High-precision temperature sensor based on resistor temperature sensing front end

Abstract

The invention provides a high-precision temperature sensor based on a resistor temperature-sensing front end, which comprises a temperature-sensing network, a comparison module and a control module, and is characterized in that the temperature-sensing network is used for sampling current flowing through a temperature-sensing resistor and voltage at two ends of the temperature-sensing resistor, and generating ramp signals with different rising slopes at different temperatures; the comparison module is used for comparing the ramp signal generated by the temperature sensing network with the voltage at the two ends of the temperature sensing resistor RT; the control module is used for controlling on-off of the circuit, generating timing time and receiving a trimming signal. According to the high-precision temperature sensor, the temperature sensing resistor integrated in the chip is used for temperature detection under the condition that the high-precision temperature sensor does not depend on the BiCMOS technology, the structure of combining the self-calibration comparator and the pre-comparator is adopted, the overall circuit structure effectively overcomes the defect that a traditional CMOS temperature sensor is high in technology sensitivity, and the reliability of the temperature sensor is improved. The temperature sensor is higher in integration level and temperature sensing precision and lower in power consumption and calibration cost.

Description

Technical Field

[0001] The present invention relates to the field of circuits, and particularly to a high-precision temperature sensor based on a resistance temperature sensing front end. Background Art

[0002] In modern industry and scientific research, high-precision temperature measurement is crucial. As a key measurement device, temperature sensors are widely used in fields such as environmental monitoring, medical equipment, industrial control, and scientific research experiments.

[0003] In existing sensor technologies, a BJT is generally used as the temperature sensing device for the temperature sensing front end, with poor linearity and always having high-order terms in the temperature coefficient; there are mismatches on a single wafer, making the parameters of each chip slightly different, and calibration is often required. The complex calibration process will significantly increase costs; there may be multiple temperature sensor modules on the chip, which requires the temperature sensor to have a small area and low power consumption to improve the overall integration. Summary of the Invention

[0004] The present invention provides a high-precision temperature sensor based on a resistance temperature sensing front end to solve problems such as low temperature sensing accuracy, high cost, and poor integration of traditional temperature sensor architectures.

[0005] The technical solution for achieving the object of the present invention is as follows:

[0006] A high-precision temperature sensor based on a resistance temperature sensing front end includes a temperature sensing network, a comparison module, and a control module; wherein:

[0007] The temperature sensing network is used to sample the current flowing through the temperature sensing resistor and the voltage across the temperature sensing resistor to generate a ramp signal with different rising slopes at different temperatures;

[0008] The comparison module is used to compare the ramp signal generated by the temperature sensing network with the voltage across the temperature sensing resistor;

[0009] The control module is used to control the switch of the circuit, generate a timing time, and receive a trimming signal.

[0010] Compared with the prior art, the beneficial effects of the present invention are:

[0011] The present invention designs a high-precision temperature sensor that does not rely on BiCMOS technology. This temperature sensor uses an RC network with a high temperature-sensing linearity composed of a temperature-sensitive resistor and a MIM capacitor, and uses a TDC to convert the time signal into a digital value. The temperature-sensitive resistor uses an approximate combination of resistors to finely adjust the temperature coefficient, and compensates the temperature coefficient of the timing MIM capacitor array, resulting in high linearity and ultra-high precision. It uses an innovative architecture to suppress current mismatch, with low calibration cost, and can achieve extremely high temperature-sensing accuracy only through batch calibration. The architecture is compact and simple, with a small scale. The circuit first performs a pre-comparison and then enables a self-calibrating comparator, reducing the overall power consumption by several times. And its circuit structure does not involve a bandgap reference voltage source or a BJT-based temperature-sensing circuit, so this temperature sensor can be applied to processes that are not compatible with BJTs. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only a part of the embodiments of the present invention, rather than all the embodiments. For those of ordinary skill in the art, without creative efforts, other drawings obtained based on these drawings all belong to the scope of protection of the present invention.

[0013] Figure 1 It is a simplified core circuit of a high-precision temperature sensor based on a resistance temperature-sensing front end of the present invention.

[0014] Figure 2 It is the circuit operation flow of the present invention.

[0015] Figure 3 It is the trimming resistor network structure of the present invention.

[0016] Figure 4 It is the simulation diagram of the temperature-sensing error of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further elaborates on the present invention in conjunction with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0018] The present invention provides a design of a high-precision temperature sensor based on a resistance temperature-sensing front end, including a temperature-sensing network, a comparison module, and a control module;

[0019] The temperature-sensing network is used to sample the current flowing through the temperature-sensitive resistor and the voltage across the temperature-sensitive resistor, and generate a ramp signal with different rising slopes at different temperatures;

[0020] The described comparison module is used to compare the ramp signal generated by the temperature sensing network with the voltage across the temperature sensing resistor R stored in the first capacitor C1 T at both ends;

[0021] The described control module is used to control the switch of the circuit, generate the timing time, and receive the trimming signal.

[0022] The temperature sensing network includes: a first resistor R1, a second resistor R2, a third resistor R3, a temperature sensing resistor R T , a timing capacitor C, a first capacitor C1, a second capacitor C2, a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a fifth switch S5, an operational amplifier OP, a first PMOS transistor M1, and a second PMOS transistor M2. A cascode current source with a high output impedance is formed by using the first MOS transistor M1 and the second MOS transistor M2. The gate voltage of the second MOS transistor M2 is constantly KVDD. The first capacitor C1 is used to store the voltage across the temperature sensing resistor when the second switch S2 is turned on. This voltage is compared with the voltage on the timing capacitor C through a comparator during the timing conversion period. The second capacitor C2 is used to store the gate voltage of the current source after the temperature sensing network is stabilized. During the RC timing stage, this current charges the second capacitor C2. The operational amplifier OP adopts a five-transistor OTA structure and is used to establish a negative feedback circuit during the temperature sensing process. The described cascode current source eliminates the mismatch of the traditional current mirror. The cascode structure and low gate transconductance reduce the current deviation. By storing the temperature sensing current through the current source, the current deviation of the traditional current mirror replication is eliminated, achieving high-precision temperature sensing.

[0023] The upper end of the first resistor R1 is connected to the power supply VDD, and the lower end is connected to the upper end of the second resistor R2, the negative input terminal of the operational amplifier OP, and the gate of the second PMOS transistor M2. The voltage at this point is KVDD.

[0024] The upper end of the second resistor R2 is connected to the lower end of the first resistor R1, the negative input terminal of the operational amplifier OP, and the gate of the second PMOS transistor M2. The lower end of the second resistor R2 is connected to the upper end of the third resistor R3 and the negative input terminal of the pre-comparator. The voltage at this point is Pre-compare. The upper end of the third resistor R3 is connected to the lower end of the second resistor R2 and the negative input terminal of the pre-comparator, and the lower end is connected to GND.

[0025] The temperature sensing resistor R T has its lower end connected to GND and its upper end connected to the second switch S2, the third switch S3, and the positive input terminal of the operational amplifier.

[0026] The lower end of the timing capacitor C is connected to GND, and the upper end is connected to the fourth switch S4, the fifth switch S5, the positive input terminal of the self-calibration comparator, and the positive input terminal of the pre-comparator.

[0027] The lower end of the first capacitor C1 is connected to GND, and the upper end is connected to the second switch S2 and the negative input terminal of the self-calibration comparator. The voltage at this point is KVDD_duplicate.

[0028] The upper end of the second capacitor C2 is connected to VDD, and the lower end is connected to the first switch S1 and the gate of the first PMOS transistor.

[0029] One end of the first switch S1 is connected to the output terminal of the operational amplifier OP, and the other end is connected to the lower end of the second capacitor C2 and the gate of the first PMOS transistor.

[0030] One end of the second switch S2 is connected to the upper end of the first capacitor C1 and the negative input terminal of the self-calibration comparator, and the other end is connected to the third switch S3, the positive input terminal of the operational amplifier OP, and the upper end of the temperature-sensitive resistor R T of.

[0031] One end of the third switch S3 is connected to the positive input terminal of the operational amplifier OP, the second switch S2, and the upper end of the temperature-sensitive resistor R T of, and the other end is connected to the drain of the second PMOS transistor M2.

[0032] One end of the fourth switch S4 is connected to the upper end of the timing capacitor C, the fifth switch S5, the positive input terminal of the self-calibration comparator, and the positive input terminal of the pre-comparator. The voltage at this point is V C , and the other end is connected to the drain of the second PMOS transistor M2.

[0033] One end of the fifth switch S5 is connected to GND, and the other end is connected to the fourth switch S4, the upper end of the timing capacitor C, the positive input terminal of the self-calibration comparator, and the positive input terminal of the pre-comparator.

[0034] The negative input terminal of the operational amplifier OP is connected to the lower end of the first resistor R1, the upper end of the second resistor R2, and the gate of the second PMOS transistor. The positive input terminal is connected to the second switch S2, the third switch S3, and the upper end of the temperature-sensitive resistor R T of, and the output terminal is connected to the first switch S1.

[0035] The source of the first PMOS transistor M1 is connected to VDD, the gate is connected to the first switch S1 and the lower end of the second capacitor, and the drain is connected to the source of the second PMOS transistor.

[0036] The source of the second PMOS transistor M2 is connected to the drain of the first PMOS transistor M1, and the gate is connected to the lower end of the first resistor R1, the upper end of the second resistor R2, and the negative input terminal of the operational amplifier OP.

[0037] The timing capacitor C is a MIM capacitor, which has good voltage linearity and extremely low temperature coefficient, while R T as a temperature-sensitive resistor is sensitive to temperature changes, R TTwo resistor combinations are adopted, and 12-bit trimming is performed at the temperature-sensitive resistor. The sum of the two resistor values is used to obtain the total temperature-sensitive resistor value to offset the non-linearity caused by the high-order temperature coefficient of the resistor, thereby reducing the temperature error. In this design, the temperature is linearly converted into the timing time, and the timing time value is R T ·C.

[0038] The comparison module includes a pre-comparator and a self-calibrating comparator. The self-calibrating comparator adopts a folded cascode structure. Due to its differential structure, the voltage comparator is always accompanied by an input offset voltage, which causes the converted temperature value to deviate from the actual value. This design proposes a self-calibration design based on switched capacitors for the front end of the temperature-sensitive circuit used. Specifically:

[0039] The negative input terminal of the pre-comparator is connected to the lower end of the second resistor R2 and the upper end of the third resistor R3. The positive input terminal is connected to the positive input terminal of the self-calibrating comparator, the upper end of the timing capacitor C, the fourth switch S4, and the fifth switch S5. The output terminal is connected to the control module.

[0040] The negative input terminal of the self-calibrating comparator is connected to the second switch S2 and the upper end of the first capacitor C1. The positive input terminal is connected to the positive input terminal of the pre-comparator, the upper end of the timing capacitor C, the fourth switch S4, and the fifth switch S5. The output terminal and the enable terminal are connected to the control module.

[0041] The self-calibrating comparator has a high comparison speed to achieve high precision, which requires a large current consumption. Therefore, a pre-comparator is used for preliminary judgment to reduce the current consumption;

[0042] After the self-calibration is completed, the comparator enters the comparison state through the comparison enable signal. At this time, the positive and negative input terminals of the comparator are disconnected and connected to the capacitor array, and the output terminal is disconnected from the offset storage capacitor and connected to the inverter buffer stage. The comparison result is converted into a digital signal after two-stage buffering.

[0043] The control module is used to control the on and off of the switches in the circuit; to output the digital value of the temperature-sensitive signal; to receive the trimming signal and control the working state of the switches connected in parallel to the temperature-sensitive resistor in the temperature-sensitive network.

[0044] The control module is respectively connected to the output terminal and the enable terminal of the self-calibrating comparator, the output terminal of the pre-comparator, the temperature-sensitive network of the temperature-sensitive resistor R T and the control terminals of the first switch S1 to the fifth switch S5. On the one hand, it receives the reference clock signal Referenceclock and the trimming signal Trim and outputs the temperature-sensitive signal OUT. On the other hand, it controls the on and off of the first switch S1 to the fifth switch S5 and the trimming amount of the temperature-sensitive network of the temperature-sensitive resistor R T ;

[0045] Thermistor R T Adopts a composite structure of a programmable switch array and a segmented resistor unit, including: 12 reference resistor units (W0 - W11), 12 PMOS trimming switches, and a basic reference resistor unit W BASE , the first redundant structure DummyP, and the second redundant structure Dummy N.

[0046] One end of the first redundant structure Dummy P is connected to the port RP of the thermistor R T , and the other end is connected to a resistor structure formed by connecting 12 reference resistor units (W0 - W11) in series. Each resistor unit is connected in parallel with a PMOS trimming switch, and the control terminals of the switches are respectively connected to independent bit control signal lines bit 0 to bit 11. The basic reference resistor unit W BASE is connected to the last reference resistor unit W11, and the other end of the basic reference resistor unit W BASE is connected to the second redundant structure Dummy N, and the other end of the second redundant structure DummyN is connected to the port RN of the thermistor R T . The reference resistor units (W0 - W11) and the basic reference resistor unit W BASE are both formed by combining two resistors in series in the same proportion, and only differ in the resistance value. The redundant structure is composed of reference resistor units short - circuited by wires at both ends.

[0047] Embodiment 1

[0048] Refer to Figure 1 As shown, a simplified circuit of the core of a high - precision temperature sensor based on a resistive temperature - sensing front - end. The shown simplified circuit has two working states, including a loop - establishment sampling state and an RC timing state. In the loop - establishment state, the first switch S1, the second switch S2, the third switch S3, and the fifth switch S5 are turned on, the fourth switch S4 is turned off, and the operational amplifier OP, the first PMOS transistor M1, the second PMOS transistor M2, and the thermistor R T constitute a current - sampling circuit, loop - sampling the current I passing through the thermistor R T and storing the gate voltage of the first PMOS transistor M1 at this time on the second capacitor C2. Due to the existence of the operational - amplifier offset voltage, in the steady state, the current I can be expressed as

[0049]

[0050] where, KVDD_duplicate≈KVDD. It can be seen that although the voltage value finally loaded on the thermistor is not strictly equal to KVDD, KVDD is the voltage for the thermistor R TA rough voltage is provided. Additionally, since the actual voltage range of the current source output node is from 0V to KVDD, the highest voltage value of this node is KVDD, which is the same as the bias voltage of the second PMOS transistor M2. Therefore, the cascode current source formed by the first PMOS transistor M1 and the second PMOS transistor M2 always operates in the saturation region. The voltage actually applied across the temperature-sensitive resistor is stored on the first capacitor C1 through the second switch S2, which ensures that the reference voltage during the subsequent comparator flip is the true voltage value across the temperature-sensitive resistor.

[0051] After the loop stabilizes, the circuit enters the RC timing state. In the RC timing state, the first switch S1, the second switch S2, the third switch S3, and the fifth switch S5 are turned off and the fourth switch S4 is turned on, and the circuit starts timing. The voltage V across the capacitor C starts rising from 0V and the comparator flips when it reaches KVDD_duplicate, and the timing ends. The timing time t is

[0052]

[0053] The operating principle of the circuit is referred to Figure 2 as shown, and finally the expression of temperature and timing time is obtained

[0054]

[0055] where T0 is 27°C, k is the temperature coefficient of the temperature-sensitive resistor R T , ΔT is the difference between the temperature T and 27°C, and t0 is the timing time when the ambient temperature is 27°C.

[0056] This design linearly converts temperature into timing time. The timing time value is R T ·C, where C is the MIM capacitor, which has good voltage linearity and an extremely low temperature coefficient, while R T acts as the temperature-sensitive resistor and is sensitive to temperature changes.

[0057] This design selects the MIM capacitor C as the timing capacitor. This capacitor has excellent linearity and almost no temperature coefficient. Even so, its weak temperature coefficient will still cause a certain error. In this design, the higher-order non-linear part of the above two temperature-sensitive resistors is used to offset the temperature coefficient of the capacitor. The specific implementation method is to finely adjust the ratio of the two resistors to generate different temperature coefficient "radian". Among them, the "radian" of the resistor is opposite to the "radian" of the MIM capacitor, and the two can be approximately offset each other. Finally, through fine-tuning of the resistor parameters, the optimal parameters are determined to minimize the overall temperature coefficient change of the RC temperature-sensitive network.

[0058] The comparison module includes a self-calibrating comparator and a pre-comparator. In this design, a pre-comparator is used for preliminary judgment. When the voltage of the timing capacitor rises to about 90% of the comparison voltage, the high-precision comparator is activated to participate in the temperature conversion. The circuit first performs pre-comparison and then enables the self-calibrating comparator, reducing the overall power consumption by several times.

[0059] In this design, the temperature value is corrected by trimming the resistance value, that is, correcting the resistance value R in t0 = R T0 ·C. Only single-point batch calibration is required, and the calibration cost is low. This design uses a 12-bit temperature-sensing network with a trimming accuracy of <±0.1°C. The structure of the trimming resistor network is referred to T0 as shown. Figure 3 as shown.

[0060] As Figure 4 shown, the maximum temperature-sensing error of the circuit is no more than 0.26°C in the temperature range of -40°C to 125°C, with high temperature-sensing accuracy.

[0061] Without relying on the BiCMOS process, the high-precision temperature sensor of this application uses the temperature-sensing resistors integrated inside the chip for temperature detection, and adopts the structure of a combination of a self-calibrating comparator and a pre-comparator. The overall circuit structure effectively overcomes the defect of high process sensitivity existing in traditional CMOS temperature sensors, and has higher integration, temperature-sensing accuracy, lower power consumption and calibration cost.

[0062] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high-precision temperature sensor based on a resistance temperature sensing front end, characterized in that: It includes a temperature sensing network, a comparison module and a control module; wherein: The temperature sensing network is used to sample the current flowing through the temperature sensing resistor and the voltage across the temperature sensing resistor to generate a ramp signal with different rising slopes at different temperatures; The comparison module is used to compare the ramp signal generated by the temperature sensing network with the voltage across the temperature sensing resistor; The control module is used to control the switch of the circuit, generate the timing time, and receive the adjustment signal.

2. A high-precision temperature sensor based on a resistance temperature sensing front end according to claim 1, characterized in that: The temperature sensing network includes: a first resistor (R1), a second resistor (R2), a third resistor (R3), a temperature sensing resistor (R T ), a timing capacitor (C), a first capacitor (C1), a second capacitor (C2), a first switch (S1), a second switch (S2), a third switch (S3), a fourth switch (S4), a fifth switch (S5), an operational amplifier (OP), a first PMOS tube (M1) and a second PMOS tube (M2), wherein the first PMOS tube (M1) and the second PMOS tube (M2) constitute a common source and common gate current source with a high output impedance, the gate voltage of the second PMOS tube (M2) is constant to KVDD, the first capacitor (C1) is used to store the voltage across the temperature sensing resistor when the second switch (S2) is turned on, and the voltage is compared with the voltage on the timing capacitor (C) through a comparator during a timing conversion cycle; the second capacitor (C2) is used to store the gate voltage of the current source after the temperature sensing network is stable, and the current charges the second capacitor (C2) during the RC timing stage, and the operational amplifier (OP) adopts a five-tube OTA structure, which is used to establish a negative feedback circuit during the temperature sensing process.

3. A high-precision temperature sensor based on a resistance temperature sensing front end according to claim 2, characterized in that: The timing capacitor (C) is a MIM capacitor, and the temperature sensing resistor (R T ) Use a combination of two resistors and perform a 12-bit adjustment on the temperature-sensing resistor. The total temperature-sensing resistor value is obtained by adding the two resistor values.

4. A high-precision temperature sensor based on a resistance temperature sensing front end according to claim 3, characterized in that: The temperature sensing resistor (R T ) adopts a composite structure of a programmable switch array and a segmented resistor unit, specifically including: 12 reference resistor units, 12 PMOS trimming switches, a basic reference resistor unit, a first redundant structure (Dummy P) and a second redundant structure (Dummy N); one end of the first redundant structure (Dummy P) is connected to a temperature-sensitive resistor (R T ) port RP, the other end of which is connected to a resistance structure composed of 12 reference resistance units connected in series, wherein each resistance unit is connected in parallel with a PMOS trimming switch, and each switch control end is correspondingly connected to an independent bit control signal line bit 0 to bit 11, the basic reference resistance unit is connected to the last reference resistance unit, and the other end of the basic reference resistance unit is connected to the second redundant structure (DummyN), and the other end of the second redundant structure (DummyN) is connected to the temperature sensing resistor (R T ) port RN.

5. A high-precision temperature sensor based on a resistance temperature sensing front end according to claim 4, characterized in that: The reference resistance unit and the basic reference resistance unit are both formed by combining two resistors in the same proportion and connected in series, and the redundant structure is composed of reference resistance units with two ends short-circuited by wires.

6. A high-precision temperature sensor based on a resistance temperature sensing front end according to claim 2, characterized in that: The comparison module includes a pre-comparator and a self-calibration comparator. The self-calibration comparator adopts a folded common source and common gate structure. The voltage comparator has a differential structure. The negative input terminal of the pre-comparator is connected to the lower end of the second resistor (R2) and the upper end of the third resistor (R3), the positive input terminal is connected to the positive input terminal of the self-calibration comparator, the upper end of the timing capacitor (C), the fourth switch (S4) and the fifth switch (S5), and the output terminal is connected to the control module; The negative input terminal of the self-calibration comparator is connected to the second switch (S2) and the upper end of the first capacitor (C1), the positive input terminal is connected to the positive input terminal of the pre-comparator, the upper end of the timing capacitor (C), the fourth switch (S4) and the fifth switch (S5), and the output terminal and the enable terminal are connected to the control module.

7. A high-precision temperature sensor based on a resistance temperature sensing front end according to claim 6, characterized in that: The circuit of the temperature sensing network is: The upper end of the first resistor (R1) is connected to the power supply VDD, and the lower end is connected to the upper end of the second resistor (R2) and the negative input end of the operational amplifier (OP) and the gate of the second PMOS tube (M2), and the voltage at this point is KVDD; The upper end of the second resistor (R2) is connected to the lower end of the first resistor (R1), the negative input end of the operational amplifier (OP), and the gate of the second PMOS tube (M2); the lower end of the second resistor (R2) is connected to the upper end of the third resistor (R3) and the negative input end of the pre-comparator, and the voltage at this point is Pre-compare; the upper end of the third resistor (R3) is connected to the lower end of the second resistor (R2) and the negative input end of the pre-comparator, and the lower end is connected to GND; The temperature sensing resistor (R T ) has a lower end connected to GND, and an upper end connected to the second switch (S2), the third switch (S3) and the positive input terminal of the operational amplifier; The lower end of the timing capacitor (C) is connected to GND, and the upper end is connected to the fourth switch (S4), the fifth switch (S5), the positive input end of the self-calibration comparator and the positive input end of the pre-comparator; The lower end of the first capacitor (C1) is connected to GND, and the upper end is connected to the second switch (S2) and the negative input end of the self-calibration comparator, and the voltage at this point is KVDD_duplicate; The upper end of the second capacitor (C2) is connected to VDD, and the lower end is connected to the first switch (S1) and the gate of the first PMOS tube; One end of the first switch (S1) is connected to the output end of the operational amplifier (OP), and the other end is connected to the lower end of the second capacitor (C2) and the gate of the first PMOS tube; One end of the second switch (S2) is connected to the upper end of the first capacitor (C1) and the negative input end of the self-calibration comparator, and the other end is connected to the third switch (S3), the positive input end of the operational amplifier (OP) and the temperature sensing resistor (R T ) One end of the third switch (S3) is connected to the positive input end of the operational amplifier (OP), the second switch (S2) and the temperature sensing resistor (R T ), and the other end is connected to the drain of the second PMOS tube (M2); One end of the fourth switch (S4) is connected to the upper end of the timing capacitor (C), the fifth switch (S5), the positive input end of the self-calibration comparator and the positive input end of the pre-comparator, and the voltage at this point is V C , the other end is connected to the drain of the second PMOS tube (M2); One end of the fifth switch (S5) is connected to GND, and the other end is connected to the fourth switch (S4), the upper end of the timing capacitor (C), the positive input end of the self-calibration comparator and the positive input end of the pre-comparator; The negative input end of the operational amplifier (OP) is connected to the lower end of the first resistor (R1), the upper end of the second resistor (R2) and the gate of the second PMOS tube, and the positive input end is connected to the second switch (S2), the third switch (S3) and the temperature sensing resistor (R T ), the output end is connected to the first switch (S1); The source of the first PMOS tube (M1) is connected to VDD, the gate is connected to the first switch (S1) and the lower end of the second capacitor, and the drain is connected to the source of the second PMOS tube; The source of the second PMOS tube (M2) is connected to the drain of the first PMOS tube (M1), and the gate is connected to the lower end of the first resistor (R1), the upper end of the second resistor (R2) and the negative input end of the operational amplifier (OP).

8. A high-precision temperature sensor based on a resistance temperature sensing front end according to claim 6, characterized in that: The control module is respectively connected to the output end and the enable end of the self-calibration comparator, the output end of the pre-comparator, and the temperature sensing resistor (R T ) is connected to the temperature sensing network and the control ends of the first switch (S1) to the fifth switch (S5).

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