WO2009065050A1

WO2009065050A1 - Data-dependet voltage regulator

Info

Publication number: WO2009065050A1
Application number: PCT/US2008/083655
Authority: WO
Inventors: Yohan Frans; Brian Leibowitz; Nhat Nguyen
Original assignee: Rambus Inc.
Priority date: 2007-11-15
Filing date: 2008-11-14
Publication date: 2009-05-22

Abstract

A data-dependent voltage regulator maintains a relatively stable voltage in the presence of data-induced supply-current fluctuations. The regulator includes a feedback path through a replica load that provides a data-dependent replica voltage for fast feedback. The regulator reduces data-dependent supply- voltage fluctuations on a regulated voltage without resorting to a compensation current.

Description

DATA-DEPENDENT VOLTAGE REGULATOR

Yohan Frans

Brian Leibowitz

Nhat Nguyen

FIELD

[0001] The subject matter disclosed herein relates generally to voltage regulators, and more particularly to voltage regulators that are relatively insensitive to load fluctuations.

BACKGROUND

[0002] Power supplies provide voltage and current to power electronic devices. An ideal power supply can provide a constant voltage over a range of current levels to satisfy varying load requirements. In practice, however, changing load currents induce supply- voltage fluctuations that can induce errors in sensitive circuits. The task of minimizing supply- voltage fluctuations is typically done by an electronic circuit known as a "voltage regulator." [0003] Typical voltage regulators identify errors in their regulated output voltage by comparing the regulated voltage to a reference voltage. Using what engineers refer to as a "negative feedback servo control loop," the difference between the regulated and reference voltages is sensed and used to adjust the regulated supply closer to reference voltage. The control loop must be carefully designed to produce a desired tradeoff between the stability of the regulated voltage and the speed with which the regulator counteracts errors. [0004] Voltage regulators are commonly used in sensitive circuits that transmit, receive, or otherwise manipulate data. When the data is represented as changing sequences of symbols, or symbol patterns, the current required to express changing symbol patterns varies with the patterns. The current drawn from a voltage regulator can therefore fluctuate with the data (i.e., the supply current is "data-dependent"). Power supplies and the wires they use to supply current exhibit impedances to the supply current. Drawing the data-dependent supply current through these non-zero impedances causes the regulated voltage to exhibit a data- dependent component (i.e., the regulated voltage is data-dependent). [0005] The data dependent fluctuation of the regulated voltage is undesirable. In an input/output circuit such as transmitter/receiver circuit, it may cause a timing shift in the transmitted and/or received data. In a data-processing circuit, it may cause data errors. Efforts are therefore made to minimize data-dependent fluctuation of the regulated voltage, such as by reducing supply-related impedances. Another technique reduces supply-dependent current fluctuations by adding a data-dependent compensation current to the data-dependent load current. The compensation current - with magnitude similar to the load current - complements the load current so that the sum of the compensation and load currents is relatively constant. Because the supply current is relatively constant, so too is the regulated voltage. [0006] Data-dependent compensation currents work well to reduce data-dependent voltage fluctuations. This advantage comes with a cost, however: directly adding the compensation current with similar magnitude as load current wastes power especially when the peak load current is significantly larger than the average load current (e.g., roughly twice as large). There is therefore a need for more efficient methods and circuits for reducing data- dependent supply-voltage fluctuations.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The subject matter disclosed is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which: [0008] Figure IA details a power-efficient voltage regulator 100, in accordance with one embodiment, that supplies a regulated voltage Vreg to a data-dependent load 103.

[0009] Figure IB is a flowchart 120 outlining the operation of voltage regulator 100 of

Figure IA in accordance with one embodiment.

[0010] Figure 2 depicts first and second integrated circuits (ICs) 200 and 205, the first of which includes a data-dependent voltage regulator that maintains a relatively stable voltage in the presence of supply-current fluctuations.

[0011] Figure 3 details an embodiment of the data-dependent voltage regulator of Figure

2.

DETAILED DESCRIPTION

[0012] Figure IA details a power-efficient voltage regulator 100, in accordance with one embodiment, that supplies a regulated voltage Vreg to a data-dependent load 103. Regulator

100 reduces data-dependent supply- voltage fluctuations on voltage Vreg without resorting to a compensation current, and thus saves power.

[0013] Regulator 100 includes a replica load 105 that replicates the data-dependent behavior of load 103. A first transistor 107 coupled between supply node VTT and regulator output node Vreg defines a regulated- voltage current path. A second transistor 110 coupled between supply node VTT and replica- voltage node Vrep defines a replica- voltage current path. Currents Ireg and Irep through respective transistors 107 and 110 change as their respective loads 105 and 103 respond to changes in input signal Data. The data-dependent changes in the regulated and replica currents Ireg and Irep induce data-dependent changes in the regulated and replica voltages Vreg and Vrep.

[0014] An error amplifier 115 supports two feedback paths, a slow path from transistor

107 and a fast path from transistor 110. As detailed below, error amplifier 115 controls the gate voltages of transistors 107 and 110 responsive to changes in the regulated and replica voltages Vreg and Vrep to oppose those changes. Amplifier 115, transistors 107 and 110, and the fast and slow feedback paths form two negative feedback servo loops that together maintain the regulated voltage Vreg at reference voltage Vref. Replica load 105 provides fast feedback to the error amplifier through data-dependent fluctuations on voltage Vrep, and thus helps suppress voltage fluctuations on the regulator output node Vreg due to data dependent load current variations.

[0015] Load 103 can be e.g. a transmitter, receiver, or digital-to-analog converter that communicates data signal Data. Signal Data is also conveyed to replica load 105, the internal circuitry of which is designed to emulate the loading behavior (relationships between supply- current and supply- voltage, and between supply-current and data activity) of load 103, albeit at a significantly lower current (i.e., replica current Irep is much smaller than regulated current Ireg). As a consequence, replica voltage Vrep exhibits data-dependent voltage fluctuations that are scaled to match undesired voltage fluctuation on regulated voltage Vreg. [0016] Error amplifier 115 amplifies the voltage fluctuations on node Vreg and the scaled voltage fluctuation on replica voltage Vrep and feeds the amplified results Vfb to transistors 107 and 110 to control regulated voltage Vreg and replica voltage Vrep. The current path through transistor 107 has a capacitive load 117 that has low-pass response, and consequently rejects high-frequency noise from external supply (VTT) and/or load-current. Capacitive load 117 can be part of load 103 or can be provided or supplemented using separate components. Capacitive load 117 stabilizes voltage Vreg by slowing the response of node Vreg to Io w- frequency and mid-frequency disturbances on the external supply and/or load-current. Node Vrep has far less capacitive loading, and consequently exhibits a much faster response to low-frequency and mid-frequency disturbances. [0017] Error amplifier 115 senses differences between regulated voltage Vrep and reference-voltage Vref and adjusts the current through transistor 110 to counter the difference by changing control voltage Vfb. The changes to node Vrep are dependent upon the same data signal as those on node Vreg, so the replica- voltage fluctuations replicate those of the regulator output voltage. The lower capacitance of the fast feedback path through transistor 110 allows node Vrep to respond to load changes more quickly than node Vreg, so error amplifier 115 quickly counteracts voltage fluctuations on nodes Vreg and Vrep. Current Irep through the replica path can be scaled much lower than load current Ireg, and is about one eight the current in one embodiment. The size of the replica load and the fast control loop through transistor 110 should be carefully designed to produce a desired tradeoff between stability and speed of response.

[0018] Figure IB is a flowchart 120 outlining the operation of voltage regulator 100 of Figure IA in accordance with one embodiment. Other data-dependent regulators can perform the same or similar steps using different circuitry. Starting at step 125, data is applied to node Data with reference and supply voltages applied to node Vref and VTT, respectively (Figure IA). Responsive to the data, load 103 and replica load 105 draw data-dependent supply currents Ireg and Irep from node VTT (step 130), and thus induce data-dependent errors in voltages Vreg and Vrep. Error amplifier 115 compares replica voltage Vrep and supply voltage Vreg to reference voltage Vref (step 135). Error amplifier 115, by controlling feedback voltage Vfb, then adjusts currents Ireg and Irep responsive to the voltage comparison (step 140) to counteract the errors in voltages Vreg and Vrep. The steps of flowchart 120 are drawn separately for ease of illustration, but the depicted embodiment performs the operations contemporaneously in a servo loop. [0019] Figure 2 depicts first and second integrated circuits (ICs) 200 and 205 interconnected via a differential, bidirectional interface 210. The first and second ICs might be e.g. a memory device and memory controller in a high-performance memory system. One or both ICs include communication circuitry that transmits or receives data with the aid of a data-dependent voltage regulator similar to regulator 100 of Figure IA, but adapted to respond to data TxS[3:0] and RxD[3:0] received by respective communication circuits hi synchronization with clock signals I&Q. Regulator 270 maintains a relatively stable voltage Vreg in the presence of data-dependent supply-current fluctuations without resorting to the use of a compensation current, and thus saves power.

[0020] Figure 2 shows the first IC 200 as a top-level architectural view of a 16-Gb/s differential, bidirectional input/output (I/O) transceiver cell in an emulated 40nm DRAM process that has a fan-out-of-four inverter delay (FO4) of 45ps, resulting in a bit time that is only 1.4 FO4 delays long. The transceiver of IC 200 exhibits random jitter of 380fs rms at the transmitter output and a bit-error rate (BER) of less then 10E- 14 while consuming just 8mW/Gb/s. The transceiver implements several techniques to achieve low jitter despite the slow process and constrained power consumption, including quad-rate clocking with closed- loop quadrature correction, a shared LC-PLL with octagonal inductor (not shown) in a three- metal process, and a data-dependent voltage regulator. The last of these is the focus of the appended claims, and is thus described in detail.

[0021] Second IC 205 supports bidirectional communication over channel 210 with a receiver 211 and transmitter 212. This IC is a generic device in this example, and may include e.g. memory controller or other logic that uses the transmitter and receiver to communicate with IC 200. For example, first IC 200 may additionally include one or more memory arrays and second IC 205 memory-controller logic. Such circuits are omitted for brevity. First IC 200 will alternatively be referred to as the "transceiver" 200 because all of the depicted components are transceiver components. [0022] Transceiver 200 uses a quad-rate clocking scheme to circumvent high gate delay (FO4), a quadrature corrector to minimize phase error in the I&Q clocks, an LC-PLL to achieve low random jitter, a data-dependent regulator to minimize power-supply-induced jitter in the data paths, and current-mode logic (CML) signaling to minimize power-supply- induced jitter in the clock path. The depicted embodiment of transceiver 200 is implemented in a 65nm process with design restrictions to emulate a projected 40nm DRAM process. [0023] On the transmit side, transceiver 200 includes a multiplexer 215, a transmit pulser 220, and a transmit-driver 225. In one embodiment pulser 220 is implemented using CMOS NAND gates instead of e.g. CML multiplexers to achieve faster performance and lower power consumption. The differential outputs from transmit-driver 225 are coupled to supply node VTT via a pair of termination resistors Rt and to channel 210 via pads 227. In operation, multiplexer 215 converts parallel 32-bit data Tx[31 :0] into 4-bit data TxS[3:0]. The clock signals I&Q/8 to multiplexer 215 are divided versions of clock signals I&Q used to time data transmission and reception. Pulser 220 converts the 4-bit data TxS[3:0] into four pulse trains TX[3:0] on a like-named bus to transmit-driver 225. Finally, transmit-driver 225 uses a pre- driver 230 and subsequent driver 235 to convert the four pulse trains into a sequence of data symbols represented using complementary voltages. The communication circuitry employed to transmit data is conventional, so a detailed discussion is omitted for brevity. [0024] On the receive side, transceiver 200 includes a linear equalizer 240, a set of four samplers 245 with offset cancellation (not shown), and a 4:32 demultiplexer 250. Equalizer 240 equalizes differential data symbols received on pads 227 from IC 205 and presents the resulting equalized differential signal RxP/RxN to samplers 245. Samplers 245 sample the differential signals on four clock phases to provide four-bit parallel data RxD[3:0], which demultiplexer 250 converts to 32-bit data Rx[31 :0]. hi one embodiment samplers 245 employ CMOS-style StrongARM sense amplifiers, rather than CML latches, to achieve faster regeneration and reset performance with lower power consumption. As with the transmit side, the communication circuitry employed to receive data is conventional. [0025] Timing for the communication circuitry of transceiver 200 is provided by an LC- PLL 255, a level converter 260, and a quadrature corrector 265. An LC-PLL is a phase- locked loop (PLL) that uses an LC circuit to define its resonant frequency. LC-PLL 255 contains, in this example, an 8-GHz LC-VCO (not shown) followed by a quadrature divide- by-two circuit to generate four 4GHz quadrature clocks CML[3:0] from a 500MHz reference clock RefClk. Converter 260 converts the CML quadrature clocks to CMOS levels and provides the resulting clock signals to quadrature corrector 265, which correct quadrature errors by adjusting switched-capacitor clock loads (not shown). The corrected quadrature clock signals I&Q are distributed to various of the communication circuits. Other manners of establishing timing might also be used, as will be evident to those of skill in the art. The outline of one manner of synchronizing transmit and receive elements is provided here for context.

[0026] The CMOS circuits within pulser 220, samplers 245, quadrature corrector 265, and converter 260 are sensitive to supply-voltage fluctuations. For example, supply-voltage fluctuations in the pulser 220 will directly affect timing of data transmitted by IC 200 to the channel. In addition to being sensitive to supply- voltage fluctuations, pulser 220 and samplers 245 also cause large variations in supply-current as they convey changing data patterns on their respective input ports to their respective output ports. Pulser 220 and samplers 245 thus modulate their respective supply currents and, as a consequence, their regulated supply voltage Vreg. Transceiver 200 addresses this problem with a data-dependent regulator 270 that develops regulated voltage Vreg from a reference voltage Vref, a supply voltage VTT, and data TxS[3:0] and RxD[3:0] from the transmit and receive sections of the transceiver. Regulator 270 stabilizes regulated voltage Vreg while allowing supply current Itt to change with the data patterns. Regulator 270 thus reduces the average power consumption as compared with introducing compensation currents to minimize data-dependent supply-current fluctuations.

[0027] Figure 3 details an embodiment of data-dependent regulator 270 of Figure 2. Regulator 270 includes a replica load 300 supplied with a replica voltage Vrep, a first transistor 305 coupled between supply node VTT and regulator output node Vreg to define a regulated- voltage current path, a second transistor 310 coupled between supply node VTT and replica- voltage node Vrep to define a replica- voltage current path, and an error amplifier 315 supporting two feedback paths, a slow path from transistor 305 and a fast path from transistor 310. As detailed below, error amplifier 315 controls the gate voltages of transistors 305 and 310, and consequently the voltages Vreg and Vrep, to maintain regulated voltage Vreg equal to reference voltage Vref.

[0028] E. Alon et al. describe a voltage regulator with a replica load that achieved power- and area-efficient suppression of transient noise from an external power supply (E. Alon et al., "Replica Compensated Linear Regulators for Supply-Regulated Phase-Locked Loops," IEEE JSSC, Vol. 41, February 2006, pp. 413-424). Voltage regulator 270 extends this idea using data-dependent replica load 300 to suppress transient noise from data dependent load current variations. Each of differential clock signals I&Q, data RxD[3:0], and TxS [3:0] is conveyed to a series of CMOS inverters whose dimensions are selected to replicate the loading behavior (relationships between supply-current and supply- voltage, and between supply-current and data activity) of the CMOS communication and clocking circuitry of transceiver 200 of Figure 2. As a consequence, replica voltage Vrep exhibits data-dependent voltage fluctuations that are scaled to match the problematic voltage fluctuation on voltage Vreg. The scaled voltage fluctuation on replica voltage Vrep is amplified by error amplifier 315 and fed back to transistors 305 and 310 to control regulated voltage Vreg. The current path through transistor 305 includes a capacitor 320 to stabilize the loop and to reject high- frequency noise from external supply (VTT) and/or load-current. However, capacitor 320 also slows the response of node Vreg from low-frequency and mid-frequency disturbances on the external supply and/or load-current. This limitation does not apply to node Vrep as it does not have an explicit capacitor.

[0029] Error amplifier 315 senses differences between regulated voltage Vreg and reference- voltage Vref and adjusts the current through transistor 305 to counter the difference. Error amplifier 315 also senses differences between replica voltage Vrep and reference voltage Vref, and such differences are likewise used to adjust the current though transistor 305. The changes to node Vrep are dependent upon the same data and clock signals and those on node Vreg, so the replica- voltage fluctuations replicate those of the reference voltage. The lower capacitance of the fast feedback path allows node Vrep to respond to load changes more quickly than node Vreg, however, so error amplifier 315 can quickly counteract voltage fluctuations. Current Irep through the replica path can be scaled much lower than load current Ireg, and is about one eighth the current in one embodiment. The size of the replica load and the fast and slow control loops should be carefully designed to produce a desired tradeoff between stability and speed of response. [0030] Returning to Figure 2, the received signal RxD [3:0] is sampled by samplers 245 before it is applied to regulator 270. Because the samplers 245 generate fluctuations on Vreg, the sensed fluctuations of replica voltage Vrep (Figure 3) thus lag those of regulated voltage Vreg. This lag, approximately one unit interval, is considerably shorter than the response of voltage regulator 270, however, so the delayed application of the data-dependent correction has little impact on regulator performance.

[0031] In CMOS circuits, load currents may vary between zero (static data, either all zeros or all ones) to maximum (always toggling data like 01010101 .τ.-pattern, or a clock signal). Using compensation current Icomp to complement the data-dependent load current, the total supply current (Itt=Iload+Icomp) would be the same for each data pattern, but would be at least has high as the maximum load current Imax (Itt≥Imax).

[0032] Now consider voltage regulator 270 of Figure 3 using the same assumptions, and assuming that replica load 300 is scaled so that replica current Irep is about 1/8* the regulated current Ireg. In that case the total current Itt would vary between about zero (static data) and Imax+0.125Imax (toggling data). Assuming an even distribution of the data pattern, the average current would be approximately 56% of Imax (Itt~0.56Imax). The communication circuits that rely upon voltage regulator 270 thus draws about 44% less current, and consequently consume about 44% less power, as a similar circuits relying upon additional data-dependent current to compensate for a data-dependent load current. [0033] This forgoing example is illustrative. Other coding schemes will be impacted differently, and the simple example ignores the impact of clock signals I&Q on the regulated and replica currents.

[0034] In the foregoing description and in the accompanying drawings, specific terminology and drawing symbols are set forth to provide a thorough understanding of the present invention. In some instances, the terminology and symbols may imply specific details that are not required to practice the invention. For example, the interconnection between circuit elements or circuit blocks may be shown or described as multi-conductor or single conductor signal lines. Each of the multi-conductor signal lines may alternatively be single-conductor signal lines, and each of the single-conductor signal lines may alternatively be multi-conductor signal lines. Signals and signaling paths shown or described as being single-ended may also be differential, and vice- versa. Similarly, signals described or depicted as having active-high or active-low logic levels may have opposite logic levels in alternative embodiments. - _ — -— ^~ [0035] An output of a process for designing an integrated circuit, or a portion of an integrated circuit, comprising one or more of the circuits described herein may be a computer-readable medium such as, for example, a magnetic tape or an optical or magnetic disk. The computer-readable medium may be encoded with data structures or other information describing circuitry that may be physically instantiated as an integrated circuit or portion of an integrated circuit. Although various formats may be used for such encoding, these data structures are commonly written in Caltech Intermediate Format (CIF), Calma GDS II Stream Format (GDSII), or Electronic Design Interchange Format (EDIF). Those of skill in the art of integrated circuit design can develop such data structures from schematic diagrams of the type detailed above and the corresponding descriptions and encode the data structures on computer readable medium. Those of skill in the art of integrated circuit fabrication can use such encoded data to fabricate integrated circuits comprising one or more of the circuits described herein.

[0036] The present invention has been described in connection with specific embodiments, but is not so limited. Other embodiments will be obvious to those of ordinary skill in the art. Moreover, some components are shown directly connected to one another while others are shown connected via intermediate components. In each instance the method of interconnection, or "coupling," establishes some desired electrical communication between two or more circuit nodes, or terminals. Such coupling may often be accomplished using a number of circuit configurations, as will be understood by those of skill in the art. Therefore, the spirit and scope of the appended claims should not be limited to the foregoing description. Only those claims specifically reciting "means for" or "step for" should be construed in the manner required under the sixth paragraph of 35 U.S.C. §112.

Claims

CLAIMSWhat is claimed is:

1. A voltage regulator comprising: a power-supply node to receive a supply voltage and a supply current; a regulated-supply node to a provide a regulated supply voltage; a data port to receive data; a regulated-voltage current path between the power-supply node and the regulated-supply node to convey the regulated supply voltage; a replica- voltage current path extending from the power-supply node to convey a replica voltage; a replica load having a replica data port connected to the data port to receive the data, a replica supply node connected to the replica- voltage current path to receive the replica voltage, the replica load to draw a data-dependent replica current from the replica supply node and to modulate the replica current using the data; and a feedback path between the replica supply node and the regulated- voltage current path, the feedback path to control the regulated-supply current responsive to data-dependent changes to the replica voltage.

2. The voltage regulator of claim 1 , further comprising a second feedback path between the regulated-supply node and the regulated- voltage current path.

3. The voltage regulator of claim 2, wherein the second feedback path exhibits a slow response relative to the first-mentioned feedback path.

4. The voltage regulator of claim 1 , wherein the replica load further includes a clock port to receive a clock signal.

5. The voltage regulator of claim 1 , wherein the feedback path also extends between the replica supply node and the replica- voltage current path.

6. A method of providing a regulated voltage on a regulated- voltage node, the method comprising: providing a first data-dependent current from a supply node to the regulated- voltage node to develop the regulated voltage on the regulated- voltage node; providing a second data-dependent current from the supply node to a replica- voltage node to develop a replica voltage on the replica- voltage node; comparing the replica voltage to a reference voltage; and changing the first data-dependent current based on the comparing.

7. The method of claim 6, further comprising comparing the regulated voltage to the reference voltage and changing the first data-dependent current based on differences between the regulated and reference voltages.

8. The method of claim 6, wherein drawing the first data-dependent current comprises transmitting or receiving data.

9. The method of claim 7, wherein the first data-dependent current is substantially greater than the second data-dependent current.

10. A computer-readable medium having stored thereon a data structure defining a data- dependent voltage regulator, the data structure comprising: first data representing a power-supply node to receive a supply voltage and a supply current, a regulated-supply node to a provide a regulated supply voltage, and a data port to receive data; second data representing a regulated- voltage current path between the power- supply node and the regulated-supply node to convey the regulated supply voltage; third data representing a replica- voltage current path extending from the power- supply node to convey a replica voltage; fourth data representing a replica load having a replica data port connected to the data port to receive the data, a replica supply node connected to the replica- voltage current path to receive the replica voltage, the replica load to draw a data-dependent replica current from the supply node and to modulate the replica current using the data; and fifth data representing a feedback path between the replica supply node and the regulated- voltage current path, the feedback path to control the regulated-supply current responsive to data-dependent changes to the replica voltage.

11. A voltage regulator comprising: a power-supply node to receive a supply voltage and a supply current; a regulated-supply node to a provide a regulated supply voltage; a data port to receive data; means for drawing a first data-dependent current from the supply node to the regulated- voltage node to develop the regulated voltage on the regulated- voltage node; means for drawing a second data-dependent current from the supply node to a replica- voltage node to develop a replica voltage on the replica- voltage node; means for comparing the replica voltage to a reference voltage; and means for changing the first data-dependent current based on the comparing.

12. The voltage regulator of claim 11 , wherein the sum of the first and second data- dependent currents equals the supply current, and wherein the first data-dependent current is greater than the second data-dependent current.

13. An integrated circuit comprising: communication circuitry having an input port to receive data, a regulated-supply node to receive a regulated supply voltage , and a data output port, the communication circuitry to draw a data-dependent supply current from the regulated-supply node using the received data to communicate the data on the data output port as data symbols; and a data-dependent voltage regulator having a regulator data port to receive the data, a power-supply node to receive a power-supply voltage, and a regulator output node connected to the regulated-supply node to provide the regulated supply voltage and data-dependent supply current to the communication circuit, the data-dependent voltage regulator including: a regulated- voltage current path between the power-supply node and the regulator output node to convey the regulated supply voltage and the regulated- supply current; a replica- voltage current path extending from the power-supply node to convey a replica voltage; a replica load having a replica data port connected to the regulator data port to receive the data, a replica supply node connected to the replica- voltage current path to receive the replica voltage, the replica load to draw a data- dependent replica current from the replica supply node and to modulate the replica current using the data; and a feedback path between the replica supply node and the regulated- voltage current path, the feedback path to control the regulated-supply current responsive to data-dependent changes to the replica voltage.

14. The integrated circuit of claim 13, wherein the sum of the regulated-supply current and replica current is data-dependent.

15. The integrated circuit of claim 13, further comprising a second feedback path between the regulator output node and the regulated- voltage current path.

16. The integrated circuit of claim 13, wherein the feedback path also extends to the replica- voltage current path.

17. The integrated circuit of claim 13, wherein the communication circuit comprises a transmitter.

18. The integrated circuit of claim 17, wherein the communication circuit comprises a receiver, and wherein both the transmitter and the receiver are connected to the data- dependent voltage regulator.

19. The integrated circuit of claim 13, wherein the communication circuit comprises a sampler to sample the data, and wherein the data received by the replica load is the sampled data.

20. The integrated circuit of claim 13, wherein the replica load further comprises a clock port to receive a clock signal.