CN1521584A - Automatic adjustment system for mismatching of source current and sink current - Google Patents

Abstract

The invention provides an automatic adjustment system for mismatching of source current and sink current, which uses a starting compensation/setting device to perform starting current compensation and establish a control reference table according to the starting current compensation; a judging device for sending out a control signal according to the control reference table; and a current compensation device for adjusting the on and off of the internal switch according to the control signal to achieve the purpose of automatically adjusting the mismatching of the source current and the sink current.

Description

Automatic Adjustment System for Source and Sink Current Mismatches

technical field

The present invention relates to an automatic adjustment system for source current and sink current mismatch, which establishes a control reference table to provide a judging device and a current compensation device for mismatching source current (source current) and Sink current, used to perform current compensation.

Background technique

In a typical communication transceiver integrated circuit (transceiver IC), a standard phase locked loop synthesizer (phase locked loop (PLL) synthesizer) is a commonly used component, which is basically shown in Figure 1, including a reference Oscillator (reference oscillator) 10 and a reference frequency divider (reference divider) 11, to provide a reference frequency (reference frequency) Fref; A voltage-controlled oscillator (voltage-controlled oscillator) 14 and a main frequency divider (main divider) ) 13 to provide a main frequency (main frequency) Fmain; a phase detector (phase detector) 12 and a loop filter (loopfilter) 15 to compare the reference and main two frequencies to generate a feedback frequency (feedback frequency) Fback output to the voltage-controlled oscillator 14 to generate an operating frequency (operating frequency) Fout output.

However, as mentioned above, PLL synthesizers often have many significant problems, such as phase noises, non-linear effects, reference spurs, and so on. Among them, one of the sources of the above problems is the mismatch between the source current and the sink current entering and leaving the loop filter 15 . Accordingly, it is necessary to design a charge pump circuit to automatically adjust the mismatched source current and sink current to solve the above problems.

Contents of the invention

Therefore, an object of the present invention is to provide an automatic adjustment system for source current and sink current mismatch, which can automatically adjust the mismatched source current and sink current to achieve current balance and reduce phase noises.

The present invention provides an automatic adjustment system for source current and sink current mismatch, which can automatically adjust the mismatched source current and sink current to reduce spurs. The system mainly includes: a starting compensation/setting device for starting current compensation and establishing a control reference table accordingly; a judging device connected to the starting compensation/setting device through a first switch for controlling A reference table, sending a control signal; and a current compensation device, connected to the judgment device and connected to the startup compensation/setting device through a second switch, so as to adjust the opening and closing of its internal switch according to the above-mentioned control signal, In order to achieve the purpose of automatically adjusting the mismatch between source current and sink current.

The present invention also provides an automatic adjustment system for source current and sink current mismatch, including: a first compensation unit, including a plurality of circuits composed of a first constant current source and a first switch connected in series, all of the first compensation unit The input end of a constant current source is connected to a positive voltage source and the opening ends of all first switches are connected to a transmission line to compensate the source current; a second compensation unit includes a plurality of second constant current sources and second A circuit composed of switches connected in series, the output ends of all the second constant current sources are connected to a ground voltage and the open ends of all the first switches are connected to a transmission line and form a fence with the first compensation unit to compensate sink current ; A first switch has a joint end and an open end, and its joint end is connected to the transmission line, which is used to close to form a path when the system is started, and to open to form an open circuit after the start is completed; a detection resistor, connected to To the open end of the first switch, used to detect whether the source current and the sink current do not match; an amplifier has a positive input terminal, a negative input terminal, a first output terminal and a second output terminal, Its positive input end is connected to the open end of the first switch and its negative input end is connected to the free end of the detection resistor, which is used to compare the current difference between the two ends of the detection resistor, and the maximum difference and the minimum difference are passed through the first switch respectively. An output terminal and the second output terminal output; an analog-to-digital converter connected to the first and second output terminals of the amplifier for converting the above-mentioned maximum difference value and minimum difference value from analog to digital form; a logic a controller, connected to the above-mentioned analog-to-digital converter, used to establish a control reference table according to the above-mentioned digitized maximum and minimum differences, so as to provide the required current compensation reference; a second switch with an open end and a junction terminal, the joint end of which is connected to the logic controller; a selector, connected to the open end of the second switch, for outputting a control signal according to the control reference table and a comparison value after the second switch is turned off Current compensation is performed by turning on one or more of the plurality of series circuits in the first compensation unit or the second compensation unit, so that the sink current and the source current are matched.

Therefore, the present invention can automatically adjust the unmatched source current and sink current, and further solve the problems of phase noise, nonlinear effect and reference stray.

Description of drawings

In order to make the above-mentioned and other objects, features, and advantages of the present invention more obvious, a preferred embodiment is specifically cited below, together with the accompanying drawings, and described in detail as follows:

Figure 1 shows a block diagram of a typical phase-locked loop synthesizer (PLL synthesizer);

figure 2;

Fig. 3 shows a schematic diagram of the internal circuit of the current compensation device in Fig. 2 according to the present invention;

Figure 4 shows a schematic diagram of the internal circuit of the startup compensation/setting device in Figure 2 according to the present invention; and

FIG. 5 shows a schematic diagram of the internal circuit of the judging device in FIG. 2 according to the present invention.

Symbol Description

10: Reference oscillator (reference oscillator)

11: Reference divider (reference divider)

12: phase detector (phase detector)

13: main divider (main divider)

14, 25: voltage-controlled oscillator (voltage-controlled oscillator)

15: loop filter (loop filter)

21: current compensation device (current compensation device)

22: Start compensation/settings device (initialization compensation/settings device)

23: Judgment device (adjustment device)

24: Low pass filter (lowpass filter)

51: Comparator

53: selector

55: bandgap reference circuit

VCC: voltage source (voltage source)

GND: ground (ground)

Isr, Isk, I11-I1N, I21-I2N: constant current source

S1, S2, SW11-SW1N, SW21-SW2N: switch

Detailed ways

Figure 2 shows a block diagram of the inventive system. In FIG. 2 , the device mainly includes: a startup compensation/setting device 22 ; a judging device 23 ; and a current compensation device 21 . Among them, the devices 21 and 22 are connected by the switch S1, and the devices 22 and 23 are connected by the switch S2.

As shown in Figure 2, when an external voltage VCC is provided to the system, due to the difference in the characteristics of the P-type and N-type semiconductor devices, a constant current of a source current Isr will be generated between the voltage VCC and the intermediate terminal M. In addition, , between the intermediate terminal M and the ground terminal GND, another constant current sink current Isk will be generated. Basically, the source current Isr should be equal to the sink current Isk, so that a stable current and voltage can be provided for the connected low-pass filter 24 and the VCO 25 to operate. However, limited by communication specifications such as heat and phase margin, the source current Isr is often not equal to the sink current Isk. Therefore, at start-up, the switch S1 is closed to conduct the device 22 for start-up compensation. To start the compensation, the device 22 can directly control the device 21 (dotted line) to perform compensation, or close the switch S2, and the device 22 indirectly sends a control signal Sc through the device 23 to control the device 21 (solid line) to perform current compensation. At the same time, after starting the compensation, the device 22 will establish a reference index (reference index) to establish a logic control table (logic control table). After the table is established, the switch S1 will be opened (open) to cut off the connection with the device 21, so as to prevent initialization compensation (initialization compensation) from happening again and affecting the overall operation.

As shown in FIG. 2 , once a mismatch occurs between the source current Isr and the sink current Isk, the device 23 can send a logic control signal to the device 21 according to the above logic control table. In this way, the device 21 will adjust the current according to the above logic control signal, so as to achieve the purpose of automatically adjusting the mismatch between the source current and the sink current. The internal circuits of each device are further described below.

FIG. 3 shows a schematic diagram of the internal circuit of the current compensation device 21 in FIG. 2 according to the present invention. In FIG. 3 , the device 21 mainly includes a plurality of first switches (first switches) SW11-SW1N, a first constant current source I11-I1N connected in series to the first switches 1 to 1, and a plurality of second switches ( second switches) SW21-SW2N and the second constant current sources I21-I2N connected in series to the second switch in a 1-to-1 manner; wherein, the input terminals of all the first constant current sources are connected to the external voltage VCC, and all the second constant current sources The output terminal of the source is grounded, and the open terminals of all the switches SW11-SW2N are connected to a transmission line L to form a railing implementation. One end of the transmission line L is connected to the voltage-controlled oscillator 25 ( FIG. 2 ) through the low-pass filter 24 , and the other end is connected to the terminal M in FIG. 2 .

As shown in FIG. 3, during operation, when the voltage Vtune input to the component 25 is higher than a first predetermined value (the source current Isr is lower than the sink current Isk), a control signal Sc (described later) is input to close (close) The required first switch creates a current path, causing a corresponding constant current source to flow on the transmission line L. The above activation method starts from SW11 and closes the switches on the same side in order to form a pathway, so that the corresponding constant current source supply (sourcing) current flows to the transmission line L, so as to increase Source current (or reduce sink current) is supplied until the voltage input to the component 25 is lower than a first predetermined value (source current Isr is approximately equal to sink current Isk). Similarly, when the voltage Vtune input to the component 25 is lower than a second predetermined value (the source current Isr is higher than the sink current Isk), a control signal Sc (described later) is input to turn off the required second switch to generate a current path, Cause the corresponding constant flow source to flow to the ground. The above driving method starts from SW21 and turns off the switches on the same side in order to form a path, so that the corresponding constant current source sinks the current through the ground, so as to reduce the source current (or increase the sink current) until the input Until the voltage of the component 25 is higher than the second predetermined value (the source current Isr is approximately equal to the sink current Isk).

FIG. 4 shows a schematic diagram of the internal circuit 22 of the startup compensation/setting device in FIG. 2 according to the present invention. In Fig. 4, in order to provide the required predetermined value and do current-calibrated compensation (current-calibrated compensation) when just starting, to provide the setting standard of each predetermined value, so this circuit 22 includes a detection resistor Rt, an amplifier A. An analog-to-digital converter 42 and a logic controller 43 .

As shown in Figure 4, due to the mismatch between the source current and the sink current, it will be reflected in the voltage values at the front and rear ends of the detection resistor Rt (that is, the current flowing into and out of the resistor is not equal), so when the current source Isr, When Isk is initially turned on and the switch S1 is turned off, the voltages Vcp and Vref flowing through the detection resistor Rt are compensated (judged) by the amplifier 41 and the converter 42 and digitally converted to generate a digital reference signal V _tH and V _tL are input to the logic controller 43 for storage. The execution of the compensation action can directly input the signals V _tH and V _tL to the device 21 for compensation, or, the logic controller 43 converts the signals V _tH and V _tL into an output signal Sout, and then inputs it to the subsequent judgment The device 23 refers to generate a control signal Sc (described later). In addition, the logic controller 43 can set equidistant or unequal step correction ranges according to the reference signals V _tH and V _tL for current compensation after startup.

FIG. 5 shows a schematic diagram of the internal circuit of the judging device in FIG. 2 according to the present invention. In FIG. 5, the circuit mainly includes a bandgap reference circuit (bandgap reference circuit) 55 to output a reference voltage Vt and a comparator 51 to compare the reference voltage and the voltage Vtune input to the oscillator to generate a comparison signal Scomp and a selector 53 refer to the signal Sout from the device 22 according to the comparison signal to generate the control signal Sc.

As shown in FIG. 5, the output result Scomp generated by the comparison of the comparator 51 is only a differential value, which is not enough to know whether the source current or the sink current should be compensated, let alone how much current should be compensated. To achieve the purpose of matching the sink current and the source current, the built-in table in the device 22 must be used to provide the reference value required for current compensation. For example, in the device 21, if N=8, the signal Sout can have a logic value of 0001 to indicate that the switch SW11 is turned off for source current compensation; 0010 means that the switches SW11 and SW12 are turned off for source current compensation; 0011 means that the switches SW11 and SW12 are turned off and SW13 are turned off for source current compensation... etc.; and 1001 means that switch SW21 is turned off for sink current compensation; 1010 means that switches SW21 and SW22 are turned off for sink current compensation; 1011 means that switches SW21, SW22 and SW23 are turned off for Do current compensation...etc. In addition, the above-mentioned logic value can also be converted into a stepped reference signal through a digital/analog converter (it can also be placed in the logic controller of the device 22 to directly become the output signal Sout), for example, the logic value 0001 represents 0.0 -1.0 volt output, 0010 for 1.1-2.0 volt output, 0011 for 2.1-3.0 volt output, etc.; logic value 1001 for 0.0 to -1.0 volt output; 1010 for -1.1 to -2.0 volt output; 1011 for -2.1 to - 3.0 volt output and so on. As mentioned above, the purpose of matching sink current and source current can be achieved.

Although the present invention has been disclosed above with a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection shall prevail as defined by the appended claims.

Claims (8)

1. An automatic adjustment system for source current and sink current mismatch, comprising: A starting compensation/setting device for starting current compensation and establishing a control reference table accordingly; A judging device, connected to the starting compensation/setting device through a first switch, so as to send a control signal according to the above-mentioned control reference table; and A current compensation device, connected to the judgment device and connected to the startup compensation/setting device through a second switch, to adjust the opening and closing of the first switch and the second switch according to the above-mentioned control signal, thereby automatically Adjust the source and sink currents until they match. 2. The automatic adjustment system for source current and sink current mismatch according to claim 1, wherein the second switch is opened to form an open circuit state after starting current compensation, and the first switch is kept closed to form a circuit state . 3. The automatic adjustment system for source current and sink current mismatch as claimed in claim 1, further comprising: a transmission line connecting the current compensation device to the startup compensation/setting device; A combination of at least one first constant current source and at least one third switch connected in series, and one end of the series combination is connected to the transmission line, and the other end is connected to a positive voltage source; A combination of at least one second constant current source and at least one fourth switch connected in series, and one end of the series combination is connected to the transmission line, and the other end is connected to a ground voltage. 4. The automatic adjustment system for source current and sink current mismatch as claimed in claim 1, wherein the start-up compensation/setting device is composed of a sense resistor, an amplifier whose negative input terminal is connected to the sense resistor, a string It is composed of an analog-to-digital converter connected to the amplifier and a logic controller connected in series to the analog-to-digital converter. 5. The automatic adjustment system for source current and sink current mismatch as claimed in claim 1, wherein the judging device is composed of a bandgap reference circuit, a comparator whose negative input terminal is connected to the bandgap reference circuit It is composed of a selector whose two input ends are respectively connected to the comparator and the switch, and whose output end is connected to the current compensation device. 6. An automatic adjustment system for source current and sink current mismatch, comprising: A first compensation unit, including a plurality of circuits composed of first constant current sources and first switches connected in series, the input ends of all first constant current sources are connected to a positive voltage source and the open ends of all first switches are connected to to a transmission line for compensating the source current; A second compensation unit, including a plurality of circuits composed of second constant current sources and second switches connected in series, the output ends of all second constant current sources are connected to a ground voltage and the open ends of all first switches are connected to a transmission line forming a fence shape with the first compensation unit for compensating sink current; a first switch having a joint end and an open end, the joint end is connected to the transmission line, and is used to close to form a path when the system starts up, and to open to form a break circuit after the start-up is completed; a detection resistor, connected to the open end of the first switch, for detecting whether the source current and the sink current do not match; An amplifier has a positive input terminal, a negative input terminal, a first output terminal and a second output terminal, its positive input terminal is connected to the open end of the first switch and its negative input terminal is connected to the detection resistor a free terminal, used to compare the current difference between the two ends of the detection resistor, and output the maximum difference and the minimum difference respectively through the first output terminal and the second output terminal; An analog-to-digital converter, connected to the first and second output terminals of the amplifier, is used to convert the above-mentioned maximum difference value and minimum difference value from analog to digital form; A logic controller, connected to the above-mentioned analog-to-digital converter, is used to establish a control reference table according to the above-mentioned digitized maximum and minimum differences, so as to provide the required current compensation reference; a second switch having an open end and an engaging end connected to the logic controller; A selector, connected to the open end of the second switch, for outputting a control signal to turn on the first compensation unit or the second compensation unit according to the control reference table and a comparison value after the second switch is turned off. One or more of the plurality of series circuits in the compensation unit is used for current compensation, so that the sink current and the source current are matched. 7. The automatic adjustment system for source current and sink current mismatch as claimed in claim 6, further comprising a low-pass filter connected to the transmission line and the junction of the first switch for filtering to remove unwanted signals and generate an output voltage. 8. The automatic adjustment system for source current and sink current mismatch as claimed in claim 7, wherein the selector further comprises a comparator connected to the low pass filter to receive an output from the low pass filter voltage, and compared with a reference voltage from an external bandgap reference circuit to generate an output of the comparison value.

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