Calibration-free high-precision temperature sensor

Abstract

The invention relates to a calibration-free high-precision temperature sensor, which belongs to the technical field of digital-analog hybrid integrated circuits, and comprises a temperature current generation module which comprises an ICTAT current branch and an IPTAT current branch which are respectively used for generating current positively correlated with temperature and current negatively correlated with temperature; the integrating capacitor is connected with the ICTAT current branch and the IPTAT current branch through a charge pump switch; the first end of the comparator inputs integrating capacitor voltage, and the second end inputs reference voltage; the set end of the RS trigger is connected with the output end of the comparator, and a clock signal is accessed to the reset end of the RS trigger; the counter is connected with the Q end of the RS trigger and is used for carrying out downsampling counting on the output of the Q end of the RS trigger and outputting; wherein the charge pump switch is controlled according to the output of the Q end of the RS trigger; a base compensation resistor is arranged in an IPTAT current branch of the temperature current generation module and used for eliminating nonlinear errors caused by limited current gain of a bipolar transistor.

Description

Technical Field

[0001] This invention belongs to the field of temperature sensor technology, specifically relating to a calibration-free high-precision temperature sensor. Background Technology

[0002] Sensors serve as a bridge between the physical and information worlds. Temperature sensors, as tools for temperature measurement and control, play a vital role in modern industry. Temperature sensors can be categorized into discrete and integrated types based on their integration level. Discrete sensors, implemented using discrete components, are large, expensive, and difficult to apply in situations requiring high integration levels. Integrated CMOS temperature sensors, on the other hand, are widely used in industry due to their small size, low cost, and ability to directly convert analog signals to digital signals. The basic structural block diagram of a CMOS temperature sensor is shown below. Figure 1 As shown, the input binary code has the same number of bits as its conversion bit. The binary input code represents digital codes with different weights, which control the switches at different positions in the weighting network, putting them in an on or off state. This weight can be implemented by means of resistors, current, etc. Finally, the selected output is connected to an analog amplifier to output an analog signal.

[0003] Common temperature sensor architectures can be categorized by electrical properties into voltage / current type temperature sensors, and by signal characteristics into time-domain / frequency-domain type temperature sensors. Voltage / current type temperature sensors offer good stability and high accuracy, but often require significant circuit overhead. Frequency-domain / time-domain type temperature sensors have higher process compatibility, but the time-domain conversion scheme requires a larger area, and the frequency-domain readout scheme suffers from larger temperature measurement errors due to circuit nonlinearity and other issues, requiring additional calibration. Therefore, a calibration-free and high-precision temperature sensor is needed. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides a calibration-free, high-precision temperature sensor. The technical problem to be solved by this invention is achieved through the following technical solution: This invention provides a calibration-free high-precision temperature sensor, comprising: a temperature current generation module, including I... CTAT Current branch and I PTAT The current branches are used to generate a temperature-dependent coefficient. Current and negatively correlated with temperature Current; integrating capacitor, connected to I via charge pump switch CTAT Current branch and the I PTATThe circuit includes a current branch; a comparator, with the voltage of the integrating capacitor input at the first terminal and a reference voltage input at the second terminal; an RS flip-flop, with the set terminal connected to the output of the comparator and the reset terminal connected to a clock signal; a counter, connected to the Q terminal of the RS flip-flop, used to downsample and count the output of the Q terminal of the RS flip-flop and then output the counter; wherein, the charge pump switch is controlled according to the output of the Q terminal of the RS flip-flop; and the temperature current generation module's I... PTAT A base compensation resistor is provided in the current branch to eliminate the nonlinear error caused by the finite current gain of the bipolar transistor.

[0005] In one embodiment of the present invention, the I CTAT Current branch and I PTAT The current branches are connected in parallel, and the I PTAT The base of the bipolar transistor Q2 in the current branch is connected to the base compensation resistor R. βb Grounding.

[0006] In one embodiment of the present invention, the temperature current generation module includes: a MOSFET M P1 MOSFET M P2 MOSFET M P3 MOSFET M P4 MOSFET M N1 Resistors R1, R2, and base compensation resistor R βb The system comprises: bipolar transistor Q1, bipolar transistor Q2, bipolar transistor Q3, charge pump switch SW1, comparator A1, and comparator A2; wherein, the MOS transistor M... P1 The MOS transistor M P2 The MOS transistor M P3 and the MOS transistor M P4 The sources of all are connected to the power supply terminal, and the MOS transistor M P1 The MOS transistor M P2 The MOS transistor M P3 The gate of the MOSFET is connected to the output of the comparator A1; the MOSFET M P1 The drain of the resistor is connected to the first terminal of the resistor R1 and the non-inverting input terminal of the comparator A1, respectively. The inverting input terminal of the comparator A1 is connected to the MOS transistor M. P2 The drain of the MOSFET and the emitter of the bipolar transistor Q2; the MOS transistor M P3 The drain of the bipolar transistor Q3 is connected to the emitter of the bipolar transistor Q3 and the non-inverting input of the comparator A2, respectively; the second end of the resistor R1 is connected to the emitter of the bipolar transistor Q1, and the base and collector of the bipolar transistor Q1 are both grounded; the base of the bipolar transistor Q2 is connected to the base compensation resistor R. βbThe first terminal, the collector of the bipolar transistor Q2 and the base compensation resistor R βb The second terminal of each is grounded, and the base compensation resistor R βb A charge pump switch SW1 is connected across the top; the base and collector of the bipolar transistor Q3 are both grounded; the MOS transistor M N1 The base of the transistor is connected to the output of comparator A2, and the source is connected to the inverting input of comparator A2 and the first terminal of resistor R2, with the second terminal of resistor R2 grounded; the MOS transistor M... P4 Drain output Current, the MOS transistor M N1 Drain output Electric current.

[0007] In one embodiment of the present invention, the Current and with the Current ratio The expression is: ; in, The current ratio is... It is a constant and independent of temperature.

[0008] In one embodiment of the present invention, the base compensation resistor R βb The expression for the resistance value is: ; in, The base compensation resistor R βb The resistance value; The voltage difference between the base and emitter of the bipolar transistor Q1 and the bipolar transistor Q2; This is the base-emitter voltage of the bipolar transistor Q3; Boltzmann's constant; Thermodynamic temperature; The charge of an electron; This is the transistor saturation current; It is a natural constant.

[0009] In one embodiment of the present invention, the expression for the output value of the counter is: ; in, for The discharge time of the current; for Charging time of the current.

[0010] In one embodiment of the present invention, the average charge of the integrating capacitor is 0 over multiple time periods.

[0011] In one embodiment of the present invention, the charge pump switch is output from the Q terminal of the RS flip-flop. Control, when the Q output of the RS flip-flop... When it is high, the The current charges the integrating capacitor; when the Q output of the RS flip-flop... When it is low, the The current discharges the integrating capacitor.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: The calibration-free high-precision temperature sensor of the present invention, through the I in the temperature current generation module PTAT By introducing a base compensation resistor in the current branch, the nonlinear error caused by the finite current gain of the bipolar transistor is fundamentally eliminated, achieving high linearity of the sensor core and improving the accuracy of the temperature sensor. It also utilizes the charge balance principle to directly convert temperature-related analog quantities into linear digital outputs. Furthermore, it eliminates the complex calibration circuits or digital post-processing algorithms relied upon by traditional high-precision temperature sensors, eliminating the need for additional calibration. While maintaining high measurement accuracy, it significantly reduces chip area and testing costs, making it particularly suitable for large-scale IoT devices with stringent requirements for cost and integration.

[0013] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0014] Figure 1 This is a structural block diagram of an existing temperature sensor; Figure 2 This is an architectural diagram of the calibration-free high-precision temperature sensor provided in an embodiment of the present invention; Figure 3 The I-type resistor provided in this embodiment of the invention employs a compensation resistor. CTAT and I PTAT Generate circuit diagram; Figure 4 This is a timing logic diagram of the calibration-free high-precision temperature sensor provided in an embodiment of the present invention; Figure 5 This is a temperature-digital code first-order fitting curve of the uncalibrated high-precision temperature sensor provided in this embodiment of the invention. Detailed Implementation

[0015] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description of a calibration-free high-precision temperature sensor based on the present invention is provided in conjunction with the accompanying drawings and specific embodiments.

[0016] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a more in-depth and concrete understanding can be gained of the technical means and effects adopted by the present invention to achieve its intended purpose. However, the accompanying drawings are for reference and illustration only and are not intended to limit the technical solutions of the present invention.

[0017] Example 1 like Figure 2 As shown, Figure 2 This is an architecture diagram of a calibration-free high-precision temperature sensor provided in an embodiment of the present invention, wherein CMP is a comparator and CNT is a counter.

[0018] In this embodiment, the uncalibrated high-precision temperature sensor includes: a temperature current generation module, an integrating capacitor, a comparator, an RS flip-flop, and a counter. The temperature current generation module includes I... CTAT Current branch and I PTAT The current branches are used to generate a temperature-dependent coefficient. Current and negatively correlated with temperature Current; the integrating capacitor is connected to I via a charge pump switch. CTAT Current branch and I PTAT The current branch; the comparator's first terminal receives the voltage of the integrating capacitor, and its second terminal receives the reference voltage; the RS flip-flop's set terminal is connected to the comparator's output, and its reset terminal receives the clock signal; the counter is connected to the RS flip-flop's Q terminal, used to downsample and count the output of the RS flip-flop's Q terminal and then output the counter; the charge pump switch is controlled according to the output of the RS flip-flop's Q terminal; the temperature current generation module's I... PTAT A base compensation resistor is provided in the current branch to eliminate the nonlinear error caused by the finite current gain of the bipolar transistor.

[0019] In one optional implementation, I CTAT Current branch and I PTAT Current branches are connected in parallel, I PTAT The base of bipolar transistor Q2 in the current branch is connected to the base compensation resistor R. βb Grounding.

[0020] Specifically, such as Figure 3 As shown, Figure 3 The I-type resistor provided in this embodiment of the invention employs a compensation resistor. CTAT and IPTAT Circuit diagram for temperature and current generation. The temperature and current generation module includes: MOSFET M P1 MOSFET M P2 MOSFET M P3 MOSFET M P4 MOSFET M N1 Resistors R1, R2, and base compensation resistor R βb Bipolar transistors Q1, Q2, and Q3; charge pump switch SW1; comparator A1 and comparator A2; among which, MOSFET M... P1 MOSFET M P2 MOSFET M P3 and MOSFET M P4 The sources of all transistors are connected to the power supply, and the MOSFET M P1 MOSFET M P2 MOSFET M P3 The gate of the MOSFET is connected to the output of comparator A1; MOSFET M P1 The drain of the circuit is connected to the first terminal of resistor R1 and the non-inverting input terminal of comparator A1, respectively. The inverting input terminal of comparator A1 is connected to MOSFET M. P2 The drain of the MOSFET and the emitter of the bipolar transistor Q2; MOSFET M P3 The drain of transistor Q1 is connected to the emitter of bipolar transistor Q3 and the non-inverting input of comparator A2, respectively; the second end of resistor R1 is connected to the emitter of bipolar transistor Q1, and the base and collector of bipolar transistor Q1 are both grounded; the base of bipolar transistor Q2 is connected to the base compensation resistor R. βb The first terminal is the collector and base compensation resistor R of the bipolar transistor Q2. βb The second terminal is grounded, and the base compensation resistor R βb A charge pump switch SW1 is connected across the top; the base and collector of bipolar transistor Q3 are both grounded; MOSFET M N1 The base of the transistor is connected to the output of comparator A2, and its source is connected to the inverting input of comparator A2 and the first terminal of resistor R2, respectively. The second terminal of resistor R2 is grounded. The MOSFET M... P4 Drain output Current, MOSFET M N1 Drain output Electric current.

[0021] In one optional implementation, Current and Current ratio The expression is: ; in, For current ratio, current ratio It is a constant and independent of temperature.

[0022] In one optional implementation, the expression for the counter's output value is: ; in, for The discharge time of the current; for Charging time of the current.

[0023] In an alternative implementation, a compensation resistor is added between the base of the bipolar transistor Q2 and ground. This can eliminate the current gain of the transistor. right The influence of base compensation resistor R βb The expression for the resistance value is: ; in, Base compensation resistor R βb The resistance value; This is the voltage difference between the base and emitter of bipolar transistors Q1 and Q2; This is the base-emitter voltage of the bipolar transistor Q3; Boltzmann's constant; Thermodynamic temperature; The charge of an electron; This is the transistor saturation current; It is a natural constant.

[0024] In one alternative implementation, the charge pump switch is output from the Q terminal of an RS flip-flop. Control, when the Q output of the RS flip-flop... When it is high level, Current charges the integrating capacitor; when the Q output of the RS flip-flop... When it is low level, The current discharges the integrating capacitor. For example, the average charge of the integrating capacitor is 0 over multiple time periods.

[0025] The principle of the calibration-free high-precision temperature sensor of this invention is as follows: The calibration-free high-precision temperature sensor of this invention can be equivalent to a first-order 1-bit delta-sigma ADC (Analog to Digital Converter). The integrating capacitor C is filled with a current that is positively correlated with temperature. Charging or current that is negatively correlated with temperature Discharge, compare the voltage across the integrating capacitor C. and reference voltage The charge pump switch is controlled based on the comparator output. After multiple cycles of feedback control, the average charge of the integrating capacitor C is 0.

[0026] The charging formula for the integrating capacitor C is: ,in, It is the change in charge; This is the charging current; This refers to charging time; Capacitance; This represents the change in voltage.

[0027] After a sufficiently long time, the average charge of the integrating capacitor C becomes 0, i.e., the amount of charging charge. With discharge charge Equal, that is ;in, The discharge time of the CTAT current; The charging time for the PTAT current. Read the value using a counter within one counting cycle. The number of high-level signals, CNT_OUT, is obtained by normalizing it. Average duty cycle of the entire charge-discharge cycle : .

[0028] Change and If the current ratio is such that the sum of the two is approximately independent of temperature, then a digital output CNT_OUT that is linearly related to temperature can be obtained.

[0029] like Figure 3 As shown, in deep submicron CMOS technology, the base current of a bipolar transistor is not negligible due to its finite current gain. The current gain of the transistor... The mismatch between its base and emitter voltage It has a great influence, making and The sum of the currents deviates from the set value, and the final digital output code It is non-linear with temperature. At this point... The expression is: ; in, Boltzmann's constant; Thermodynamic temperature; The charge of an electron; This is the collector current of the transistor; This is the transistor saturation current; This represents the current gain of the transistor.

[0030] By adding a compensation resistor between the base of the bipolar transistor Q2 and the ground , the current gain of the transistor can be eliminated to , and at this time The expression of is: where is the base-emitter voltage of the bipolar transistor Q3; is the base compensation resistor; is the voltage difference between the bases and emitters of the bipolar transistor Q1 and the bipolar transistor Q2.

[0031] The Q-terminal output of the RS flip-flop is sampled using a high-frequency clock , and the number of high-level outputs is counted using a counter over a sufficiently long period to obtain the counter output value CNT_OUT containing the duty cycle information of the PTAT current, and this value has a linear relationship with temperature. The timing logic diagram of the non-calibrated high-precision temperature sensor of the present invention is shown in Figure 4 as shown Figure 4 and is the timing logic diagram of the non-calibrated high-precision temperature sensor provided by an embodiment of the present invention.

[0032] When the comparator input clock CLK_CMP is low, the comparator is reset and both comparator outputs are low, that is, both the S and R inputs of the RS flip-flop are low and it maintains the previous state; when CLK_CMP reaches the rising edge, if VC > VREF, the positive output of the comparator is high and the negative output is low, and the output of the RS flip-flop is high, controlling the charge pump to switch to the current ICTAT and the capacitor to discharge; if VC < VREF, the positive output of the comparator is low and the negative output is high, and the output of the RS flip-flop is low, controlling the charge pump to switch to the current IPTAT and the capacitor to charge. The counter clock is a high-frequency clock, and the number of high-level samples is counted over a sufficiently long statistical period. is high.

[0033] Within 8192 counting cycles, the count output code is fitted with the actual simulated temperature, and the temperature-digital code primary fitting curve of the non-calibrated high-precision temperature sensor is shown in Figure 5 as shown Figure 5 and is the temperature-digital code primary fitting curve of the non-calibrated high-precision temperature sensor provided by an embodiment of the present invention. It can be seen from the figure that the non-calibrated high-precision temperature sensor of the present invention has a calibration-free temperature error of less than 1.8 °C under the TT process corner and within the temperature range of 0 to 125 °C, and has a high calibration-free accuracy.

[0034] The calibration-free high-precision temperature sensor of the present invention, through the I in the temperature current generation module PTAT By introducing a base compensation resistor in the current branch, the nonlinear error caused by the finite current gain of the bipolar transistor is fundamentally eliminated, achieving high linearity of the sensor core and improving the accuracy of the temperature sensor. It also utilizes the charge balance principle to directly convert temperature-related analog quantities into linear digital outputs. Furthermore, it eliminates the complex calibration circuits or digital post-processing algorithms relied upon by traditional high-precision temperature sensors, eliminating the need for additional calibration. While maintaining high measurement accuracy, it significantly reduces chip area and testing costs, making it particularly suitable for large-scale IoT devices with stringent requirements for cost and integration.

[0035] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that an article or device comprising a list of elements includes not only those elements but also other elements not expressly listed. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device comprising said element. Terms such as "connected" or "linked" are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect. The orientations or positional relationships indicated by terms such as "upper," "lower," "left," and "right" are based on the orientations or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0036] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A calibration-free, high-precision temperature sensor, characterized in that, include: Temperature and current generation module, including I CTAT Current branch and I PTAT The current branches are used to generate a temperature-dependent coefficient. Current and negatively correlated with temperature Current; The integrating capacitor is connected to the I via a charge pump switch. CTAT Current branch and the I PTAT Current branch; The comparator has the voltage of the integrating capacitor input at its first terminal and the reference voltage input at its second terminal. An RS flip-flop has its set terminal connected to the output of the comparator and its reset terminal connected to a clock signal. A counter, connected to the Q terminal of the RS flip-flop, is used to downsample and count the output of the Q terminal of the RS flip-flop and then output the count. The charge pump switch is controlled by the Q output of the RS flip-flop; the temperature current generation module's I... PTAT A base compensation resistor is provided in the current branch to eliminate the nonlinear error caused by the finite current gain of the bipolar transistor.

2. The calibration-free high-precision temperature sensor according to claim 1, characterized in that, The I CTAT Current branch and I PTAT The current branches are connected in parallel, and the I PTAT The base of the bipolar transistor Q2 in the current branch is connected to the base compensation resistor R. βb Grounding.

3. The calibration-free high-precision temperature sensor according to claim 2, characterized in that, The temperature current generation module includes: a MOSFET M P1 MOSFET M P2 MOSFET M P3 MOSFET M P4 MOSFET M N1 Resistors R1, R2, and base compensation resistor R βb Bipolar transistor Q1, bipolar transistor Q2, bipolar transistor Q3, charge pump switch SW1, comparator A1 and comparator A2; Among them, the MOS transistor M P1 The MOS transistor M P2 The MOS transistor M P3 and the MOS transistor M P4 The sources of all are connected to the power supply terminal, and the MOS transistor M P1 The MOS transistor M P2 The MOS transistor M P3 The gate of the MOSFET is connected to the output of the comparator A1; the MOSFET M P1 The drain of the resistor is connected to the first terminal of the resistor R1 and the non-inverting input terminal of the comparator A1, respectively. The inverting input terminal of the comparator A1 is connected to the MOS transistor M. P2 The drain of the MOSFET and the emitter of the bipolar transistor Q2; the MOS transistor M P3 The drains of the transistors are connected to the emitter of the bipolar transistor Q3 and the non-inverting input of the comparator A2, respectively. The second end of resistor R1 is connected to the emitter of bipolar transistor Q1, and both the base and collector of bipolar transistor Q1 are grounded; the base of bipolar transistor Q2 is connected to the base compensation resistor R. βb The first terminal is the collector of the bipolar transistor Q2 and the base compensation resistor R. βb The second terminal of each is grounded, and the base compensation resistor R βb A charge pump switch SW1 is connected above it; The base and collector of the bipolar transistor Q3 are both grounded; the MOS transistor M N1 The base of the resistor is connected to the output of the comparator A2, and the source is connected to the inverting input of the comparator A2 and the first end of the resistor R2, respectively. The second end of the resistor R2 is grounded. The MOS transistor M P4 Drain output Current, the MOS transistor M N1 Drain output Electric current.

4. The calibration-free high-precision temperature sensor according to claim 1, characterized in that, The Current and with the Current ratio The expression is: ； in, The current ratio is... It is a constant and independent of temperature.

5. The calibration-free high-precision temperature sensor according to claim 3, characterized in that, The base compensation resistor R βb The expression for the resistance value is: ； in, The base compensation resistor R βb The resistance value; The voltage difference between the base and emitter of the bipolar transistor Q1 and the bipolar transistor Q2; This is the base-emitter voltage of the bipolar transistor Q3; Boltzmann's constant; Thermodynamic temperature; The charge of an electron; This is the transistor saturation current; It is a natural constant.

6. The calibration-free high-precision temperature sensor according to claim 1, characterized in that, The expression for the output value of the counter is: ； in, for The discharge time of the current; for Charging time of the current.

7. The calibration-free high-precision temperature sensor according to claim 1, characterized in that, The average charge of the integrating capacitor is 0 over multiple time periods.

8. The calibration-free high-precision temperature sensor according to claim 1, characterized in that, The charge pump switch is output from the Q terminal of the RS flip-flop. Control, when the Q output of the RS flip-flop... When it is high, the The current charges the integrating capacitor; when the Q output of the RS flip-flop... When it is low, the The current discharges the integrating capacitor.

Images