to the parallel amplifier 35. In addition, switcher control circuit 259 is further configured to receive the threshold offset signal,

ITHRESHOLD_OFFSET, 42 from the VOFFSET loop circuit 41 A.

[00341 ] Also, as discussed relative to the pseudo-envelope follower power management system 10D of Figure 18C, although the embodiment of the pseudo-envelop follower power management system 10F depicted in Figure 18D only depicts the switcher control circuit 259 receiving the scaled parallel amplifier output current estimate, I PARA_AMP_SENSE, this is by example and not by limitations. Some embodiments of the parallel amplifier circuit 14D of Figure 18D may further include an open loop assist circuit 39, as depicted in Figures 2A-B. Accordingly, in those cases where an open loop assist circuit is included in the parallel amplifier circuit 14D, the scaled parallel amplifier output current estimate, l pARA_AMP_sENSE, is combined with the open loop assist circuit output current estimate, IASSIST_SENSE, (depicted in Figures 2A-B), to form the parallel amplifier circuit output current estimate, IPAWA_OUT_EST, 40, that may be provided as a feedback signal to the switcher control circuit 259. [00342] The operation of the buck converter 13A and the switcher control circuit 259 are described relative to the pseudo-envelope follower power management system 10D of Figure 18C. Accordingly, a detailed description of the operation of the buck converter 13A are omitted from the description of the pseudo-envelope follower power management system 10F of Figure 18D.

[00343] The μθ charge pump circuit 262, depicted in Figures 18A-D, will now be discussed. Figure 19A depicts an embodiment of the μθ charge pump circuit 262 of Figures 18A-D as a μθ charge pump circuit 262A. The μθ charge pump circuit 262A may be configured to generate a μθ charge pump output voltage, ν_μ0_ουτ, at the μθ charge pump output based upon an operational mode of the iC charge pump circuit 262A. The μθ charge pump circuit 262A may include four operational modes. The μθ charge pump output voltage, V_MC_OUT, generated at the μθ charge pump output may be based on an operational ratio of the [iC charge pump, μΒΒρΑτιο. As an example, the μθ charge pump circuit 262A may include four operational modes: OFF mode, 1 x V_BAT mode, 4/3 x V_BAT mode, and 3/2 x V_BAT mode, where each operational mode corresponds to a particular operational ratio of the μθ charge pump, μΒΒΒ_Ατιο- Table 1 shows, in tabulated form, the relationships between the operational modes of the μθ charge pump circuit 262A, the operational ratio of the μθ charge pump, μΒΒρΑτιο, and the μθ charge pump output voltage, V_MC_OUT, substantially generated at the [iC charge pump output.

OPERATIONAL

MODE OF RATIO OF μθ μθ CHARGE PUMP OUTPUT VOLTAGE, OPERAATION OF μθ CHARGE (ν_μ0 OUT), GENERATED AT μθ CHARGE CHARGE PUMP PUMP, PUMP OUTPUT

(μΒΒρΑτιο)

OFF Mode OFF FLOATING

1 X V_BAT Mode 1 1 X V_BAT

4/3 X V_BAT Mode 4/3 4/3 X V_BAT

3/2 X V_BAT Mode 3/2 3/2 X V_BAT

TABLE 1

[00344] When the C charge pump circuit 262A is configured to operate in the OFF mode, the C charge pump circuit 262A is disabled and the C charge pump output floats. When the C charge pump circuit 262A is configured to

operate in the 1 x V_BAT mode, the C charge pump circuit 262A is configured to generate a C charge pump output voltage, V_MC_OUT, substantially equal to the supply input 24 (V_BAT)- When the C charge pump circuit 262A is configured to operate in the 4/3 x V_BAT mode, the C charge pump circuit 262A is configured to generate a C charge pump output voltage, ν_μ0_ουτ, substantially equal to the

4/3 x VBAT- When the C charge pump circuit 262A is configured to operate in the 3/2 x VBAT mode, the C charge pump circuit 262A is configured to generate a iC charge pump output voltage, ν_μ0_ουτ, substantially equal to 3/2 x V_BAT- [00345] The C charge pump circuit 262A may include a C charge pump control circuit 31 6A, a first flying capacitor 31 8 having a first terminal 31 8A and a second terminal 31 8B, a second flying capacitor 320 having a first terminal 320A, a second terminal, 320B and a plurality of switches 322, 324, 326, 328, 330,

332, 334, 336, and 338. Each of the plurality of switches 322, 324, 326, 328,

330, 332, 334, 336, and 338 may be a solid state based switch implemented with field effect transistors, insulator-on-semiconductor based transistors, or bipolar based transistors, or a combination thereof. Each of the plurality of switches

322, 324, 326, 328, 330, 332, 334, 336, and 338 may be a solid state

transmission gate. As another example, each of the plurality of switches 322, 324, 326, 328, 330, 332, 334, 336, and 338 may be based on a GaN process. Alternatively, each of the plurality of switches 322, 324, 326, 328, 330, 332, 334, 336, and 338 may be micro-electromechanical systems (M EMS) contact type switches.

[00346] The plurality of switches 322, 324, 326, 328, 330, 332, 334, 336, and 338 may include a first switch 322, (SW 1 ), a second switch 324, (SW 2), a third switch 326, (SW 3), a fourth switch 328, (SW 4), a fifth switch 330, (SW 5), a sixth switch 332, (SW 6), a seventh switch 334, (SW 7), an eighth switch 336, (SW 8), and a ninth switch 338, (SW 9). The first switch 322 may be coupled between the first terminal 320A of the second flying capacitor 320 and the supply input 24 (VBAT)- The first switch 322, (SW 1 ), may include a first switch control input configured to receive a first switch control signal 340 from the μθ charge pump control circuit 31 6A, where the first switch control signal 340 operably opens and closes the first switch 322, (SW 1 ), based upon the operational mode of the iC charge pump circuit 262A. The second switch 324, (SW 2), may include a second switch control input configured to receive a second switch control signal 342 from the μθ charge pump control circuit 31 6A, where the second switch control signal 342 operably opens and closes the second switch 324, (SW 2), based upon the operational mode of the μθ charge pump circuit 262A. The second switch 324, (SW 2), may be coupled between the supply input 24, (VBAT), and the second terminal 320B of the second flying capacitor 320. The third switch 326, (SW 3), may include a third switch control input configured to receive a third switch control signal 344 from the μθ charge pump control circuit 31 6A, where the third switch control signal 344 operably opens and closes the third switch 326, (SW 3), based upon the operational mode of the μθ charge pump circuit 262A. The third switch 326, (SW 3), may be coupled between the second terminal 320B of the second flying capacitor 320 and ground. The fourth switch 328, (SW 4), may include a fourth switch control input configured to receive a fourth switch control signal 346 from the μθ charge pump control circuit 31 6A, where the fourth switch control signal 346 operably opens and closes the fourth switch 328, (SW 4), based upon the operational mode of the μθ charge pump circuit 262A. The fourth switch 328, (SW 4), may be coupled between the first terminal 320A of the second flying capacitor 320 and second terminal 31 8B of the first flying capacitor 31 8. The fifth switch 330, (SW 5), may include a fifth switch control input configured to receive a fifth switch control signal 348 from the μθ charge pump control circuit 31 6A, where the fifth switch control signal 348 operably opens and closes the fifth switch 330, (SW 5), based upon the operational mode of the μθ charge pump circuit 262A. The fifth switch 330, (SW 5) , may be coupled between the second terminal 31 8B of the first flying capacitor 31 8 and second terminal 320B of the second flying capacitor 320. The sixth switch 332, (SW 6), may include a sixth switch control input configured to receive a sixth switch control signal 350 from the μθ charge pump control circuit 31 6A, where the sixth switch control signal 350 operably opens and closes the sixth switch 332, (SW 6) , based upon the operational mode of theiC charge pump circuit 262A. The sixth switch 332, (SW 6), may be coupled between the first terminal 31 8A of the first flying capacitor 31 8 and first terminal 320A of the second flying capacitor 320. The seventh switch 334, (SW 7), may include a seventh switch control input configured to receive a seventh switch control signal 352 from the μθ charge pump control circuit 31 6A, where the seventh switch control signal 352 operably opens and closes the seventh switch 334 based upon the operational mode of the μθ charge pump circuit 262A. The seventh switch 334, (SW 7) , may be coupled between the second terminal 31 8B of the first flying capacitor 31 8 and ground. The eighth switch 336, (SW 8), may include an eighth switch control input configured to receive an eighth switch control signal 354 from the μθ charge pump control circuit 31 6A, where the eighth switch control signal 354 operably opens and closes the eighth switch 336, (SW 8), based upon the operational mode of the μθ charge pump circuit 262A. The eighth switch 336, (SW 8) , may be coupled between the second terminal 31 8B of the first flying capacitor 31 8 and the supply input 24, (V_BAT) - The ninth switch 338, (SW 9), may include a ninth switch control input configured to receive a ninth switch control signal 356 from the μθ charge pump control circuit 31 6A, where the ninth switch control signal 356 operably opens and closes the ninth switch 338, (SW 9), based upon the operational mode of the μθ charge pump circuit 262A. The ninth switch 338, (SW 9), may be coupled between the first terminal 318A of the first flying capacitor 318 and the supply input 24, (V_BAT)- [00347] The μθ charge pump control circuit 316A may be configured to couple to a μθ charge pump clock 276 and a μθ charge pump control bus 278. The iC charge pump control bus 278 may be used to configure the μθ charge pump circuit 262A to operate in one of the four operational modes by setting an operational ratio of the μθ charge pump, μΒΒρΑτιο, of the μθ charge pump circuit 262A, where the parameter corresponding to a selection of the operational ratio of the [iC charge pump, μΒΒρΑτιο, may be stored locally in the μθ charge pump control circuit 216A. In addition, the μθ charge pump control circuit 316A may use the μθ charge pump clock 276 to operably switch between phases of operation of the μθ charge pump circuit 262A. The switch state (open or closed) of each of the first switch 322, (SW 1 ), the second switch 324, (SW 2), the third switch 326, (SW 3), the fourth switch 328, (SW 4), the fifth switch 330, (SW 5), the sixth switch 332, (SW 6), the seventh switch 334, (SW 7), the eighth switch 336, (SW 8), and the ninth switch 338, (SW 9), may be changed depending upon the phase of operation of the μθ charge pump circuit 262A. The relationship between the operational ratio of the μθ charge pump, μΒΒρΑτιο, the phase of operation of the μθ charge pump circuit 262A, and the switch state of the first switch 322, (SW 1 ), the second switch 324, (SW 2), the third switch 326, (SW 3), the fourth switch 328, (SW 4), the fifth switch 330, (SW 5), the sixth switch 332, (SW 6), the seventh switch 334, (SW 7), the eighth switch 336, (SW 8), and the ninth switch 338, (SW 9), is shown in TABLE 2.

OPERATIONAL RATIO OF μθ CHARGE PUMP, ( JBBRATIO)

SWITCHES OFF 1 4/3 3/2

SW 1 OPEN OPEN PHASE 1 OPEN

SW 2 OPEN OPEN PHASE 2 PHASE 1

SW 3 OPEN OPEN PHASE 3 PHASE 2

SW 4 OPEN OPEN PHASE 3 PHASE 2

SW 5 OPEN OPEN PHASE 1 PHASE 1

SW 6 OPEN OPEN PHASE 2 OPEN SW 7 OPEN OPEN OPEN OPEN

SW 8 OPEN OPEN OPEN PHASE 1

SW 9 OPEN PHASE 1 OPEN OPEN

TABLE 2

[00348] As used in TABLE 2, "PHASE 1 " indicates the switch state (open or closed) of the identified switch is closed during a first phase of operation of theiC charge pump circuit 262A. "PHASE 2" indicates that the switch state (open or closed) of the identified switch is closed during a second phase of operation of the [iC charge pump circuit 262A. "PHASE 3" indicates the switch state (open or closed) of the identified switch is closed during a third phase of operation of the [iC charge pump circuit 262A. "OPEN" indicates the switch state (open or closed) of the identified switch is open during all the phases of operation of the [iC charge pump circuit 262A.

[00349] As an example, the μθ charge pump circuit 262A may be configured to operate in the OFF mode by setting the operational ratio of the μθ charge pump, BBRATIO, to OFF. When the operational ratio of the μθ charge pump, BBRATIO, is set to OFF, the first switch 322, (SW 1 ), is configured to be open, the second switch 324, (SW 2), is configured to be open, the third switch 326, (SW 3), is configured to be open, the fourth switch 328, (SW 4), is configured to be open, the fifth switch 330, (SW 5), is configured to be open, the sixth switch 332, (SW 6), is configured to be open, the seventh switch 334, (SW 7), is configured to be open, the eighth switch 336, (SW 8), is configured to be open, and the ninth switch 338, (SW 9), is configured to be open at all times. Accordingly, the μθ charge pump output voltage, V_MC_OUT, at the μθ charge pump output floats with respect to ground when the μθ charge pump circuit 262A is configured to operate in the OFF mode.

[00350] The μθ charge pump circuit 262A may be configured to operate in the 4/3 x VBAT mode by setting the operational ratio of the μθ charge pump, μΒΒρΑτιο, to 4/3. When the operational ratio of the μθ charge pump, μΒΒρΑτιο, is set to 4/3, the μθ charge pump circuit 262A may operate in a first phase, (PHASE 1 ), a second phase, (PHASE 2), and a third phase, (PHASE 3), dependent upon the μθ charge pump clock 276. Figure 20A depicts an example of the "effective" operation of the μθ charge pump circuit 262A when the μθ charge pump circuit 262A is configured to operate in either the first phase, (PHASE 1 ), the second phase, (PHASE 2), and the third phase, (PHASE 3). As depicted in Figure 20A, some embodiments of the μθ charge pump circuit 262A may include a μθ charge pump output capacitor 357, Ο_μ0_ουτ, coupled to the μθ charge pump output. In some phases of operation, the μθ charge pump output capacitor 357, Ο_μο_ουτ, may store charge transferred from supply voltage 24, (VBAT), to the μθ charge pump output. In other phases of operation, the μθ charge pump output capacitor 357, Ο_μ0_ουτ, may source previously transferred charge to the μθ charge pump output.

[00351 ] As depicted in Figure 20A, during the first phase of operation, (PHASE 1 ), of the μθ charge pump circuit 262A, when the μθ charge pump circuit 262A is configured to operate in the 4/3 x V_BAT mode, the switches of theiC charge pump circuit 262A are configured to couple the first terminal 318A of the first flying capacitor 318 to the supply voltage 24, (VBAT), the second terminal 318B of the first flying capacitor 318 to the second terminal 320B of the second flying capacitor 320, and the first terminal 320A of the second flying capacitor 320 to the μθ charge pump output. As a result, during the first phase of operation, (PHASE 1 ), of the μθ charge pump circuit 262A, the μθ charge pump circuit 262A delivers charge to the μθ charge pump output capacitor 357, Ο_μο-

_OUT,

[00352] As depicted in Figure 20B, during the second phase of operation, (PHASE 2), of the μθ charge pump circuit 262A, when the μθ charge pump circuit 262A is configured to operate in the 4/3 x V_BAT mode, the switches of the [iC charge pump circuit 262A are configured to couple the second terminal 320B of the second flying capacitor 320 to the supply voltage 24, (V_BAT), the first terminal 320A of the second flying capacitor 320 to the first terminal 318A of the first flying capacitor 318 and the μθ charge pump output, and decouple the second terminal 318B of the first flying capacitor 318 such that to the second terminal 318B of the first flying capacitor 318 floats relative to ground. As a result, during the second phase of operation, (PHASE 2), of the μθ charge pump circuit 262A, the μθ charge pump circuit 262A delivers charge to the μθ charge pump output capacitor 357, Ο_μ0_ουτ- [00353] As depicted in Figure 20C, during the third phase of operation, (PHASE 3), of the μθ charge pump circuit 262A, when the μθ charge pump circuit 262A is configured to operate in the 1 x V_BAT mode, the switches of theiC charge pump circuit 262A are configured to couple the first terminal 320A of the second flying capacitor 320 to the supply voltage 24, (V_BAT), the second terminal 320B of the second flying capacitor 320 to the first terminal 318A of the first flying capacitor 318, and the second terminal 318B of the first flying capacitor 318 to ground. In addition, during the third phase of operation, (PHASE 3), of the [iC charge pump circuit 262A, the μθ charge pump output is decoupled from the first flying capacitor 318, the second flying capacitor, and the supply voltage 24, (VBAT), such that the charge previously stored in the μθ charge pump output capacitor 357, Ο_μ0_ουτ, sources current to the μθ charge pump output.

[00354] Accordingly, returning to TABLE 2, when the μθ charge pump circuit 262A is configured to operate in the 4/3 x V_BAT mode, the first switch 322, (SW 1 ), is configured to be closed during the first phase of operation, (PHASE 1 ), the second switch 324, (SW 2), is configured to be closed during the second phase of operation, (PHASE 2), the third switch 326, (SW 3), is configured to be closed during the third phase of operation, (PHASE 3), the fourth switch 328, (SW 4), is configured to be closed during the third phase of operation, (PHASE 3), the fifth switch 330, (SW 5), is configured to be closed during the first phase of operation, (PHASE 1 ), and the sixth switch 332, (SW 6), is configured to be closed during the second phase of operation, (PHASE 2) of the μθ charge pump circuit 262A. Otherwise, the μθ charge pump control circuit 316A configures the first switch 322, (SW 1 ), the second switch 324, (SW 2), the third switch 326, (SW 3), the fourth switch 328, (SW 4), the fifth switch 330, (SW 5), the sixth switch 332, (SW 6), the seventh switch 334, (SW 7), the eighth switch 336, (SW 8), and the ninth switch 338, (SW 9), to be open. As a result, the μθ charge pump output provides a μθ charge pump output voltage, V _μο_ουτ, substantially equal to 4/3 x V_BAT-

[00355] As another example of the operation of the μθ charge pump circuit 262A depicted in Figure 1 9A, the μθ charge pump circuit 262A may be

configured to operate in the 3/2 x V_BAT mode by setting the operational ratio of the iC charge pump, μΒΒρΑτιο, to 3/2. When the operational ratio of the μθ charge pump, μΒΒρΑτιο, is set to 3/2, the μθ charge pump circuit 262A may operate in a first phase of operation, (PHASE 1 ) and a second phase of operation, (PHASE 2) dependent upon the μθ charge pump clock 276. Similar to Figures 20A-C, Figures 21 A-B depict the "effective" circuit topology of the μθ charge pump circuit 262A during the first phase of operation, (PHASE 1 ) and a second phase of operation, (PHASE 2).

[00356] Accordingly, returning to TABLE 2, when the μθ charge pump circuit 262A is configured to operate in the 3/2 x V_BAT mode, the second switch 324, (SW 2), is configured to be closed during the first phase of operation, (PHASE 1 ), the third switch 326, (SW 3), is configured to be closed during the second phase of operation, (PHASE 3), the fourth switch 328, (SW 4), is configured to be closed during the second phase of operation, (PHASE 2), the fifth switch 330, (SW 5), is configured to be closed during the first phase of operation, (PHASE 1 ), and the eighth switch 336, (SW 8), is configured to be closed during the first phase of operation, (PHASE 1 ) of the μθ charge pump circuit 262A. Otherwise, the μθ charge pump control circuit 31 6B configures the first switch 322, (SW 1 ), the second switch 324, (SW 2), the third switch 326, (SW 3), the fourth switch 328, (SW 4), the fifth switch 330, (SW 5), the sixth switch 332, (SW 6), the seventh switch 334, (SW 7), the eighth switch 336, (SW 8), and the ninth switch 338, (SW 9), to be open. As a result, the μθ charge pump output provides a μθ charge pump output voltage, V _μο_ουτ, substantially equal to 3/2 x V_BAT-

[00357] The μθ charge pump circuit 262A may also be configured to operate in the 1 x V_BAT mode by setting the operational ratio of the μθ charge pump, μΒΒρΑτιο, to 1 . When the operational ratio of the μθ charge pump, μΒΒρΑτιο, is set to 1 , the μθ charge pump circuit 262A has one phase of operation, PHASE 1 . Figure 20C depicts the "effective" circuit topology of the μθ charge pump circuit 262A during the first phase of operation, (PHASE 1 ) when the μθ charge pump circuit 262A is configured to operate in the 1 x V_BAT mode. As a result, shown in TABLE 2, the switch state of the first switch 322, (SW 1 ), the second switch 324, (SW 2), the third switch 326, (SW 3), the fourth switch 328, (SW 4), the fifth switch 330, (SW 5), the sixth switch 332, (SW 6), the seventh switch 334, (SW 7), the eighth switch 336, (SW 8), and the ninth switch 338, (SW 9), do not change over time. Accordingly, when the μθ charge pump circuit 262A

configured to operate in the 1 x V_BAT mode, the first switch 322, (SW 1 ), is configured to be open, the second switch 324, (SW 2), is configured to be open, the third switch 326, (SW 3), is configured to be open, the fourth switch 328, (SW 4), is configured to be open, the fifth switch 330, (SW 5), is configured to be open, the sixth switch 332, (SW 6), is configured to be open, the seventh switch 334, (SW 7), is configured to be open, the eighth switch 336, (SW 8), is configured to be open, and the ninth switch 338, (SW 9), is configured to be closed at all times. As a result, the μθ charge pump output generates a μθ charge pump output voltage, ν_μ0_ουτ, substantially equal to 1 x V_BAT because closing the ninth switch 338, (SW 9), couples the supply voltage 24, (V_BAT), to theiC charge pump output.

[00358] Figure 19B depicts another example embodiment of the μθ charge pump circuit 262 of Figures 18A-D as a μθ charge pump circuit 262B. Similar to the [iC charge pump circuit 262A of Figure 19A, the μθ charge pump circuit 262B may be configured to generate a μθ charge pump output voltage, V_MC_OUT, at the μθ charge pump output based upon an operational mode of the μθ charge pump circuit 262B. However, unlike the μθ charge pump circuit 262A, the μθ charge pump circuit 262B may be configured to either "boost" or "buck" the supply voltage 24, (V_BAT) to generate the μθ charge pump output voltage, ν_μο_ουτ, at the μθ charge pump output. As an example, the operational modes of the [iC charge pump circuit 262B may include an OFF mode, a 1 /4 x V_BAT mode, 1 /3 x V_BAT mode, a 1 /2 x V_BAT mode, a 2/3 x V_BAT mode, 1 x V_BAT mode, a 4/3 x VBAT mode, and a 3/2 x V_BAT mode, where each of the operational modes of the iC charge pump circuit 262B corresponds to a particular operational ratio of the [iC charge pump, μΒΒ_ΒΑτιο- Table 3 shows, in tabulated form, the

relationships between the operational modes of the θ charge pump circuit 262B, the operational ratio of the θ charge pump, μΒΒρΑτιο, and the θ charge pump output voltage, ν_μ0_ουτ, substantially generated at the θ charge pump output.

[00359] The operational modes of the θ charge pump circuit 262B are now described. As an example, when the θ charge pump circuit 262B is configured to operate in the OFF mode, the θ charge pump circuit 262B is disabled and the θ charge pump output floats. When the θ charge pump circuit 262B is configured to operate in the 1 /4 x V_BAT mode, the θ charge pump circuit 262B is configured to generate a θ charge pump output voltage, ν_μ0_ουτ, substantially equal to 1/4 x the supply input 24 (VBAT)- When the θ charge pump circuit 262B is configured to operate in the 1 /3 x V_BAT mode, the θ charge pump circuit 262B is configured to generate an θ charge pump output voltage, V _μο_ουτ, substantially equal to 1 /3 x V_BAT- When the θ charge pump circuit 262B is configured to operate in the 1 /2 x V_BAT mode, the θ charge pump circuit 262B is configured to generate a θ charge pump output voltage, V _μο_ουτ, substantially equal to 1/2 x V_BAT- When the θ charge pump circuit 262B is configured to operate in the 2/3 x V_BAT mode, the μθ charge pump circuit 262B is configured to generate an μθ charge pump output voltage, V _μο_ουτ, substantially equal to 2/3 x V_BAT- When the μθ charge pump circuit 262B is configured to operate in the 1 x V_BAT mode, the μθ charge pump circuit 262B is configured to generate an μθ charge pump output voltage, ν_μ0_ουτ, substantially equal to 1 x VBAT- When the μθ charge pump circuit 262B is configured to operate in the 4/3 x VBAT mode, the μθ charge pump circuit 262B is configured to generate an μθ charge pump output voltage, V _μο_ουτ, substantially equal to 4/3 x V_BAT- And, when the μθ charge pump circuit 262B is configured to operate in the 3/2 x V_BAT mode, the μθ charge pump circuit 262B is configured to generate a μθ charge pump output voltage, V_MC_OUT, substantially equal to 3/2 x V_BAT- [00360] The μθ charge pump circuit 262B may include a μθ charge pump control circuit 31 6B, a first flying capacitor 358 having a first terminal 358A and a second terminal 358B, a second flying capacitor 360 having a first terminal 360A and a second terminal 360B, a first switch 362, (SW 1 ), a second switch 364, (SW 2), a third switch 366, (SW 3), a fourth switch 368, (SW 4), a fifth switch 370, (SW 5), a sixth switch 372, (SW 6), a seventh switch 374, (SW 7), an eighth switch 376, (SW 8), a ninth switch 378, (SW 9), a tenth switch 380, (SW 10), an eleventh switch 382, (SW 1 1 ), a twelfth switch 384, (SW 1 2), and a thirteenth switch 386, (SW 1 3). Each of the plurality of switches of the μθ charge pump circuit 262B may be a solid state based switch implemented with field effect transistors, insulator-on-semiconductor based transistors, or bipolar based transistors, or a combination thereof. Each of the plurality of switches of the μθ charge pump circuit 262B may be a solid state transmission gate. As another example, each of the plurality of switches of the μθ charge pump circuit 262B may be based on a GaN process. Alternatively, each of the plurality of switches of the iC charge pump circuit 262B may be micro-electromechanical systems (MEMS) contact type switches.

[00361 ] As depicted in Figure 19B, the first switch 362, (SW 1 ), may be coupled between the first terminal 358A of the first flying capacitor 358 and the supply input 24 (V_BAT)- The first switch 362, (SW 1 ), may include a first switch control input configured to receive a first switch control signal 388 from the μθ charge pump control circuit 31 6B, where the first switch control signal 388 operably opens and closes the first switch 362, (SW 1 ), based upon the operational mode of the μθ charge pump circuit 262B. The first switch 362, (SW 1 ), may be coupled between the supply input 24, (V_BAT), and the first terminal 358A of the first flying capacitor 358. The second switch 364, (SW 2), may include a second switch control input configured to receive a second switch control signal 390 from the μθ charge pump control circuit 31 6B, where the second switch control signal 390 operably opens and closes the second switch 364, (SW 2), based upon the operational mode of the μθ charge pump circuit 262B. The second switch 364, (SW 2), may be coupled between the first terminal 358A of the first flying capacitor 358 and the μθ charge pump output. The third switch 366, (SW 3), may include a third switch control input configured to receive a third switch control signal 392 from the μθ charge pump control circuit 31 6B, where the third switch control signal 392 operably opens and closes the third switch 366, (SW 3), based upon the operational mode of the μθ charge pump circuit 262B. The third switch 366, (SW 3), may be coupled between the second terminal 358B of the first flying capacitor 358 and ground. The fourth switch 368, (SW 4), may include a fourth switch control input configured to receive a fourth switch control signal 394 from the μθ charge pump control circuit 31 6BA, where the fourth switch control signal 394 operably opens and closes the fourth switch 368, (SW 4), based upon the operational mode of the μθ charge pump circuit 262B. The fourth switch 368, (SW 4), may be coupled between the second terminal 358B of the first flying capacitor 358 and the μθ charge pump output. The fifth switch 370, (SW 5), may include a fifth switch control input configured to receive a fifth switch control signal 396 from the μθ charge pump control circuit 31 6B, where the fifth switch control signal 396 operably opens and closes the fifth switch 370, (SW 5), based upon the operational mode of the μθ charge pump circuit 262B. The fifth switch 370, (SW 5), may be coupled between the second terminal 358B of the first flying capacitor 358 and first terminal 360A of the second flying capacitor 360. The sixth switch 372, (SW 6), may include a sixth switch control input configured to receive a sixth switch control signal 398 from the μθ charge pump control circuit 31 6B, where the sixth switch control signal 398 operably opens and closes the sixth switch 372, (SW 6), based upon the operational mode of the μθ charge pump circuit 262B. The sixth switch 372, (SW 6), may be coupled between the first terminal 360A of the second flying capacitor 360 and the supply input 24, (V_BAT)- The seventh switch 374, (SW 7), may include a seventh switch control input configured to receive a seventh switch control signal 400 from the μθ charge pump control circuit 31 6B, where the seventh switch control signal 400 operably opens and closes the seventh switch 374, (SW 7), based upon the operational mode of the μθ charge pump circuit 262B. The seventh switch 374, (SW 7), may be coupled between the first terminal 360A of the second flying capacitor 380 and the μθ charge pump output. The eighth switch 376, (SW 8), may include an eighth switch control input configured to receive an eighth switch control signal 402 from theiC charge pump control circuit 31 6B, where the eighth switch control signal 402 operably opens and closes the eighth switch 376, (SW 8), based upon the operational mode of the μθ charge pump circuit 262B. The eighth switch 376, (SW 8), may be coupled between the second terminal 360B of the second flying capacitor 360 and ground. The ninth switch 378, (SW 9), may include a ninth switch control input configured to receive a ninth switch control signal 404 from the [iC charge pump control circuit 31 6B, where the ninth switch control signal 404 operably opens and closes the ninth switch 378, (SW 9), based upon the operational mode of the μθ charge pump circuit 262B. The ninth switch 378, (SW 9), may be coupled between the second terminal 360B of the second flying capacitor 360 and the μθ charge pump output. The tenth switch 380, (SW 1 0), may include a tenth switch control input configured to receive a tenth switch control signal 406 from the μθ charge pump control circuit 31 6B, where the tenth switch control signal 406 operably opens and closes the tenth switch 380, (SW 1 0), based upon the operational mode of the μθ charge pump circuit 262B. The tenth switch 380, (SW 1 0), may be coupled between the first terminal 358A of the first flying capacitor 358 and the first terminal 360A of the second flying capacitor 360. The eleventh switch 382, (SW 1 1 ), may include a eleventh switch control input configured to receive a eleventh switch control signal 408 from the μθ charge pump control circuit 31 6B, where the eleventh switch control signal 408 operably opens and closes the eleventh switch 382, (SW 1 1 ), based upon the operational mode of the μθ charge pump circuit 262B. The eleventh switch 382, (SW 1 1 ), may be coupled between the second terminal 358B of the first flying capacitor 358 and the supply input 24, (V_BAT)- The twelfth switch 384, (SW 1 2), may include a twelfth switch control input configured to receive a twelfth switch control signal 41 0 from the μθ charge pump control circuit 31 6B, where the twelfth switch control signal 41 0 operably opens and closes the twelfth switch 384, (SW 12), based upon the operational mode of the μθ charge pump circuit 262B. The twelfth switch 384, (SW 1 2), may be coupled between the second terminal 360B of the second flying capacitor 360 and the supply input 24, (V_BAT)- The thirteenth switch 386, (SW 13), may include a thirteenth switch control input configured to receive an thirteenth switch control signal 41 2 from the μθ charge pump control circuit 31 6B, where the thirteenth switch control signal 41 2 operably opens and closes the thirteenth switch 386, (SW 1 3), based upon the operational mode of the μθ charge pump circuit 262B. The thirteenth switch 386, (SW 1 3), may be coupled between the second terminal 358B of the first flying capacitor 358 and the second terminal 360B of the second flying capacitor 360. Although not depicted in Figure 1 9B, some embodiments of the μθ charge pump circuit 262B further include a μθ charge pump output capacitor 357, Ο_μο_ουτ, coupled to the iC charge pump output in order to either store charge transferred from the supply voltage 24, (V_BAT), to the μθ charge pump output or may source

previously transferred charge to the μθ charge pump output, as previously described relative to the operation of the μθ charge pump circuit 262A.

[00362] Similar to the μθ charge pump circuit 262A, the μθ charge pump circuit 262B may be configured to operate in a respective operational mode based upon selection of an operational ratio of the μθ charge pump, μΒΒρΑτιο, that corresponds to the respective operational mode. Also, similar to TABLE 2,

TABLE 4 provides the relationship between the operational ratio of the μθ charge pump, BBRATIO, the phase of operation, and the switch state (open or closed) of the first switch 362, (SW 1 ), the second switch 364, (SW 2), the third switch 366, (SW 3), the fourth switch 368, (SW 4), the fifth switch 370, (SW 5), the sixth switch 372, (SW 6), the seventh switch 374, (SW 7), the eighth switch 376, (SW 8), the ninth switch 378, (SW 9), the tenth switch 380, (SW 1 0), the eleventh switch 382, (SW 1 1 ), the twelfth switch 384, (SW 1 2), and the thirteenth switch 386, (SW 13).

TABLE 4

[00363] Similar to TABLE 2, in TABLE 4, "PHASE 1 " indicates the switch state (open or closed) of the identified switch is closed during a first phase of operation of the μθ charge pump circuit 262B. "PHASE 2" indicates the switch state (open or closed) of the identified switch is closed during a second phase of operation of the μθ charge pump circuit 262B. "PHASE 3" indicates the switch state (open or closed) of the identified switch is closed during a third phase of operation of the μθ charge pump circuit 262B. "OPEN" indicates the switch state (open or closed) of the identified switch is open during all the phases of operation of the iC charge pump circuit 262B.

[00364] Similar to the μθ charge pump control circuit 316A, the controller 50, depicted in Figures 18A-D, may configure the μθ charge pump control circuit 316B via the μθ charge pump control bus 278 to operate in one of the

operational modes, as shown in TABLE 3, by setting an operational ratio of the [iC charge pump, μΒΒρΑτιο, of the μθ charge pump circuit 262B. Also similar to the [iC charge pump control circuit 316A, the μθ charge pump control circuit 316B may store one or more parameters corresponding to a selection of the operational ratio of the μθ charge pump, μΒΒρΑτιο, locally in the μθ charge pump control circuit 316B.

[00365] As an example, similar to the μθ charge pump circuit 262A, the μθ charge pump circuit 262B may be configured to operate in the OFF mode by setting the operational ratio of the μθ charge pump, μΒΒρΑτιο, to OFF. When the operational ratio of the μθ charge pump, μΒΒρΑτιο, is set to OFF, the first switch 362, (SW 1 ), is configured to be open, second switch 364, (SW 2), is configured to be open, the third switch 366, (SW 3), is configured to be open, the fourth switch 368, (SW 4), is configured to be open, the fifth switch 370, (SW 5), is configured to be open, the sixth switch 372, (SW 6), is configured to be open, the seventh switch 374, (SW 7), is configured to be open, the eighth switch 376, (SW 8), is configured to be open, the ninth switch 378, (SW 9), is configured to be open, the tenth switch 380, (SW 10), is configured to be open, the eleventh switch 382, (SW 1 1 ), is configured to be open, the twelfth switch 384, (SW 12), is configured to be open, and the thirteenth switch 386, (SW 13), is configured to be open at all times. Accordingly, the μθ charge pump output voltage, V _μο_ουτ, at the iC charge pump output floats with respect to ground when the μθ charge pump circuit 262A is configured to operate in the OFF mode.

[00366] Also similar to the μθ charge pump circuit 262A, the μθ charge pump circuit 262B may be configured to operate in the 3/2 x V_BAT mode by setting the operational ratio of the μθ charge pump, μΒΒρΑτιο, to 3/2. As indicated in Table 4, similar to the operation of the μθ charge pump circuit 262A, when the operational ratio of the μθ charge pump, μΒΒρΑτιο, is set to 3/2, the μθ charge pump circuit 262B may operate in a first phase of operation, (PHASE 1 ) and a second phase of operation, (PHASE 2) dependent upon the μθ charge pump clock 276.

[00367] Accordingly, as indicated by TABLE 4, when the μθ charge pump circuit 262B is configured to operate in the 3/2 x V_BAT mode, the first switch 362, (SW 1 ), the fifth switch 370, (SW 5), and the eighth switch 376, (SW 8), are configured to be closed when the μθ charge pump circuit 262B operates in a first phase of operation, (PHASE 1 ). In addition, the second switch 364, (SW 2), the seventh switch 374, (SW 7), the eleventh switch 382, (SW 1 1 ) and the twelfth switch 384, (SW 1 2), are configured to be closed when the μθ charge pump circuit 262B operates in a second phase of operation, (PHASE 2). Otherwise, the first switch 362, (SW 1 ), the second switch 364, (SW 2), the third switch 366, (SW 3), the fourth switch 368, (SW 4), the fifth switch 370, (SW 5), the sixth switch 372, (SW 6), the seventh switch 374, (SW 7), the eighth switch 376, (SW 8), the ninth switch 378, (SW 9), the tenth switch 380, (SW 1 0), the eleventh switch 382, (SW 1 1 ), the twelfth switch 384, (SW 1 2), and the thirteenth switch 386, (SW 13), are configured to be open. As a result, the μθ charge pump output provides a μθ charge pump output voltage, ν_μ0_ουτ, substantially equal to 3/2 x VBAT when the μθ charge pump circuit 262B is configured to operate in the 3/2 x VBAT mode.

[00368] Also similar to the μθ charge pump circuit 262A, the μθ charge pump circuit 262B may be configured to operate in the 4/3 x V_BAT mode by setting the operational ratio of the μθ charge pump, μΒΒρΑτιο, to 4/3. As indicated in Table 4, similar to the operation of the μθ charge pump circuit 262A, when the operational ratio of the μθ charge pump, μΒΒρΑτιο, is set to 4/3, the μθ charge pump circuit 262B may operate in a first phase of operation, (PHASE 1 ), a second phase of operation, (PHASE 2), and third phase of operation, (PHASE 3), dependent upon the μθ charge pump clock 276.

[00369] Accordingly, as indicated by TABLE 4, when the μθ charge pump circuit 262B is configured to operate in the 4/3 x V_BAT mode, the first switch 362, (SW 1 ), the fifth switch 370 (SW 5), and the eighth switch 376, (SW 8), are configured to be closed when the μθ charge pump circuit 262B operates in a first phase of operation, (PHASE 1 ). In addition, the second switch 364 (SW 2), the sixth switch 372, (SW 6), and the thirteenth switch 386, (SW 13), are configured to be closed when the μθ charge pump circuit 262B operates in a second phase of operation, (PHASE 2). Likewise, the seventh switch 374, (SW 7), and the twelfth switch 384, (SW 12), are configured to be closed when the μθ charge pump circuit 262B operates in a third phase of operation, (PHASE 3). Otherwise, the first switch 362, (SW 1 ), the second switch 364, (SW 2), the third switch 366, (SW 3), the fourth switch 368, (SW 4), the fifth switch 370, (SW 5), the sixth switch 372, (SW 6), the seventh switch 374, (SW 7), the eighth switch 376, (SW 8), the ninth switch 378, (SW 9), the tenth switch 380, (SW 10), the eleventh switch 382, (SW 1 1 ), the twelfth switch 384, (SW 12), and the thirteenth switch 386, (SW 13), are configured to be open. As a result, the μθ charge pump output provides a μθ charge pump output voltage, V _μο_ουτ, substantially equal to 4/3 x VBAT when the μθ charge pump circuit 262B is configured to operate in the 4/3 x VBAT mode.

[00370] Also similar the μθ charge pump circuit 262A, the μθ charge pump circuit 262B may be configured to operate in the 1 x V_BAT mode by setting the operational ratio of the μθ charge pump, μΒΒρΑτιο, to 1 . As indicated in Table 4, similar to the operation of the μθ charge pump circuit 262A, when the operational ratio of the μθ charge pump, μΒΒρΑτιο, is set to 1 , the μθ charge pump circuit 262B only operates in a first phase of operation, (PHASE 1 ) because the switches are statically switched into a configuration that provides a minimum impedance between the supply voltage 24, (V_BAT), and the μθ charge pump output. In other words, when the μθ charge pump circuit 262B is configured to operate in the 1 x V_BAT mode, the switch states of the indicated switched remain in either an open state or a closed state and do not change over time. he minimum impedance is provided by selectively turning on various switches to form parallel paths between the supply voltage 24, (V_BAT), and the μθ charge pump output. Advantageously, the parallel paths lower the drop in voltage seen across the switches of the μθ charge pump circuit 262B and reduce power consumption from the battery 20. However, for the sake of consistency with the other operational modes of the μθ charge pump circuit 262B, the operation of theiC charge pump circuit 262B, the operation of the μθ charge pump circuit 262B, when configured to operate in the 1 x V_BAT mode, is described as operating only in a first phase of operation (Phase 1 ).

[00371 ] Accordingly, as indicated by TABLE 4, when the μθ charge pump circuit 262B is configured to operate in the 1 x V_BAT mode, the first switch 362, (SW 1 ), the second switch 264, (SW 2), the fourth switch 368, (SW 4), the sixth switch 372, (SW 6), the seventh switch 374, (SW 7), the ninth switch 378, (SW 9), the eleventh switch 382, (SW 1 1 ), and the twelfth switch 384, (SW 12), are configured to be closed. In addition, the third switch 366, (SW 3), the fifth switch 370, (SW 5), the eighth switch 376, (SW 8), the tenth switch 380, (SW 10), and the thirteenth switch 386, (SW 13), are configured to be open. As a result, the [iC charge pump output provides a μθ charge pump output voltage, ν_μ0_ουτ, substantially equal to 1 x V_BAT when the μθ charge pump circuit 262B is configured to operate in the 1 x V_BAT mode.

[00372] Also similar the μθ charge pump circuit 262A, the μθ charge pump circuit 262B may be configured to operate in the OFF mode by setting the operational ratio of the μθ charge pump, μΒΒρΑτιο, to OFF. When the μθ charge pump circuit 262B is configured to operate in the OFF mode, the μθ charge pump circuit 262B is disabled and the μθ charge pump output floats. As indicated by TABLE 4, when the μθ charge pump circuit 262B is configured to operate in the OFF mode, the first switch 362, (SW 1 ), the second switch 364, (SW 2), the third switch 366, (SW 3), the fourth switch 368, (SW 4), the fifth switch 370, (SW 5), the sixth switch 372, (SW 6), the seventh switch 374, (SW 7), the eighth switch 376, (SW 8), the ninth switch 378, (SW 9), the tenth switch 380, (SW 10), the eleventh switch 382, (SW 1 1 ), the twelfth switch 384, (SW 12), and the thirteenth switch 386, (SW 13), are configured to be open by the μθ charge pump control circuit 316B. Accordingly, the μθ charge pump output voltage, V_MC_OUT, at the μθ charge pump output floats with respect to ground when the μθ charge pump circuit 262B is configured to operate in the OFF mode.

[00373] Unlike the μθ charge pump circuit 262A, the μθ charge pump circuit 262B may be configured to operate in a 1 /4 x V_BAT mode, 1/3 x V_BAT mode, a 1 /2 x VBAT mode, a 2/3 x V_BAT mode,

[00374] The μθ charge pump circuit 262B may be configured to operate in the 2/3 x VBAT mode by setting the operational ratio of the μθ charge pump, μΒΒρΑτιο, to 2/3. As indicated by TABLE 4, when the μθ charge pump circuit 262B is configured to operate in the 2/3 x V_BAT mode, the first switch 362, (SW 1 ), the fourth switch 368, (SW 4), the sixth switch 372, (SW 6), and the ninth switch 378, (SW 9), are configured by the μθ charge pump control circuit 316B to be closed when the μθ charge pump circuit 262B operates in a first phase of operation, (PHASE 1 ). In addition, the μθ charge pump control circuit 316B configures the second switch 364, (SW 2), the fifth switch 370, (SW 5), and the eighth switch 376, (SW 8), to be closed when the μθ charge pump circuit 262B operates in a second phase of operation, (PHASE 2). Otherwise, the μθ charge pump control circuit 316B configures the first switch 362, (SW 1 ), the second switch 364, (SW 2), the third switch 366, (SW 3), the fourth switch 368, (SW 4), the fifth switch 370, (SW 5), the sixth switch 372, (SW 6), the seventh switch 374, (SW 7), the eighth switch 376, (SW 8), the ninth switch 378, (SW 9), the tenth switch 380, (SW 10), the eleventh switch 382, (SW 1 1 ), the twelfth switch 384, (SW 12), and the thirteenth switch 386, (SW 13), to be open. As a result, the μθ charge pump output provides a μθ charge pump output voltage, ν_μ0_ουτ, substantially equal to 2/3 x V_BAT when the μθ charge pump circuit 262B is configured to operate in the 2/3 x V_BAT mode.

[00375] The μθ charge pump circuit 262B may be configured to operate in the 1 /2 x VBAT mode by setting the operational ratio of the μθ charge pump,

BBRATIO, to 1 /2. As indicated by TABLE 4, when the μθ charge pump circuit 262B is configured to operate in the 1 /2 x V_BAT mode, the μθ charge pump control circuit 316B configures the first switch 362, (SW 1 ), the fourth switch 368, the sixth switch 372, (SW 6), and the ninth switch 378, (SW 9), to be closed when the μθ charge pump circuit 262B operates in a first phase of operation, (PHASE 1 ). In addition, the μθ charge pump control circuit 316B configures the second switch 364, (SW 2), the third switch 366, (SW 3), the seventh switch 374, (SW 7), and the eighth switch 376, (SW 8), to be closed when the μθ charge pump circuit 262B operates in a second phase of operation, (PHASE 2).

Otherwise, the μθ charge pump control circuit 316B configures the first switch 362, (SW 1 ), the second switch 364, (SW 2), the third switch 366, (SW 3), the fourth switch 368, (SW 4), the fifth switch 370, (SW 5), the sixth switch 372, (SW 6), the seventh switch 374, (SW 7), the eighth switch 376, (SW 8), the ninth switch 378, (SW 9), the tenth switch 380, (SW 10), the eleventh switch 382, (SW 1 1 ), the twelfth switch 384, (SW 12), and the thirteenth switch 386, (SW 13), to be open. As a result, the μθ charge pump output provides a μθ charge pump output voltage, V _μο_ουτ, substantially equal to 1 /2 x V_BAT when the μθ charge pump circuit 262B is configured to operate in the 1 /2 x V_BAT mode.

[00376] The μθ charge pump circuit 262B may be configured to operate in the 1 /3 x V_BAT mode by setting the operational ratio of the μθ charge pump, μΒΒρΑτιο, to 1 /3. As indicated by TABLE 4, when the μθ charge pump circuit 262B is configured to operate in the 1 /3 x V_BAT mode, the μθ charge pump control circuit 316B configures the first switch 362, (SW 1 ), the fifth switch 370, (SW 5), and the ninth switch 378, (SW 9), to be closed when the μθ charge pump circuit 262B operates in a first phase of operation, (PHASE 1 ). In addition, the the μθ charge pump control circuit 316B configures the second switch 364, (SW 2), the third switch 366, (SW 3), the seventh switch 374, (SW 7), and the eighth switch 376, (SW 8), to be closed when the μθ charge pump circuit 262B operates in a second phase of operation, (PHASE 2). Otherwise, the μθ charge pump control circuit 316B configures the first switch 362, (SW 1 ), the second switch 364, (SW 2), the third switch 366, (SW 3), the fourth switch 368, (SW 4), the fifth switch 370, (SW 5), the sixth switch 372, (SW 6), the seventh switch 374, (SW 7), the eighth switch 376, (SW 8), the ninth switch 378, (SW 9), the tenth switch 380, (SW 10), the eleventh switch 382, (SW 1 1 ), the twelfth switch 384, (SW 12), and the thirteenth switch 386, (SW 13), to be open. As a result, the μθ charge pump output provides a μθ charge pump output voltage, ν_μ0_ουτ, substantially equal to 1/3 x V_BAT when the μθ charge pump circuit 262B is configured to operate in the 1 /3 x V_BAT mode.

[00377] The μθ charge pump circuit 262B may be configured to operate in the 1 /4 x VBAT mode by setting the operational ratio of the μθ charge pump, μΒΒρΑτιο, to 1 /4. Similar to the operation of the μθ charge pump circuit 262A when the μθ charge pump circuit 262A is configured to operate in the 1 /4 x V_BAT mode, the μθ charge pump circuit 262B may include a first phase of operation, (Phase 1 ), a second phase of operation, (Phase 2), and a third phase of operation, (Phase 3). As indicated by TABLE 4, when the μθ charge pump circuit 262B is configured to operate in the 1 /4 x V_BAT mode, the μθ charge pump control circuit 316B configures the first switch 362, (SW 1 ), the fifth switch 370, (SW 5), and the ninth switch 378, (SW 9), to be closed when the μθ charge pump circuit 262B operates in a first phase of operation, (PHASE 1 ). The μθ charge pump control circuit 316B configures the seventh switch 374, (SW 7), and the eighth switch 376, (SW 8), be closed when the μθ charge pump circuit 262B operates in a second phase of operation, (PHASE 2). The μθ charge pump control circuit 316B configures the third switch 366, (SW 3), and the ninth switch 378, (SW 9), to be closed when the μθ charge pump circuit 262B operates in a third of operation, (PHASE 3). Otherwise, the μθ charge pump control circuit 316B configures the first switch 362, (SW 1 ), the second switch 364, (SW 2), the third switch 366, (SW 3), the fourth switch 368, (SW 4), the fifth switch 370, (SW 5), the sixth switch 372, (SW 6), the seventh switch 374, (SW 7), the eighth switch 376, (SW 8), the ninth switch 378, (SW 9), the tenth switch 380, (SW 10), the eleventh switch 382, (SW 1 1 ), the twelfth switch 384, (SW 12), and the thirteenth switch 386, (SW 13), to be open. As a result, the μθ charge pump output provides a μθ charge pump output voltage, V_MC_OUT, substantially equal to 1 /4 x VBAT when the μθ charge pump circuit 262B is configured to operate in the 1 /4 x VBAT mode.

[00378] Figure 21 depicts a method 500 to permit the controller 50, depicted in Figures 18A-D, to selectively configure the μθ charge pump prior to transmission of a data burst by a linear RF power amplifier. Accordingly, the description of method 500 will be done with continuing reference to Figures 18A- D.

[00379] Prior to transmission of the data burst, the pseudo-envelope follower management power system 10C-F may configure the μθ charge pump circuit 262 and VOFFSET loop circuit 41 A-B in order to provide a power amplifier supply voltage, V_Cc_, that is sufficient to power the linear RF power amplifier during the transmission of the data burst. Accordingly, prior to initiation of a transmission of data by the linear RF power amplifier, the controller 50 may determine the expected envelope characteristics of the signal to be transmitted. An example transmission of data may occur in a burst transmission time-slot. To determine the expected envelope characteristics of the signal to be

transmitted, the controller 50 may consider the impact of data rate, the bandwidth of the channel and/or the type of modulation. Example types of modulation may include, but are not limited to quadrature phase shift keys (QPSK), or quadrature amplitude modulation (QAM). Alternatively, or in addition, the controller 50 may determine and consider the peak-to-average ratio characteristic of the waveform to be generated by the power amplifier.

[00380] Based upon an expected envelope characteristic of a signal to be transmitted by a power amplifier and a battery voltage, V_BAT, the controller 50 may be configured to determine a minimum operational ratio of a μθ charge pump, UBBRATIO_MIN- (Step 502). In order to determine the minimum operational ratio of a μθ charge pump, UBB_RATIO_MIN, the controller uses the expected envelope characteristics of the signal to be transmitted to determine the expected peak to peak swing of the power amplifier supply voltage, V_Cc_ PKPK_J and obtains the voltage level of the battery, as present on the supply voltage 24, (V_BAT)- The expected peak to peak swing of the power amplifier supply voltage, V_CC_PKPK, represents the dynamic range of voltages that the controller 50 expects to be generated on the power amplifier supply voltage, V_Cc, during the transmission of data. Effectively, the expected peak to peak swing of the power amplifier supply voltage, V_CC_PKPK, equals the difference between maximum expected power amplifier supply voltage, V_CC_MAX and the minimum expected power amplifier supply voltage, V_CC_MIN, that the controller 50 expects to be generated on the power amplifier supply voltage, V_Cc, during the data transmission.

[00381 ] In addition to the expected peak to peak swing of the power amplifier supply voltage, V_Cc_ PKPK_J the controller may also take into consideration the minimum headroom voltage, VHEADROOM, of the switching elements of the parallel amplifier 35. As an example, referring to Figures 12E-F, the controller 50 may consider the minimum headroom voltage, VHEADROOM, for the first switching element, SWi_A, 214, and a second switching element, SW-|_B, 216. In addition, in some embodiments, the controller 50 may consider the minimum headroom for each of the switching devices (SW _A, 214 and SW _B, 216) individually. As an example, for the case where the first switching element, SW _A, 214 is a PFET device, the controller 50 may use the minimum PFET headroom voltage,

VHEADROOM_P, to determine the operational ratio of a μθ charge pump, UBBRATIO- In the case where the second switching element, SW _B, 216 is an NFET device, the controller 50 may use the minimum NFET headroom voltage, V_HEADROOM_N to determine the operational ratio of a μθ charge pump, UBBRATIO-

[00382] Accordingly, in the general case, the controller 50 may determine the minimum operational ratio of a μθ charge pump, UBB_RATIO_MIN_, as follows:

(1 ) UBBRATIO_MIN = [ VCC_PKPK + VHEADROOM_N + VHEADROOM_P )/V_BAT [00383] Based on the minimum operational ratio of the μθ charge pump, UBBRATIO_MIN, the controller 50 may be configured to select an operational ratio of the iC charge pump, UBBRATIO, that is greater than the minimum operational ratio of the [iC charge pump, UBB_RATIO_MIN. (Step 504). As indicated by Tables 1 and 3, the available values of operational ratios of the μθ charge pump, UBBRATIO, depend upon the embodiment of the μθ charge pump circuit 262. As an example, the embodiment of the μθ charge pump circuit 262A, depicted in Figure 19A, provides several modes of operation where each mode of operation is associated with an operational ratio of the μθ charge pump, UBBRATIO, as shown in Table 1 . Likewise, the example embodiment of the μθ charge pump circuit 262B, depicted in Figure 19B, provides a number of modes of operation where each mode of operation is associated with an operational ratio of the μθ charge pump, UBBRATIO, as shown in Table 3. Depending upon the calculated value of the minimum operational ratio of a μθ charge pump, UBB_RATIO_MIN, the controller 50 initially selects the smallest available operational ratio of the μθ charge pump, UBBRATIO, of the [iC charge pump circuit 262 that is greater than the minimum operational ratio of a μθ charge pump, UBB_RATIO_MIN- AS an example, in the case where the μθ charge pump circuit 262 is similar to the μθ charge pump circuit 262B of Figure 19B (Table 3), if the minimum operational ratio of a μθ charge pump, UBBRATIO_MIN, is greater than 1 /4 but less than 1 /3, the controller initially selects the operational ratio of the μθ charge pump, UBBRATIO, to be 1 /3.

[00384] Thereafter, the controller may be configured to calculate an expected value for an offset voltage, VOFFSET, to be generated across a coupling device, V₀FFSET_EXPECTED, based upon the operational ratio of the μθ charge pump, UBBRATIO, of the μθ charge pump, selected by the controller 50 (Step 506). The expected value for an offset voltage, V₀FFSET_EXPECTED, may be calculated as follows:

(2) VOFFSET_EXPECTED = VCC_PKPK - VBAT X UBBRATIO + VHEADROOM_P [00385] Thereafter, the controller 50 may be configured to determine whether the expected value for the offset voltage, V₀FFSET_ EXPECTED_J to be generated across the coupling device is greater than zero, V₀FFSET_EXPECTED, > 0. (Step 508). In some alternative embodiments of method 500, the controller 50 may determine whether the expected value for the offset voltage,

VOFFSET_EXPECTED, to be generated across the coupling device is greater than a minimum offset voltage, V₀FFSET_MIN, where the minimum offset voltage,

VOFFSET_MIN, is a configurable parameter. In this example embodiment of method 500, it will be understood that the minimum offset voltage, V₀FFSET_MIN, is zero.

[00386] If the expected value for the offset voltage, VOFFSET, to be generated across the coupling device is less than zero, V₀FFSET_EXPECTED, < 0, the controller 50 increments the value of the operational ratio of the μθ charge pump,

UBBRATIO, to the next highest value of operational ratio of the μθ charge pump, UBBRATIO, available for the μθ charge pump circuit 262. (Step 51 0). For example, in the case where the μθ charge pump circuit 262 is similar to the μθ charge pump circuit 262B of Figure 1 9B, if the initially determined value of the operational ratio of the μθ charge pump, UBBRATIO, of the μθ charge pump circuit 262B is 1 /3, the controller 50 will increment the value of the operational ratio of the iC charge pump, UBBRATIO, to 1 /2. Thereafter, method 500 returns to Step 508 to recalculate the expected value for an offset voltage, V₀FFSET_EXPECTED, using the new value of the operational ratio of the μθ charge pump, UBBRATIO, This process continues until the controller 50 identifies the minimum value of the operational ratio of the μθ charge pump, UBBRATIO, of the μθ charge pump circuit 262 for which V₀FFSET_EXPECTED, > 0.

[00387] After identifying the minimum value of the operational ratio of the [iC charge pump, UBBRATIO, of the μθ charge pump circuit 262 for which

VOFFSET_EXPECTED, > 0, the controller selects the operational ratio of the μθ charge pump, UBBRATIO, as a selected operational ratio of a μθ charge pump,

UBBRATIO_SEL, to be used during the transmission of data by the linear RF power amplifier. (Step 51 2). Via the μθ charge pump control bus 278, the controller 50 configures the μθ charge pump circuit 262 to generate a μθ charge pump output voltage, ν_μ0_ουτ, on the μθ charge pump output based upon the selected operational ratio of a μθ charge pump, UBB_RATIO_SEL- (Step 514).

[00388] Thereafter, in some embodiments of method 500, the controller 50 configures the VOFFSET LOOP Circuit 41 A-B to generate an offset voltage, VOFFSET, substantially equal to an expected value for the target offset voltage,

VOFFSET_EXPECTED, when the μθ charge pump circuit 262 uses the selected operational ratio of a μθ charge pump, UBB_RATIO_SEL- (Step 516). Accordingly, the controller 50 may be configured to calculate the value of an expected target offset voltage, V₀FFSET_TARGET_EXPECTED, when the μθ charge pump circuit 262 is configured to operate using the selected operational ratio of a μθ charge pump, UBBRATIO_SEL- The value of the target offset voltage, V_OFFSET_TARGET_EXPECTED, may be calculated as follows:

(3) VoFFSET_TARGET_EXPECTED = Vcc_PKPK ~ VBAT X UBBRATIO_SEL + VHEADROOM_P

Thereafter, the controller 50 may be configure to use the value of the value of the expected target offset voltage, VOFFSET TARGET EXPECTED_J to determine the parameter value of VOFFSET TARGET to be provided to the VOFFSET loop circuit 41 A- B. Via the μθ charge pump control bus 278, the controller 50 provides the

VOFFSET TARGET parameter to the VOFFSET loop circuit 41 A-B.

[00389] A method 600, depicted in Figure 22, is described with continuing reference Figures 18B and 18D. The method 600 provides for the configuration of a VOFFSET Loop Circuit 41 B, depicted in Figures 18B and 18D, to minimize a pre-charging time period of the coupling circuit 18 to a desired offset voltage, VOFFSET, prior to commencing a transmission, by the linear RF power amplifier 22 (Figure 1 A-B) of a data burst in a the transmission-slot. As an example, prior to commencing the transmission of the data burst, the controller 50 may determine whether a coupling circuit 18 coupled between a parallel amplifier output 32A and a power amplifier supply voltage, V_Cc, requires pre-charging prior to initiation of the transmission by a radio frequency power amplifier, (Step 602). Illustratively, the controller 50 may determine whether a data burst to be transmitted is a first data burst of a transmission of data by the linear RF power amplifier 22. If the data burst to be transmitted is a first data burst of the transmission, the controller 50 may determine that the coupling circuit 18 requires pre-charging prior to transmission of the first data burst.

[00390] Alternatively, the controller 50 may determine whether the coupling circuit 18 requires pre-charging based upon the VOFFSET loop error 304 generated by the summing circuit 300. As an example, the controller 50 may set the value of the VOFFSET TARGET parameter for the VOFFSET Loop Circuit 41 B. Thereafter, the controller 50 may obtain the VOFFSET loop error 304 from the VOFFSET Loop Circuit 41 B via the VOFFSET control bus 312. If the VOFFSET loop error 304 is greater than a maximum VOFFSET error threshold parameter, the controller 50 determines that the power amplifier supply voltage, V_Cc, requires pre-charging prior to initiation of transmission of the first burst.

[00391 ] In response to the determination that the coupling circuit between the parallel amplifier and the power amplifier supply voltage, V_Cc, requires pre- charging, the controller 50 may configure the VOFFSET loop circuit 41 B such that the VOFFSET loop circuit 41 B operates in first bandwidth mode, where the first bandwidth mode increases the operable bandwidth of the VOFFSET loop circuit 41 B. (Step 604).

[00392] As discussed relative to the description of Figures 18B and 18D, the integrator with zero compensation 314 may include a first time constant, Tauo, and a second time constant, Tau-i. During normal operation of the VOFFSET loop circuit 41 B, the values of the first time constant, Tau₀, and a second time constant, Tau-i, may be configured to optimize regulation of the offset voltage, VOFFSET, that is developed across the coupling device 18. For example, the controller 50 may configure the VOFFSET loop circuit 41 B to operate with a normal frequency bandwidth. Illustratively, to configure the VOFFSET loop circuit 41 B to operate with a normal frequency bandwidth, the controller 50 may configure the first time constant, Tau₀, to be equal to Tau₀_normal and the second time constant, Taui, to be equal to Taui_normal. In some embodiments of the VOFFSET loop circuit 41 B, the values of time constants Tau₀_normal and

Tau-i_normal, may be stored locally with the VOFFSET loop circuit 41 B.

[00393] To decrease the time for pre-charging the coupling circuit 18, the controller may configure the first time constant, Tau₀, to be equal to a first startup time constant, Tau₀_startup, and the second time constant, Tau-i , to be equal to a second startup time constant, Taui_startup. Alternatively, some embodiments of the VOFFSET loop circuit 41 B be configured to automatically set the first time constant, Tau₀, equal to the first startup time constant, Tau₀_startup, and the second time constant, Tau-i , when the VOFFSET loop circuit 41 B is placed in a pre- charge mode of operation.

[00394] In some embodiments of method 600, the controller 50 may configure the VOFFSET loop circuit 41 B to initially operate using the first startup time constant, Tau₀_startup, and the second startup time constant, Taui_startup, by configuring the VOFFSET loop circuit 41 B operate in the pre-charge mode of operation for a period of time. As an example, in some embodiments of the

VOFFSET loop circuit 41 B, the period of time in which the VOFFSET loop circuit 41 B operates in a pre-charge mode of operation may be configured by the controller 50 via the VOFFSET control bus 312. In some embodiments of the VOFFSET loop circuit 41 B, the period of time in which the VOFFSET loop circuit 41 B operates in a pre-charge mode of operation is a predetermined time period that may be configured by the controller 50 via VOFFSET control bus 312. As an example, VOFFSET loop circuit 41 B may include a pre-charge timer (not shown) that may be set to trigger a timer event after the predetermined time period.

[00395] Once the coupling circuit 18 is pre-charged, the VOFFSET loop circuit 41 B may be placed into a normal mode of operation. As an example, after a predetermined time period, the VOFFSET loop circuit 41 B may be re-configured such that the VOFFSET loop circuit operates 41 B in a second bandwidth mode, where the second bandwidth mode decreases the operable bandwidth of the VOFFSET loop circuit 41 B. (Step 606). Accordingly, the bandwidth of the VOFFSET loop circuit 41 B that operates in the first bandwidth mode is greater than the bandwidth of the VOFFSET loop circuit 41 B that operates in the second bandwidth mode.

[00396] As an example, in order to place the VOFFSET loop circuit 41 B into the second bandwidth mode for normal operation during transmission of data by the power amplifier 22, the controller 50 may configure the first time constant, Tauo, to be equal to Tau₀_normal and the second time constant, Tau-i , to be equal to Tau-i_normal via the VOFFSET control bus 312. Alternatively, as an example, VOFFSET loop circuit 41 B may automatically switch from the pre-charge mode of operation to a normal mode of operation upon triggering of the timer event by the pre-charge timer.

[00397] Those skilled in the art will recognize improvements and

modifications to the embodiments of the present disclosure. All such

improvements and modifications are considered within the scope of the concepts disclosed herein and the claims that follow.

Claims

Claims What is claimed is:

1 . A power management system for a linear radio frequency power amplifier comprising:

a charge pump including a first flying capacitor, a second flying capacitor, a plurality of switches operably coupled to form a charge pump parallel amplifier power supply output, wherein the charge pump is configured to selectively generate a selected output voltage level of a plurality of output voltage levels, derived from a first supply voltage, on the charge pump parallel amplifier power supply output of the charge pump based upon a selected charge pump operational mode of a plurality of charge pump operational modes;

a switch mode power supply converter including a plurality of switching operational modes configured to generate a plurality of switching voltage levels on a switching voltage output, wherein the switching voltage output is coupled to a capacitor via a power inductor to form a linear radio frequency power amplifier supply output configured to power the linear radio frequency power amplifier; and a parallel amplifier including a parallel amplifier output in communication with the linear radio frequency power amplifier supply output and a parallel amplifier supply input in communication with the charge pump parallel amplifier power supply output, wherein at least a portion of the parallel amplifier is configured to be powered from the charge pump parallel amplifier power supply output.

2. The power management system of claim 1 , wherein in at least one of the plurality of charge pump operational modes the charge pump is further configured to boost the first supply voltage to generate the selected output voltage level such that the selected output voltage level is greater than the first supply voltage.

3. The power management system of claim 1 wherein in at least one of the plurality of charge pump operational modes, the charge pump is further configured to buck the first supply voltage to generate the selected output voltage level such that the selected output voltage level is less than the first supply voltage.

4. The power management system of claim 1 , wherein in at least one of the plurality of charge pump operational modes, the charge pump is further configured to generate the selected output voltage level such that the selected output voltage level is substantially equal to the first supply voltage.

5. The power management system of claim 1 , wherein the plurality of charge pump operational modes includes at least one of a first operational mode and a second operational mode, wherein the charge pump is configured to generate the selected output voltage level such that the selected output voltage level is substantially equal to 4/3 x the first supply voltage in the first operational mode, and the charge pump is configured to generate the selected output voltage level such that the selected output voltage level is substantially equal to 4/3 x the first supply voltage in the second operational mode.

6. The power management system of claim 5, wherein the plurality of charge pump operational modes further includes at least one of a third operational mode, a fourth operational mode, a fifth operational mode, and a sixth

operational mode, wherein the charge pump is configured to generate the selected output voltage level such that the selected output voltage level is substantially equal to 3/2 x the first supply voltage in the third operational mode, the charge pump is configured to generate the selected output voltage level such that the selected output voltage level is substantially equal to 1 /2 x the first supply voltage in the fourth operational mode, the charge pump is configured to generate the selected output voltage level such that the selected output voltage level is substantially equal to 1 /3 x the first supply voltage in the fifth operational mode, and the charge pump is configured to generate the selected output voltage level such that the selected output voltage level is substantially equal to 1 /4 x the first supply voltage in the sixth operational mode,

7. The power management system of claim 1 , wherein the switch mode power supply converter further includes a multi-level charge pump configured to generate at least one of a plurality of charge pump voltage levels derived from the first supply voltage at a charge pump output; and

wherein in at least one of the plurality of switching operational modes of the switch mode power supply converter, the switch mode power supply converter is configured to provide the at least one of a plurality of charge pump voltage levels generated by the multi-level charge pump as a switching voltage level of the plurality of switching voltage levels on the switching voltage output.

8. The power management system of claim 7, wherein the multi-level charge pump includes a third flying capacitor, a fourth flying capacitor, and a plurality of charge pump switches operably configured to form charge pump output.

9. The power management system of claim 7, wherein the multi-level charge pump further includes an internal switch operably coupled to one of the first flying capacitor and the second flying capacitor, and wherein the multi-level charge pump is further configured to control the internal switch to generate a multi-level charge pump parallel amplifier power supply output, wherein the multi-level charge pump parallel amplifier power supply output is in communication with the parallel amplifier supply input; and

wherein the parallel amplifier is further configured to be selectively powered by one of the multi-level charge pump parallel amplifier power supply output and the charge pump parallel amplifier power supply output.