A process variation auto-tuning circuit for voltage reference source

Abstract

The application belongs to the technical field of integrated circuits, and particularly relates to a process deviation automatic trimming circuit for a voltage reference source, which specifically comprises a voltage reference, a current source generation circuit, a process deviation detection circuit, a decoder and a trimming circuit, and is characterized in that the process deviation detection circuit is composed of several types of different resistors under the same process library, can accurately detect the process deviation amount, can accurately trim the reference voltage source, and realizes high-precision output of the reference voltage source. The process deviation automatic trimming circuit for the voltage reference source has simple structure, small layout area, and no external trimming pin of the chip, can automatically detect the process deviation amount, and automatically trims the reference voltage source according to the process deviation. The process deviation automatic trimming circuit for the voltage reference source can greatly reduce the chip production cost and the chip testing cost in the later stage.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of integrated circuits, and particularly relates to a process deviation automatic trimming circuit for a voltage reference source. BACKGROUND

[0002] High-precision voltage reference sources are usually required in analog integrated circuits to provide reference voltages for circuits, such as high-precision low-dropout linear voltage regulators, high-precision analog-to-digital converters, high-precision digital-to-analog converters, etc. Voltage reference sources need to have high stability, high precision, and characteristics of not changing with temperature, process, and power supply voltage. However, the deviation of integrated circuit production processes inevitably affects the output precision of voltage reference sources. To improve the precision of reference voltage sources, the traditional approach is to add a dedicated trimming pin outside the chip for trimming the voltage source, which means an increase in chip layout area and manufacturing cost, and the trimming pin also increases the complexity of subsequent chip debugging. SUMMARY

[0003] The present application is to solve the above problems, and provides a process deviation automatic trimming circuit for a voltage reference source.

[0004] To achieve the above object, the present application adopts the following technical scheme:

[0005] A process deviation automatic trimming circuit for a voltage reference source, comprising a voltage reference, a current source generation circuit, a process deviation detection circuit, a decoder, and a trimming circuit, characterized in that the circuit does not require a trimming pin outside the chip, can automatically detect the process deviation amount, and automatically trims the reference voltage source according to the process deviation.

[0006] The current source generation circuit is used to generate a temperature-independent and stable current. Specifically, the current source generation circuit comprises an error amplifier, a first MOS transistor M1, a fifth MOS transistor M5, and a low-process-sensitivity zero-temperature resistance string L3. The non-inverting input terminal of the error amplifier is connected to the voltage reference output V REF , the inverting input terminal of the error amplifier is connected to the source terminal of the fifth MOS transistor M5, and the output terminal of the error amplifier is connected to the gate terminal of the fifth MOS transistor M5; the gate terminal of the first MOS transistor M1 is connected to the drain terminal of the first MOS transistor M1, the source terminal of the first MOS transistor M1 is connected to the power supply voltage VIN, the drain terminal of the first MOS transistor M1 is connected to the drain terminal of the fifth MOS transistor M5, and the gate terminal of the first MOS transistor M1 is the output V IBIS of the current source generation circuit; the source terminal of the fifth MOS transistor M5 is connected to the upper end of the low-process-sensitivity zero-temperature resistance string L3; and the lower end of the low-process-sensitivity zero-temperature resistance string L3 is connected to the GND potential.

[0007] The process deviation detection circuit is used for detecting process deviation in chip production. Specifically, the process deviation detection circuit comprises a second MOS transistor M2, a third MOS transistor M3, a fourth MOS transistor M4, a low-process-sensitivity zero-temperature resistance string L1, a low-process-sensitivity zero-temperature resistance string L2, a high-process-sensitivity zero-temperature resistance string H1, a comparator 1, and a comparator 2. The gate of the second MOS transistor M2 is connected to the output end V of the current source generation circuit, the source of the second MOS transistor M2 is connected to a power supply voltage V, and the drain of the second MOS transistor M2 is connected to the upper end V of the low-process-sensitivity zero-temperature resistance string L1 and the positive input end of the comparator 1. The lower end of the low-process-sensitivity zero-temperature resistance string L1 is connected to a GND potential. The gate of the third MOS transistor M3 is connected to the output end V of the current source generation circuit, the source of the third MOS transistor M3 is connected to the power supply voltage V, and the drain of the third MOS transistor M3 is connected to the upper end V of the low-process-sensitivity zero-temperature resistance string L2 and the positive input end of the comparator 2. The lower end of the low-process-sensitivity zero-temperature resistance string L2 is connected to the GND potential. The gate of the fourth MOS transistor M4 is connected to the output end V of the current source generation circuit, the source of the fourth MOS transistor M4 is connected to the power supply voltage V, and the drain of the fourth MOS transistor M4 is connected to the upper end V of the high-process-sensitivity zero-temperature resistance string H1. The lower end of the high-process-sensitivity zero-temperature resistance string H1 is connected to the GND potential. The positive input end of the comparator 1 is connected to the upper end V of the low-process-sensitivity zero-temperature resistance string L1, and the negative input end of the comparator 1 is connected to the upper end V of the high-process-sensitivity zero-temperature resistance string H1. The positive input end of the comparator 2 is connected to the upper end V of the low-process-sensitivity zero-temperature resistance string L2, and the negative input end of the comparator 2 is connected to the upper end V of the high-process-sensitivity zero-temperature resistance string H1. IBIAS IN C IBIAS IN B IBIAS IN A C A B A

[0008] The decoder is used for generating logic trimming codes required under different process deviations. The input end D1 of the decoder is connected to the output end of the comparator 1, and the input end D2 of the decoder is connected to the output end of the comparator 2.

[0009] The trimming circuit is used for trimming the reference voltage value according to the process deviation. The input end of the trimming circuit is connected to the output end of the decoder, and the output end of the trimming circuit is connected to a reference voltage trimming network.

[0010] ​​​​​​​​​​​​​The low-process-sensitivity zero-temperature resistor string L1 is used to generate a voltage that varies little with process deviations. The low-process-sensitivity zero-temperature resistor string L1 has a zero temperature coefficient, and the voltage V at the upper end of the low-process-sensitivity zero-temperature resistor string L1 is... C With minimal variation due to process deviation, the voltage V at the upper end of the low process sensitivity zero-temperature resistor series L1 is... C The voltage V at the upper end of the low process sensitivity zero-temperature resistor series L2 is greater than that of the aforementioned voltage. B Specifically, the low-process-sensitivity zero-temperature resistor string L1 includes a first resistor R1 and a second resistor R2. The resistance value of the first resistor R1 changes little with process offset, and the resistance value of the first resistor R1 increases with temperature. The upper end of the first resistor R1 is connected to the drain terminal of the second MOSFET M2 and the upper end of the second resistor R2, and the lower end of the first resistor R1 is connected to the lower end of the second resistor R2 and the GND potential. The resistance value of the second resistor R2 changes little with process offset, and the resistance value of the second resistor R2 decreases with temperature. The upper end of the second resistor R2 is connected to the drain terminal of the second MOSFET M2 and the upper end of the first resistor R1, and the lower end of the second resistor R2 is connected to the lower end of the first resistor R1 and the GND potential.

[0011] The low-process-sensitivity zero-temperature resistor string L2 is used to generate a voltage that varies little with process deviations. The low-process-sensitivity zero-temperature resistor string L2 has a zero temperature coefficient, and the voltage V at the upper end of the low-process-sensitivity zero-temperature resistor string L2 is... B The voltage V at the upper end of the low process sensitivity zero-temperature resistor series L2 varies little with process deviation. B The voltage V at the upper end of the low process sensitivity zero-temperature resistor series L1 is less than that of the low process sensitivity zero-temperature resistor series L1. C Specifically, the low-process-sensitivity zero-temperature resistor string L2 includes a third resistor R3 and a fourth resistor R4. The resistance value of the third resistor R3 changes little with process offset, and increases with temperature. The upper end of the third resistor R3 is connected to the drain of the third MOS transistor M3 and the upper end of the fourth resistor R4, and the lower end of the third resistor R3 is connected to the lower end of the fourth resistor R4 and the GND potential. The resistance value of the fourth resistor R4 changes little with process offset, and decreases with temperature. The lower end of the fourth resistor R4 is connected to the drain of the third MOS transistor M3 and the upper end of the third resistor R3, and the lower end of the fourth resistor R4 is connected to the lower end of the third resistor R3 and the GND potential.

[0012] The low-process-sensitivity zero-temperature-resistance string L3 is used to generate a current which does not change with temperature, and has a zero temperature coefficient. Specifically, the low-process-sensitivity zero-temperature-resistance string L3 comprises a seventh resistor R7 and an eighth resistor R8. The resistance value of the seventh resistor R7 changes less with process offset, and the resistance value of the seventh resistor R7 increases with temperature rise. The upper end of the seventh resistor R7 is connected to the source end of the fifth MOS tube M5 and the inverting input end of the error amplifier. The lower end of the seventh resistor R7 is connected to the lower end of the eighth resistor R8 and the GND potential. The resistance value of the eighth resistor R8 changes less with process offset, and the resistance value of the eighth resistor R8 decreases with temperature rise. The upper end of the eighth resistor R8 is connected to the source end of the fifth MOS tube M5 and the inverting input end of the error amplifier. The lower end of the eighth resistor R8 is connected to the lower end of the seventh resistor R7 and the GND potential.

[0013] The high-process-sensitivity zero-temperature-resistance string H1 is used to generate a voltage which changes greatly with process offset, and has a zero temperature coefficient. The high-process-sensitivity zero-temperature-resistance string H1 has a high-process-sensitivity zero-temperature-resistance string H1 upper end voltage V A changes greatly with process offset. Specifically, the high-process-sensitivity zero-temperature-resistance string H1 comprises a fifth resistor R5 and a sixth resistor R6. The resistance value of the fifth resistor R5 changes greatly with process offset, and the resistance value of the fifth resistor R5 increases with temperature rise. The upper end of the fifth resistor R5 is connected to the drain end of the fourth MOS tube M4. The lower end of the fifth resistor R5 is connected to the upper end of the sixth resistor R6. The resistance value of the sixth resistor R6 changes greatly with process offset, and the resistance value of the sixth resistor R6 increases with temperature rise. The upper end of the sixth resistor R6 is connected to the lower end of the fifth resistor R5. The lower end of the sixth resistor R6 is connected to the GND potential.

[0014] Compared with the prior art, the present application has the beneficial effects that: the present application proposes a process offset automatic trimming circuit for a voltage reference source. Different resistors in the same process library have different sensitivity to process offset. The process offset is detected and quantified, so that the function of trimming the output voltage of the voltage reference source according to different process offsets is realized. The process offset detection circuit in the present application is composed of several types of resistors, which can accurately detect the process offset, so that the reference voltage source can be accurately trimmed, and high-precision output of the reference voltage source is realized. The circuit structure is simple, the layout area is small, and the chip production cost and the later chip test cost can be greatly reduced. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 A process offset automatic trimming circuit for a voltage reference source is proposed in the present application.

[0016] Figure 2 Circuit diagram of current source generating circuit;

[0017] Figure 3 Circuit diagram of process deviation detection circuit;

[0018] Figure 4 Waveform diagram of key nodes of process deviation automatic trimming circuit for voltage reference source proposed by the present application shifting with process.

[0019] Figure 5 Circuit diagram of low process sensitivity zero temperature resistance string L1;

[0020] Figure 6 Circuit diagram of low process sensitivity zero temperature resistance string L2;

[0021] Figure 7 Circuit diagram of high process sensitivity zero temperature resistance string H1;

[0022] Figure 8 Circuit diagram of low process sensitivity zero temperature resistance string L3;

[0023] Figure 9 Curve diagram of resistance values of different resistances changing with process shift;

[0024] Figure 10 Curve diagram of equivalent resistance values of high process sensitivity zero temperature resistance string H1, low process sensitivity zero temperature resistance string L1, low process sensitivity zero temperature resistance string L2, low process sensitivity zero temperature resistance string L3 changing with temperature. DETAILED DESCRIPTION

[0025] As shown in Figure 1 , a process deviation automatic trimming circuit for voltage reference source includes voltage reference, current source generating circuit, process deviation detection circuit, decoder, trimming circuit, characterized in that: the process deviation detection circuit is composed of several types of different resistances under the same process library, which can accurately detect the process deviation amount, so as to accurately trim the reference voltage source and realize high-precision output of the reference voltage source. The circuit does not need external trimming pins of the chip, can automatically detect the process deviation amount, and automatically trim the reference voltage source according to the process deviation.

[0026] As shown in Figure 2 , the current source generating circuit is used to generate a temperature-independent and stable current. Specifically, the current source generating circuit includes error amplifier, first MOS tube M1, fifth MOS tube M5, low process sensitivity zero temperature resistance string L3. The positive input end of the error amplifier is connected with the voltage reference output V REF, the error amplifier inverting input end connects the fifth MOS tube M5 source end, the error amplifier output end connects the fifth MOS tube M5 grid end; the first MOS tube M1 grid end connects the first MOS tube M1 drain end, the first MOS tube M1 source end connects power supply voltage V IN , the first MOS tube M1 drain end connects the fifth MOS tube M5 drain end, the first MOS tube M1 grid end is the output V IBIS of the current source generation circuit;The fifth MOS tube M5 source end connects the low process sensitivity zero temperature resistance string L3 upper end;The low process sensitivity zero temperature resistance string L3 lower end connects GND potential.

[0027] As Figure 3 shown, the process deviation detection circuit is used for detecting process deviation in chip production. Specifically, the process deviation detection circuit includes a second MOS tube M2, a third MOS tube M3, a fourth MOS tube M4, a low process sensitivity zero temperature resistance string L1, a low process sensitivity zero temperature resistance string L2, a high process sensitivity zero temperature resistance string H1, a comparator 1, and a comparator 2. The second MOS tube M2 grid end connects the output end V IBIAS of the current source generation circuit, the second MOS tube M2 source end connects the power supply voltage V IN , the second MOS tube M2 drain end connects the low process sensitivity zero temperature resistance string L1 upper end V C and the comparator 1 positive input end;The low process sensitivity zero temperature resistance string L1 lower end connects GND potential;The third MOS tube M3 grid end connects the output end V IBIAS of the current source generation circuit, the third MOS tube M3 source end connects the power supply voltage V IN , the third MOS tube M3 drain end connects the low process sensitivity zero temperature resistance string L2 upper end V B and the comparator 2 positive input end;The low process sensitivity zero temperature resistance string L2 lower end connects GND potential;The fourth MOS tube M4 grid end connects the output end V IBIAS of the current source generation circuit, the fourth MOS tube M4 source end connects the power supply voltage V IN , the fourth MOS tube M4 drain end connects the high process sensitivity zero temperature resistance string H1 upper end V A ;The high process sensitivity zero temperature resistance string H1 lower end connects GND potential;The comparator 1 positive input end connects the low process sensitivity zero temperature resistance string L1 upper end V C , the comparator 1 inverting input end connects the high process sensitivity zero temperature resistance string H1 upper end V A ;The comparator 2 positive input end connects the low process sensitivity zero temperature resistance string L2 upper end V BThe comparator 2 reverses input end is connected to the high process sensitivity zero temperature resistance string H1 upper end V A .

[0028] As shown in Figure 4 , Figure 10 , under different process deviation, the low process sensitivity zero temperature resistance string L1 equivalent resistance value is greater than the low process sensitivity zero temperature resistance string L2 resistance value; the low process sensitivity zero temperature resistance string L1 and the low process sensitivity zero temperature resistance string L2 equivalent resistance value changes less with process deviation resistance value, the high process sensitivity zero temperature resistance string H1 changes more with process deviation resistance value; under SS process angle, the high process sensitivity zero temperature resistance string H1 upper end voltage V A is higher than the low process sensitivity zero temperature resistance string L1 upper end voltage V C and the low process sensitivity zero temperature resistance string L2 upper end voltage V B , so the comparator 1 output end D1 is low level, the comparator 2 output end D2 is low level. Under TT process angle, the high process sensitivity zero temperature resistance string H1 upper end voltage V A is lower than the low process sensitivity zero temperature resistance string L1 upper end voltage V C , the high process sensitivity zero temperature resistance string H1 upper end voltage VA is higher than the low process sensitivity zero temperature resistance string L2 upper end voltage V B , so the comparator 1 output end D1 is high level, the comparator 2 output end D2 is low level. Under FF process angle, the high process sensitivity zero temperature resistance string H1 upper end voltage V A is lower than the low process sensitivity zero temperature resistance string L1 upper end voltage V C and the low process sensitivity zero temperature resistance string L2 upper end voltage V B , so the comparator 1 output end D1 is high level, the comparator 2 output end D2 is high level. Therefore, under different process deviation, the comparator 1 and the comparator 2 output different high and low level, after decoder processing, control the trimming circuit to carry out high precision trimming to the reference voltage source.

[0029] The decoder is used to generate the logic trimming code required under different process deviation, the decoder input end D1 is connected to the comparator 1 output end, the decoder input end D2 is connected to the comparator 2 output end.

[0030] The trimming circuit is used for trimming the reference voltage value according to process deviation, the trimming circuit input end is connected to the decoder output end, and the trimming circuit output end is connected to the reference voltage trimming network.

[0031] As shown in Figure 5 , Figure 9As shown, the low-process-sensitivity zero-temperature resistor string L1 is used to generate a voltage that varies little with process deviations. The low-process-sensitivity zero-temperature resistor string L1 has a zero temperature coefficient, and the voltage V at the upper end of the low-process-sensitivity zero-temperature resistor string L1 is... C With minimal variation due to process deviation, the voltage V at the upper end of the low process sensitivity zero-temperature resistor series L1 is... C The voltage V at the upper end of the low process sensitivity zero-temperature resistor series L2 is greater than that of the aforementioned voltage. B Specifically, the low-process-sensitivity zero-temperature resistor string L1 includes a first resistor R1 and a second resistor R2. The resistance value of the first resistor R1 changes little with process offset, and the resistance value of the first resistor R1 increases with temperature. The upper end of the first resistor R1 is connected to the drain terminal of the second MOSFET M2 and the upper end of the second resistor R2, and the lower end of the first resistor R1 is connected to the lower end of the second resistor R2 and the GND potential. The resistance value of the second resistor R2 changes little with process offset, and the resistance value of the second resistor R2 decreases with temperature. The upper end of the second resistor R2 is connected to the drain terminal of the second MOSFET M2 and the upper end of the first resistor R1, and the lower end of the second resistor R2 is connected to the lower end of the first resistor R1 and the GND potential.

[0032] like Figure 6 , Figure 9 As shown, the low-process-sensitivity zero-temperature resistor string L2 is used to generate a voltage that varies little with process deviations. The low-process-sensitivity zero-temperature resistor string L2 has a zero temperature coefficient, and the voltage V at the upper end of the low-process-sensitivity zero-temperature resistor string L2 is... B The voltage V at the upper end of the low process sensitivity zero-temperature resistor series L2 varies little with process deviation. B The voltage V at the upper end of the low process sensitivity zero-temperature resistor series L1 is less than that of the low process sensitivity zero-temperature resistor series L1. C Specifically, the low-process-sensitivity zero-temperature resistor string L2 includes a third resistor R3 and a fourth resistor R4. The resistance value of the third resistor R3 changes little with process offset, and increases with temperature. The upper end of the third resistor R3 is connected to the drain of the third MOS transistor M3 and the upper end of the fourth resistor R4, and the lower end of the third resistor R3 is connected to the lower end of the fourth resistor R4 and the GND potential. The resistance value of the fourth resistor R4 changes little with process offset, and decreases with temperature. The lower end of the fourth resistor R4 is connected to the drain of the third MOS transistor M3 and the upper end of the third resistor R3, and the lower end of the fourth resistor R4 is connected to the lower end of the third resistor R3 and the GND potential.

[0033] like Figure 8 , Figure 9As shown, the low-process-sensitivity zero-temperature resistor string L3 is used to generate a current that does not change with temperature, and the low-process-sensitivity zero-temperature resistor string L3 has a zero temperature coefficient. Specifically, the low-process-sensitivity zero-temperature resistor string L3 includes a seventh resistor R7 and an eighth resistor R8; the resistance value of the seventh resistor R7 changes little with process offset, and the resistance value of the seventh resistor R7 increases with temperature. The upper end of the seventh resistor R7 is connected to the source terminal of the fifth MOSFET M5 and the inverting input terminal of the error amplifier, and the lower end of the seventh resistor R7 is connected to the lower end of the eighth resistor R8 and the GND potential; the resistance value of the eighth resistor R8 changes little with process offset, and the resistance value of the eighth resistor R8 decreases with temperature. The eighth resistor R8 is connected to the source terminal of the fifth MOSFET M5 and the inverting input terminal of the error amplifier, and the lower end of the eighth resistor R8 is connected to the lower end of the seventh resistor R7 and the GND potential.

[0034] like Figure 7 , Figure 9 As shown, the high process sensitivity zero-temperature resistor string H1 is used to generate a voltage that varies significantly with process deviations. The high process sensitivity zero-temperature resistor string H1 has a zero temperature coefficient, and the voltage V at the upper end of the high process sensitivity zero-temperature resistor string H1 is... A The resistance varies significantly with process deviations. Specifically, the high process-sensitive zero-temperature resistor string H1 includes a fifth resistor R5 and a sixth resistor R6. The resistance value of the fifth resistor R5 varies significantly with process deviations, increasing with temperature. The upper end of the fifth resistor R5 is connected to the drain terminal of the fourth MOS transistor M4, and the lower end of the fifth resistor R5 is connected to the upper end of the sixth resistor R6. The resistance value of the sixth resistor R6 also varies significantly with process deviations, increasing with temperature. The upper end of the sixth resistor R6 is connected to the lower end of the fifth resistor R5, and the lower end of the sixth resistor R6 is connected to the GND potential.

[0035] In summary, this invention proposes an automatic process deviation adjustment circuit for voltage reference sources. It utilizes the different sensitivities of resistance values ​​to process deviations within the same process library to detect and quantify process deviations, thereby enabling the adjustment of the voltage reference source output voltage based on different process deviations. The proposed process deviation detection circuit consists of several different types of resistors, accurately detecting the amount of process deviation, thus precisely adjusting the reference voltage source and achieving high-precision output. Furthermore, the circuit structure is simple, occupies a small layout area, and can significantly reduce chip manufacturing costs and subsequent chip testing costs.

Claims

1. An automatic process deviation correction circuit for a voltage reference source, characterized in that, The voltage reference, the current source generation circuit, the process deviation detection circuit, the decoder, and the trimming circuit are included. The current source generating circuit comprises an error amplifier, a first MOS transistor M1, a fifth MOS transistor M5 and a third low process sensitivity zero temperature resistance string L3; a positive input end of the error amplifier is connected with a voltage reference output V REF , a negative input end of the error amplifier is connected with a source end of the fifth MOS transistor M5, and an output end of the error amplifier is connected with a gate end of the fifth MOS transistor M5; a gate end of the first MOS transistor M1 is connected with a drain end of the first MOS transistor M1, a source end of the first MOS transistor M1 is connected with a power supply voltage V IN , a drain end of the first MOS transistor M1 is connected with a drain end of the fifth MOS transistor M5, and the gate end of the first MOS transistor M1 is an output end of the current source generating circuit and outputs V IBIS ; the source end of the fifth MOS transistor M5 is connected with an upper end of the third low process sensitivity zero temperature resistance string L3; a lower end of the third low process sensitivity zero temperature resistance string L3 is connected with a GND potential; The process deviation detection circuit comprises a second MOS transistor M2, a third MOS transistor M3, a fourth MOS transistor M4, a first low-process-sensitivity zero-temperature-resistance string L1, a second low-process-sensitivity zero-temperature-resistance string L2, a high-process-sensitivity zero-temperature-resistance string H1, a first comparator, and a second comparator; the gate of the second MOS transistor M2 is connected to the output end V of the current source generation circuit IBIAS , the source of the second MOS transistor M2 is connected to a power supply voltage V IN , the drain of the second MOS transistor M2 is connected to the upper end V C of the first low-process-sensitivity zero-temperature-resistance string L1 and the positive input end of the first comparator; the lower end of the first low-process-sensitivity zero-temperature-resistance string L1 is connected to a GND potential; the gate of the third MOS transistor M3 is connected to the output end V IBIAS of the current source generation circuit, the source of the third MOS transistor M3 is connected to a power supply voltage V IN , the drain of the third MOS transistor M3 is connected to the upper end V B of the second low-process-sensitivity zero-temperature-resistance string L2 and the positive input end of the second comparator; the lower end of the second low-process-sensitivity zero-temperature-resistance string L2 is connected to a GND potential; the gate of the fourth MOS transistor M4 is connected to the output end V IBIAS of the current source generation circuit, the source of the fourth MOS transistor M4 is connected to a power supply voltage V IN , and the drain of the fourth MOS transistor M4 is connected to the upper end V A of the high-process-sensitivity zero-temperature-resistance string H1; the lower end of the high-process-sensitivity zero-temperature-resistance string H1 is connected to a GND potential; the positive input end of the first comparator is connected to the upper end V C of the first low-process-sensitivity zero-temperature-resistance string L1, and the inverting input end of the first comparator is connected to the upper end V A of the high-process-sensitivity zero-temperature-resistance string H1; the positive input end of the second comparator is connected to the upper end V B of the second low-process-sensitivity zero-temperature-resistance string L2, and the inverting input end of the second comparator is connected to the upper end V A of the high-process-sensitivity zero-temperature-resistance string H1. The decoder is used to generate the logic trimming code required under different process deviations, a first input terminal D1 of the decoder is connected to an output terminal of the first comparator, and a second input terminal D2 of the decoder is connected to an output terminal of the second comparator. The trimming circuit is used to trim the reference voltage value according to the process deviation, an input terminal of the trimming circuit is connected to an output terminal of the decoder, and an output terminal of the trimming circuit is connected to a reference voltage trimming network.

2. A process variation auto-calibration circuit for a voltage reference source as recited in claim 1, wherein: The first low-process-sensitivity zero-temperature-resistance string L1 is used to generate a voltage which changes less with process deviation and has a zero temperature coefficient; the voltage V C at the upper end of the first low-process-sensitivity zero-temperature-resistance string L1 is greater than the voltage V B at the upper end of the second low-process-sensitivity zero-temperature-resistance string L2; specifically, the first low-process-sensitivity zero-temperature-resistance string L1 comprises a first resistor R1 and a second resistor R2; the resistance value of the first resistor R1 changes less with process deviation, and the resistance value of the first resistor R1 increases with temperature rise; the upper end of the first resistor R1 is connected to the drain of the second MOS transistor M2 and the upper end of the second resistor R2, and the lower end of the first resistor R1 is connected to the lower end of the second resistor R2 and the GND potential; the resistance value of the second resistor R2 changes less with process deviation, and the resistance value of the second resistor R2 decreases with temperature rise; the upper end of the second resistor R2 is connected to the drain of the second MOS transistor M2 and the upper end of the first resistor R1, and the lower end of the second resistor R2 is connected to the lower end of the first resistor R1 and the GND potential. The second low-process-sensitivity zero-temperature-resistance string L2 is used to generate a voltage which changes less with process deviation and has a zero temperature coefficient; the upper end voltage V B of the second low-process-sensitivity zero-temperature-resistance string L2 is less than the upper end voltage V C of the first low-process-sensitivity zero-temperature-resistance string L1; specifically, the second low-process-sensitivity zero-temperature-resistance string L2 comprises a third resistance R3 and a fourth resistance R4; the resistance value of the third resistance R3 changes less with process deviation, and the resistance value of the third resistance R3 increases with temperature rise; the upper end of the third resistance R3 is connected to the drain of the third MOS tube M3 and the upper end of the fourth resistance R4, and the lower end of the third resistance R3 is connected to the lower end of the fourth resistance R4 and the GND potential; the resistance value of the fourth resistance R4 changes less with process deviation, and the resistance value of the fourth resistance R4 decreases with temperature rise; the upper end of the fourth resistance R4 is connected to the drain of the third MOS tube M3 and the upper end of the third resistance R3, and the lower end of the fourth resistance R4 is connected to the lower end of the third resistance R3 and the GND potential. The third low-process-sensitivity zero-temperature-resistance string L3 is used to generate a current that does not change with temperature and has a zero temperature coefficient, and specifically, the third low-process-sensitivity zero-temperature-resistance string L3 includes a seventh resistor R7 and an eighth resistor R8, the resistance value of the seventh resistor R7 changes little with process deviation, the resistance value of the seventh resistor R7 rises with the rise of temperature, an upper end of the seventh resistor R7 is connected to a source end of the fifth MOS tube M5 and an inverting input terminal of the error amplifier, and a lower end of the seventh resistor R7 is connected to a lower end of the eighth resistor R8 and a GND potential, the resistance value of the eighth resistor R8 changes little with process deviation, the resistance value of the eighth resistor R8 falls with the rise of temperature, and a lower end of the eighth resistor R8 is connected to the source end of the fifth MOS tube M5 and the inverting input terminal of the error amplifier.

3. A process variation auto-calibration circuit for a voltage reference source as claimed in claim 1 or 2, characterized in that: The high-process-sensitivity zero-temperature-resistance string H1 is used to generate a voltage that changes greatly with process deviation and has a zero temperature coefficient, and specifically, the high-process-sensitivity zero-temperature-resistance string H1 includes a fifth resistor R5 and a sixth resistor R6, the resistance value of the fifth resistor R5 changes greatly with process deviation, the resistance value of the fifth resistor R5 rises with the rise of temperature, an upper end of the fifth resistor R5 is connected to a drain end of the fourth MOS tube M4, and a lower end of the fifth resistor R5 is connected to an upper end of the sixth resistor R6, the resistance value of the sixth resistor R6 changes greatly with process deviation, the resistance value of the sixth resistor R6 rises with the rise of temperature, an upper end of the sixth resistor R6 is connected to the lower end of the fifth resistor R5, and a lower end of the sixth resistor R6 is connected to a GND potential.

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