Temperature measurement chip circuit compatible with platinum thermal resistor, NTC and digital semiconductor temperature measurement

Abstract

The invention discloses a temperature measurement chip circuit compatible with platinum thermal resistance, NTC and digital semiconductor temperature measurement. According to the circuit, three temperature measurement principles are fused, a single-chip implementation scheme of temperature measurement and acquisition of PT100 / PT1000 / NTC thermistors outside a multi-channel chip and temperature measurement of PN nodes inside the chip is fused, and a time division multiplexing mode is adopted, so that the measurement matching performance among channels is improved, and the power consumption is reduced. During calibration, the internal PN node array temperature measurement channel is calibrated firstly, error correction is performed on the analog front-end circuit, and then the external temperature measurement channel is calibrated by using the precision of the PN node array, so that the calibration efficiency is improved. Reasonable reference voltage is adopted for different internal and external temperature measurement circuits, and for an external temperature measurement channel, differential voltage between two pins is selected, so that the influence caused by driving current deviation is counteracted in calculation. For an internal PN node temperature measurement channel, an internal low-temperature-drift reference voltage VREF is selected, and the influence caused by the reference voltage deviation is counteracted from calculation.

Description

Technical Field

[0001] The invention relates to a temperature measurement chip circuit compatible with platinum thermal resistance, NTC and digital semiconductor temperature measurement. Background Art

[0002] A temperature sensor is a device for monitoring temperature, generally composed of a temperature-sensitive element (such as a thermistor, thermocouple, etc.) and a circuit; the temperature-sensitive element senses changes in the temperature to be monitored and converts it into a thermoelectric potential or resistance change. The element is connected to the circuit, and the circuit outputs a voltage or current.

[0003] The temperature sensitive element can be a thermocouple, which is generally made of metal wire and generates thermoelectric potential after sensing the temperature. Thermocouples can also be connected in series to form a thermopile, which can amplify the thermoelectric potential generated by the thermocouple and improve the accuracy of the temperature sensor.

[0004] Due to the particularity of thermocouples, the manufactured metal wire is generally very fragile. When the sensor is in a very harsh environment, vibration, impact, etc. are a great test to the reliability of the sensor; especially when thermocouples are connected in series to form a thermopile, if any thermocouple in the series connection is broken, it means that the thermopile is broken, and the temperature sensor loses the ability to monitor temperature. Therefore, it is urgent to develop a high-reliability temperature sensor. Summary of the invention

[0005] The purpose of the present invention is to provide a temperature measurement chip circuit compatible with platinum thermal resistors, NTC and digital semiconductor temperature measurement in order to solve the above problems. The chip circuit integrates three temperature measurement principles, and integrates the multi-channel PT100 / PT1000 / NTC and the PN node temperature array for temperature measurement in the chip, so that the resolution accuracy of the temperature measurement in the chip reaches 1mK.

[0006] The circuit of the present invention comprises a PN junction array module, a temperature sensing circuit module, a driving current source and a switching switch module, a temperature measurement signal selection and amplification module, a clock module, a reference voltage module, an analog-to-digital converter module, a filter and a microprocessor module, a digital control module, a storage module, an I2C and single bus communication interface module, a power management module and a fault diagnosis module.

[0007] Furthermore, in the PN junction array module, the silicon-based chip temperature sensor uses the base-emitter voltage V BE Temperature characteristics, when V BE When the voltage is greater than the threshold voltage of the transistor, the voltage-current characteristic equation of the transistor is:

[0008]

[0009] Among them, I c is the collector current, I sis the reverse saturation current of the transistor, q is the charge on the electron, k is the Boltzmann constant, T is the absolute temperature in Kelvin; V BE The temperature-voltage characteristic equation is:

[0010]

[0011] Among them, V BE The voltage has a linear characteristic with a negative temperature coefficient. In the latest P-substrate N-well CMOS process, PNP transistors are used to form a PN junction.

[0012] Furthermore, the temperature sensing circuit module adopts a dual-channel triode proportional differential temperature measurement circuit to convert the voltage V output by the PN junction array module into BE Convert it into a voltage signal that can be collected by an analog-to-digital converter ADC;

[0013] Specifically: Two high-precision current sources I c1 ,I c2 They drive two PNP transistors with the same number of n, and the corresponding voltages are V BE1 and V BE2 , forming a differential temperature measurement unit, and the following relationship is obtained:

[0014]

[0015] Where T and ΔV BE =V BE1 -V BE2 It is a completely linear relationship. The other parameters in the formula They are fixed values ​​and do not change with the change of temperature. BE It has a positive temperature coefficient characteristic and a linearity of up to 0.05%.

[0016] Furthermore, the driving current source and switching switch module are used to drive the external PT100 / PT1000 / NTC temperature measuring device, and have the characteristics of high precision and high impedance; 10 external PT100 / PT1000 / NTC temperature measurement channels share the same set of driving current sources and the driving current source of the switching switch module, which is realized by time division multiplexing of the driving current source and the CMOS transmission gate switches 1 to 10 of the switching switch module; the driving current source and the switching switch module integrate a pair of complementary NMOS and PMOS transistors to form a transmission gate switch; the switching logic of the transmission gate is controlled by complementary EN and ENB signals, which are switched and controlled by the digital finite state machine FSM of the digital control module, and can arbitrarily configure and select the channel number to be turned on.

[0017] Furthermore, the temperature measurement signal selection and amplification module selects 1 out of 11 between the 10 measurement channels of the off-chip PT100 / PT1000 / NTC and the 1 measurement channel of the on-chip PN junction array module; at the same time, the selected differential voltage is amplified through the gain variable amplifier PGA, fully utilizing the dynamic range of the analog-to-digital converter ADC and improving the temperature resolution.

[0018] Further, the reference voltage module provides a reference voltage for quantizing the input signal for the analog-to-digital converter ADC; the reference voltage is provided by an internal low-temperature drift bandgap reference voltage, or provided by a reference resistor end of an external PT100 / PT1000 / thermistor measurement channel; for the external PT100 / PT1000 / thermistor measurement channel, the differential voltage between the REFINP pin and the REFINM pin is selected to offset the drive current I BIAS The impact of the deviation, the output signal percentage of the analog-to-digital converter ADC is:

[0019]

[0020] The ADC output is only related to the measured resistance R T With external reference resistor R REF Gain is the programmable gain of PGA; V REFINP Represents the voltage on the REFINP pin, V REFINM Represents the voltage on the REFINM pin, V VINM Represents the voltage on the VINM pin, R REF is a high-precision low-temperature drift resistor, so the above formula can meet the requirements of high-precision temperature measurement; for the internal transistor temperature measurement channel, the low-temperature drift reference voltage V generated by the internal bandgap reference circuit is selected REF ,Calculated to offset the influence of reference voltage deviation, the output signal percentage of ADC is:

[0021]

[0022] The ADC output is only related to V BE With ΔV BE It is related to the ratio of , α is a fixed proportional coefficient, Gain is the programmable gain of PGA, and the PN node array has a high degree of mutual matching, so the above formula can meet the requirements of high-precision temperature measurement.

[0023] Furthermore, the filter and microprocessor module perform down-sampling filtering, low-pass filtering, and a notch filter to resist 50 / 60Hz power frequency interference on the output signal of the analog-to-digital converter module. The output data of the filter enters the microprocessor unit for advanced calibration and compensation processing to output an accurate temperature value. Due to the nonlinear characteristics of the temperature-voltage characteristic curves of PT100 / PT1000 / NTC and BJT, the circuit supports the third-order calibration fitting operation of the temperature value, and the calculation formula is expressed as:

[0024] T DATA =a*(T RAW -T 0 ) 3 +b*(T RAW -T 0 ) 2 +c*(T RAW -T 0 )+d Formula 6

[0025] Among them, T DATA represents the temperature value after third-order calibration fitting, T RAW Indicates the temperature value before calibration, T 0 It represents the reference temperature value, a is the third-order coefficient, b is the second-order coefficient, c is the first-order coefficient, and d is the zero-point coefficient; each channel corresponds to its own unique high-order compensation coefficient, which is stored in the non-volatile memory of the storage module.

[0026] Furthermore, the clock module integrates an on-chip low-temperature drift oscillator and a frequency regulator, can provide an accurate clock for the system, and has a frequency calibration function; the analog-to-digital converter module uses a Sigma-Delta ADC; the digital control unit uses an internal finite state machine FSM to logically control the PN junction array module, the temperature sensor circuit module, the drive current source and switching switch module, the temperature measurement signal selection and amplification module, the clock module, the reference voltage module, the analog-to-digital converter module, the filter and microprocessor module, the digital control module, the storage module, the I2C and single bus communication interface module; the storage module, wherein the non-volatile memory that is repeatedly erased and written is used to store the transmission signal. The key information of each channel of the sensor, the register is used to read and write external data, and also includes a multi-byte first-in-first-out unit to provide sufficient data cache during high-speed temperature measurement conversion; the I2C and single bus communication interface module, its communication mode includes two major categories of I2C and single bus; the power management module includes a voltage protection unit, which effectively protects the circuit from damage during overvoltage and reverse connection; includes two regulators to divide the internal power supply into analog power supply and digital power supply; includes a power-on reset circuit unit digital part to provide a reset signal; the fault diagnosis unit is equipped with multiple comparators for automatically detecting whether the internal power supply voltage, signal chain voltage, clock frequency, and communication status of the circuit are within the set value range.

[0027] Furthermore, the circuit operation of the present invention is implemented as follows:

[0028] The current source and switch of the driving current source and switching switch module respectively drive the 10 PT100 / PT1000 / NTC channels with current, and the PN junction array module and the temperature sensor circuit module will generate the temperature voltage signal generated by the PN junction. The 11 input signals are selected by the temperature measurement signal selection and amplification module, and then amplified by the gain variable amplifier PGA, and then sent to the analog-to-digital converter ADC of the analog-to-digital converter module for data conversion. The output digital signal is calibrated by the digital filter and microcontroller of the filter and microprocessor module to obtain the temperature data; the temperature data is stored in the register of the storage module through the finite state machine control of the digital control module; the user accesses the register through the I2C or single bus communication mode of the I2C and single bus communication interface module to read and obtain these temperature values;

[0029] When performing temperature calibration, select high-precision constant temperature equipment as the calibration environment, first calibrate the internal transistor temperature measurement channel, correct the measurement error caused by the analog front-end circuit composed of the temperature measurement signal selection and amplification module, clock module, reference voltage module, and analog-to-digital converter module, and store the correction parameters in the non-volatile memory of the storage module; after the internal temperature measurement channel is calibrated, calibrate the 10 external PT100 / PT1000 / NTC temperature measurement channels; since the external 10 temperature measurement channels and the internal temperature measurement channels share the same set of analog front-end circuits, the external chip is based on thermistors. The acquisition errors caused by the principle devices and the driving current source and switching switch module can be compared with the acquisition errors caused by the semiconductor type of the PN junction array module and the temperature sensor circuit module inside the chip, and the difference between the two acquisition errors is stored in the digital register for compensation: at ultra-high temperatures greater than 150 degrees, PT100 / PT1000 can exert the best characteristic advantages of temperature resistance change, and at ultra-low temperatures less than -90 degrees, NTC resistors can exert the best characteristic advantages of temperature resistance change, and in the range of -90 to 150 degrees, the semiconductor digital circuits inside the chip can exert the best characteristics.

[0030] The beneficial effects of the present invention are as follows:

[0031] The present invention integrates the temperature measurement and collection of multi-channel external PT100 / PT1000 / NTC thermistors and the temperature measurement of the internal PN node of the chip into a single chip, and improves the measurement matching between the channels and saves power consumption by adopting the form of time division multiplexing.

[0032] During calibration, the present invention first calibrates the internal PN node array temperature measurement channel, performs error correction on the analog front end (AFE) circuit, and then uses the accuracy of the PN node array to calibrate the external PT100 / PT1000 / NTC temperature measurement channel, thereby improving calibration efficiency.

[0033] The internal driving current source of the present invention sequentially selects 10 external PT100 / PT1000 / NTC temperature measurement channels through a high-speed transmission gate switch combined with a digital logic circuit. The transmission gate switch has a fast switching speed, and the switch logic is controlled by an internal finite digital state machine, and the channel number that needs to be opened can be arbitrarily selected and configured.

[0034] The present invention adopts reasonable reference voltage for different internal and external temperature measurement circuits: for the external PT100 / PT1000 / NTC temperature measurement channel, the differential voltage between the REFINP and REFINM pins is selected to offset the influence of the driving current deviation in calculation. For the internal PN node temperature measurement channel, the low temperature drift reference voltage VREF generated by the internal bandgap reference circuit is selected to offset the influence of the reference voltage deviation in calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is the overall framework diagram of the present invention.

[0036] Figure 2 This is a cross-sectional view of a PNP transistor.

[0037] Figure 3 It is a PNP transistor differential temperature measurement unit.

[0038] Figure 4 It is a CMOS transmission gate structure. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0040] The present invention provides a temperature measurement chip circuit that is compatible with platinum resistance thermometers, NTC and digital semiconductor temperature measurement, and a single-chip system-on-chip (System-On-Chip, SOC) temperature sensor that integrates three temperature measurement principles. The present invention simultaneously integrates the acquisition of multi-channel (10 channels in this implementation case) PT100 / PT1000 / NTC, and the PN node temperature array for on-chip temperature measurement. The acquisition system can achieve the integration of different temperature measurement principles in the smallest single-chip volume, and can collect PT100 / PT1000 in the high temperature range of 800°C from different remote locations, as well as low-cost NTC temperature measurement nodes, and can also compare and collect digital semiconductor temperatures inside the chip. The resolution accuracy of on-chip temperature measurement reaches 1mK,

[0041] like Figure 1 As shown, the present invention includes a PN junction array module, a temperature sensing circuit module, a driving current source and switching switch module, a temperature measurement signal selection and amplification module, a clock module, a reference voltage module, an analog-to-digital converter module, a filter and a microprocessor module, a digital control module, a storage module, an I2C and single bus communication interface module, a power management module and a fault diagnosis module.

[0042] like Figure 1As shown, the present invention can simultaneously support 10 external PT100 / PT1000 / / NTC temperature measurement channels and 1 internal BJT temperature measurement channel. PT100 / PT1000 can adopt a 4-wire system, and the internal temperature measurement is realized by using the PN junction temperature characteristics of BJT. The 10 external temperature-sensitive resistor (PT100 / PT1000 / NTC) temperature measurement channels and the 1 internal BJT temperature measurement channel adopt the form of time division multiplexing, which saves power consumption to the greatest extent and improves the measurement matching between channels. The signal is selected by MUX, and is given to ADC for data conversion through a gain variable amplifier (PGA) and a buffer (BUF). The output digital signal is then processed by a digital filter and a microcontroller unit (MCU) calibration algorithm to obtain temperature data and store it in the register of the corresponding channel. The user end can access the register through I2C or single bus (OWI) communication to read and obtain these temperature values. The chip also has an EEPROM that can be erased and written multiple times to save the calibration parameters of each temperature measurement channel.

[0043] For 10 external temperature measurement channels, when calibrating in the same high-precision temperature environment, the calibration reading of the previous channel can be used as the standard control group for the next channel. For example, after channel 1 completes high-order calibration, its output accuracy reaches the expected standard and can be used as the comparison channel for channel 2 calibration, and so on. In this way, as the number of channels increases, there will be more standard sources for comparison, reducing the impact of fluctuation errors of a single calibration source.

[0044] The PN junction array module has a high linearity temperature-voltage characteristic of the PN junction voltage of the bipolar junction transistor (BJT), which is used to sense temperature information. The silicon-based chip temperature sensor uses the base-emitter voltage V BE Temperature characteristics. When V BE When the voltage is greater than the threshold voltage of the transistor, the voltage-current characteristic equation of the transistor is:

[0045]

[0046] Among them, I c is the collector current, I s is the reverse saturation current of the transistor, q is the charge on the electron (1.602×10–19 Coulomb), k is the Boltzmann constant (1.38×10–23), and T is the absolute temperature in Kelvin. Therefore, V BE The temperature-voltage characteristic equation is:

[0047]

[0048] Among them, V BEThe voltage has a linear characteristic with a negative temperature coefficient. In the latest P-substrate N-well CMOS process, a PNP transistor is used to form a PN junction. The cross-sectional structure is as follows: Figure 2 shown.

[0049] The temperature sensing circuit module adopts a dual-channel triode proportional differential temperature measurement circuit to convert the voltage V output by the PN junction array module into BE Converted into a voltage signal that can be collected by an analog-to-digital converter (ADC), the structure is as follows Figure 3 shown.

[0050] Among them, two high-precision current sources I c1 ,I c2 They drive two PNP transistors with the same number of n, and the corresponding voltages are V BE1 and V BE2 , forming a differential temperature measurement unit, and the following relationship is obtained:

[0051]

[0052] It can be seen that T and ΔV BE =V BE1 -V BE2 It is a completely linear relationship. The other parameters in the formula are fixed values ​​and do not change with temperature. BE Positive temperature coefficient characteristic, linearity up to 0.05%, by measuring ΔV BE The value of ΔV can be used to calculate the accurate temperature value, which is the basic theoretical basis for CMOS process temperature measurement. BE In addition to high temperature linearity, it also has the characteristics of low noise.

[0053] The driving current source and switching switch module are used to drive external PT100 / PT1000 / NTC and other temperature measuring devices, and have the characteristics of high precision and high impedance. The 10 external PT100 / PT1000 / NTC temperature measurement channels share the same set of driving current sources and the driving current source of the switching switch module, which is realized by time division multiplexing of the driving current source and the CMOS transmission gate switches 1 to 10 of the switching switch module. The driving current source and the switching switch module integrate a pair of complementary NMOS and PMOS transistors to form a transmission gate switch, and the structure is as follows: Figure 2-3CMOS transmission gates switch quickly, and the switching time of high-speed transmission gates is usually less than 1us. At the same time, the on-resistance of the transmission gate switch is relatively constant and does not change with the VDD voltage. The switching logic of the transmission gate is controlled by the complementary EN and ENB signals, which are switched by the digital finite state machine (FSM) of the digital control module, and can arbitrarily configure the channel number to be turned on.

[0054] The temperature measurement signal selection and amplification module selects 1 out of 11 between 10 measurement channels of the off-chip PT100 / PT1000 / NTC and 1 measurement channel of the on-chip PN junction array module; at the same time, the selected differential voltage is amplified through a programmable-gain-amplifier (PGA), making full use of the dynamic range of the analog-to-digital converter (ADC) and improving the temperature resolution.

[0055] The clock module integrates an on-chip low-temperature drift oscillator and a frequency regulator, can provide an accurate clock for the system, and has a frequency calibration function.

[0056] The reference voltage module provides a reference voltage for the analog-to-digital converter (ADC) to quantize the input signal. It is provided by the internal low-temperature drift bandgap reference voltage or by the reference resistor end of the external PT100 / PT1000 / thermistor measurement channel. For the external PT100 / PT1000 / thermistor measurement channel, Figure 1 The connection mode is to select the differential voltage between the REFINP pin and the REFINM pin to offset the drive current I BIAS The impact of the deviation, the output signal percentage of the analog-to-digital converter ADC is:

[0057]

[0058] The ADC output is only related to the measured resistance R T With external reference resistor R REF Gain is the programmable gain of PGA. REFINP Represents the voltage on the REFINP pin, V REFINM Represents the voltage on the REFINM pin, represents the voltage on the VINP pin, V VINM Represents the voltage on the VINM pin, R REF For the internal transistor temperature measurement channel, the low temperature drift reference voltage V generated by the internal bandgap reference circuit is selected. REF ,Calculated to offset the influence of reference voltage deviation, the output signal percentage of ADC is:

[0059]

[0060] The ADC output is only related to V BE With ΔV BE α is a fixed proportional coefficient, and Gain is the programmable gain of PGA. PN node arrays have a high degree of mutual matching, so the above formula can meet the requirements of high-precision temperature measurement.

[0061] The analog-to-digital converter module uses Sigma-Delta ADC (Σ-ΔADC), which is a high-precision analog-to-digital converter with the main advantages of high resolution and excellent noise suppression. Σ-ΔADC uses oversampling and noise shaping technology to move the quantization noise in the analog-to-digital conversion process to a higher frequency, thereby significantly improving the conversion accuracy and resolution. Its basic principle is to use a Δ-Σ modulator to convert the input signal into a high-frequency bit stream, and then restore the signal to the required digital value through a digital extraction filter.

[0062] The filter and microprocessor module described above. The output signal of the analog-to-digital converter module is subjected to downsampling filtering, low-pass filtering, and a notch filter to resist 50 / 60Hz power frequency interference. The output data of the filter enters the microcontroller unit (MCU) for advanced calibration and compensation processing to output an accurate temperature value. Due to the nonlinear characteristics of the temperature-voltage characteristic curves of PT100 / PT1000 / NTC and BJT, it is difficult for traditional first-order and second-order fitting to achieve an accuracy level of 1mK. The circuit of the present invention supports third-order calibration fitting operations for temperature values, and the calculation formula can be expressed as:

[0063] T DATA =α*(T RAW -T 0 ) 3 +b*(T RAW -T 0 ) 2 +c*(T RAW -T 0 )+d Formula 6

[0064] Among them, T DATA represents the temperature value after third-order calibration fitting, T RAW Indicates the temperature value before calibration, T 0 represents the reference temperature value, a is the third-order coefficient, b is the second-order coefficient, c is the first-order coefficient, and d is the zero-point coefficient. Each channel corresponds to its own unique high-order compensation coefficient, which is stored in the non-volatile memory of module 10.

[0065] The digital control unit performs logic control on the PN junction array module, temperature sensor circuit module, drive current source and switch module, temperature measurement signal selection and amplification module, clock module, reference voltage module, analog-to-digital converter module, filter and microprocessor module, digital control module, storage module, I2C and single bus communication interface module of the chip circuit of the present invention through an internal finite state machine (FSM), thereby realizing functions such as measurement, calculation and communication.

[0066] The storage unit includes a non-volatile memory that can be erased and written multiple times and is used to store key information such as calibration parameters of each channel of the sensor. The register is used to read and write external data. It also includes a multi-byte first-in-first-out unit (FIFO) to provide sufficient data cache during high-speed temperature measurement conversion.

[0067] The I2C and single bus communication interface module has two communication modes: I2C and single bus. In order to improve reliability, it also has a communication verification unit for verifying data transmission.

[0068] The power management module and the voltage protection unit effectively protect the circuit of the present invention from being damaged in the event of overvoltage and reverse connection; the two voltage regulators (AVDD and DVDD) divide the internal power supply into an analog power supply (AVDD) and a digital power supply (DVDD), thereby reducing mutual interference between the analog unit and the digital unit; the power-on reset circuit unit (Power-On-Reset, POR) provides a reset signal for the digital part, thereby ensuring that the circuit starts working from a certain state after power-on.

[0069] The fault diagnosis unit is provided with multiple comparators for automatically detecting whether the power supply voltage, signal chain voltage, clock frequency, communication status, etc. inside the circuit of the present invention are within a normal value range.

[0070] The specific working process of the circuit of the present invention is as follows:

[0071] For external thermistor measurement channels, follow Figure 1The connection mode is adopted, and the current source and switch of the driving current source and the switching switch module respectively drive the 10 PT100 / PT1000 / NTC channels with current. The PN junction array module and the temperature sensor circuit module will generate the temperature voltage signal generated by the PN junction. The 11 input signals are amplified by the channel selection (Multiplexer, MUX) of the temperature measurement signal selection and amplification module after passing through the gain variable amplifier (PGA), and then sent to the analog-to-digital converter (ADC) of the analog-to-digital converter module for data conversion. The output digital signal passes through the digital filter and microcontroller module of the filter and microprocessor module for high-order calibration operation to obtain temperature data; the temperature data is stored in the register of the storage module through the finite state machine control of the digital control module. Users can access the register through the I2C or single bus (OWI) communication mode of the I2C and single bus communication interface module to read and obtain these temperature values.

[0072] When performing temperature calibration, select high-precision constant temperature equipment (including but not limited to constant temperature bath) as the calibration environment, first calibrate the internal transistor (BJT) temperature measurement channel, correct the measurement error generated by the analog front end (Analog-Front-End, AFE) circuit composed of the temperature measurement signal selection and amplification module, clock module, reference voltage module, and analog-to-digital converter module, and store the correction parameters in the non-volatile memory (NVM) of the storage module. After the internal temperature measurement channel is calibrated, calibrate the 10 external PT100 / PT1000 / NTC temperature measurement channels. Since the 10 external temperature measurement channels and the internal temperature measurement channels share the same analog front-end (AFE) circuit, the acquisition errors caused by the thermistor-based devices outside the chip, as well as the driving current source and switching switch modules, can be compared with the acquisition errors caused by the semiconductor type of the PN junction array module and temperature sensor circuit module inside the chip. The difference between the two acquisition errors is stored in a digital register for compensation: at ultra-high temperatures greater than 150 degrees, PT100 / PT1000 can exert the best characteristic advantages of temperature resistance change, and at ultra-low temperatures less than -90 degrees, NTC resistors can exert the best characteristic advantages of temperature resistance change. In the range of -90 to 150 degrees, the semiconductor digital circuits inside the chip can exert the best characteristics.

Claims

1. Compatible with platinum thermal resistance, NTC and digital semiconductor temperature measurement temperature measurement chip circuit, characterized by The chip circuit integrates three temperature measurement principles, including multi-channel PT100 / PT1000 / NTC and the PN junction temperature array for on-chip temperature measurement, so that the resolution accuracy of on-chip temperature measurement reaches 1mK.

2. The temperature measurement chip circuit compatible with platinum thermal resistance, NTC and digital semiconductor temperature measurement according to claim 1 is characterized in that The circuit includes a PN junction array module, a temperature sensing circuit module, a driving current source and switching switch module, a temperature measurement signal selection and amplification module, a clock module, a reference voltage module, an analog-to-digital converter module, a filter and a microprocessor module, a digital control module, a storage module, an I2C and single bus communication interface module, a power management module and a fault diagnosis module.

3. The temperature measurement chip circuit compatible with platinum thermal resistance, NTC and digital semiconductor temperature measurement according to claim 2 is characterized in that The PN junction array module, wherein the silicon-based chip temperature sensor utilizes the base-emitter voltage V BE Temperature characteristics, when V BE When the voltage is greater than the threshold voltage of the transistor, the voltage-current characteristic equation of the transistor is: Among them, I c is the collector current, I s is the reverse saturation current of the transistor, q is the charge on the electron, k is the Boltzmann constant, T is the absolute temperature in Kelvin; V BE The temperature-voltage characteristic equation is: Among them, V BE The voltage has a linear characteristic with a negative temperature coefficient. In the latest P-substrate N-well CMOS process, PNP transistors are used to form a PN junction.

4. The temperature measurement chip circuit compatible with platinum thermal resistance, NTC and digital semiconductor temperature measurement according to claim 2 is characterized in that The temperature sensing circuit module adopts a dual-channel triode proportional differential temperature measurement circuit to convert the voltage V output by the PN junction array module into BE Convert it into a voltage signal that can be collected by an analog-to-digital converter ADC; Specifically: Two high-precision current sources I c1 ,I c2 They drive two PNP transistors with the same number of n, and the corresponding voltages are V BE1 and V BE2 , forming a differential temperature measurement unit, and the following relationship is obtained: Where, T and ΔV BE =V BE1 -V BE2 It is a completely linear relationship. The other parameters n, k, q, They are fixed values ​​and do not change with the change of temperature. BE It has a positive temperature coefficient characteristic and a linearity of up to 0.05%.

5. The temperature measurement chip circuit compatible with platinum thermal resistance, NTC and digital semiconductor temperature measurement according to claim 4 is characterized in that The driving current source and switching switch module are used to drive the external PT100 / PT1000 / NTC temperature measuring device, and have the characteristics of high precision and high impedance; The 10 external PT100 / PT1000 / NTC temperature measurement channels share the same set of driving current sources and the driving current sources of the switching switch module, which is realized by time-division multiplexing of the driving current sources and the CMOS transmission gate switches 1 to 10 of the switching switch module; the driving current sources and the switching switch module integrate a pair of complementary NMOS and PMOS transistors to form a transmission gate switch; the switching logic of the transmission gate is controlled by complementary EN and ENB signals, which are switched and controlled by the digital finite state machine FSM of the digital control module, and can arbitrarily configure and select the channel number to be turned on.

6. The temperature measurement chip circuit compatible with platinum thermal resistance, NTC and digital semiconductor temperature measurement according to claim 4, characterized in that The temperature measurement signal selection and amplification module selects 1 out of 11 between 10 measurement channels of the off-chip PT100 / PT1000 / NTC and 1 measurement channel of the on-chip PN junction array module; at the same time, the selected differential voltage is amplified through a gain variable amplifier PGA, fully utilizing the dynamic range of the analog-to-digital converter ADC and improving the temperature resolution.

7. The temperature measurement chip circuit compatible with platinum thermal resistance, NTC and digital semiconductor temperature measurement according to claim 4, characterized in that The reference voltage module provides a reference voltage for quantizing the input signal for the analog-to-digital converter ADC; the reference voltage is provided by an internal low-temperature drift bandgap reference voltage, or by a reference resistor end of an external PT100 / PT1000 / thermistor measurement channel; for the external PT100 / PT1000 / thermistor measurement channel, the differential voltage between the REFINP pin and the REFINM pin is selected to offset the drive current I BIAS The impact of the deviation, the output signal percentage of the analog-to-digital converter ADC is: The ADC output is only related to the measured resistance R T With external reference resistor R REF Gain is the programmable gain of PGA; V REFINP Represents the voltage on the REFINP pin, V REFINM Represents the voltage on the REFINM pin, V VINM Represents the voltage on the VINM pin, R REF is a high-precision low-temperature drift resistor, so the above formula can meet the requirements of high-precision temperature measurement; for the internal transistor temperature measurement channel, the low-temperature drift reference voltage V generated by the internal bandgap reference circuit is selected REF ,Calculated to offset the influence of reference voltage deviation, the output signal percentage of ADC is: The ADC output is only related to V BE With ΔV BE It is related to the ratio of , α is a fixed proportional coefficient, Gain is the programmable gain of PGA, and the PN node array has a high degree of mutual matching, so the above formula can meet the requirements of high-precision temperature measurement.

8. The temperature measurement chip circuit compatible with platinum thermal resistance, NTC and digital semiconductor temperature measurement according to claim 4, characterized in that The filter and microprocessor module perform down-sampling filtering, low-pass filtering and notch filtering to resist 50 / 60Hz power frequency interference on the output signal of the analog-to-digital converter module. The output data of the filter enters the microprocessor unit for advanced calibration and compensation processing to output an accurate temperature value. Due to the nonlinear characteristics of the temperature-voltage characteristic curves of PT100 / PT1000 / NTC and BJT, the circuit supports the third-order calibration fitting operation of the temperature value, and the calculation formula is expressed as: T DATA = a * (T RAW - T0) 3 + b * (T RAW - T0) 2 + c * (T RAW - T0) + d Equation 6 Among them, T DATA represents the temperature value after third-order calibration fitting, T RAW It represents the temperature value before calibration, T0 represents the reference temperature value, a represents the third-order coefficient, b represents the second-order coefficient, c represents the first-order coefficient, and d represents the zero-point coefficient. Each channel corresponds to its own unique high-order compensation coefficient, which is stored in the non-volatile memory of the storage module.

9. The temperature measurement chip circuit compatible with platinum thermal resistance, NTC and digital semiconductor temperature measurement according to claim 4, characterized in that The clock module integrates an on-chip low-temperature drift oscillator and a frequency regulator, can provide an accurate clock for the system, and has a frequency calibration function; the analog-to-digital converter module uses a Sigma-Delta ADC; the digital control unit performs logical control on the PN junction array module, the temperature sensor circuit module, the drive current source and the switching switch module, the temperature measurement signal selection and amplification module, the clock module, the reference voltage module, the analog-to-digital converter module, the filter and the microprocessor module, the digital control module, the storage module, the I2C and the single bus communication interface module through an internal finite state machine FSM; the storage module, wherein the non-volatile memory that can be repeatedly erased and written is used to store the key information of each channel of the sensor, the register is used to read and write external data, and also includes a multi-byte first-in-first-out unit to provide enough data cache during high-speed temperature measurement conversion; the I2C and single bus communication interface module, its communication mode includes two categories of I2C and single bus; the power management module includes a voltage protection unit, which effectively protects the circuit from being damaged in the event of overvoltage and reverse connection; it includes two voltage regulators to divide the internal power supply into an analog power supply and a digital power supply; The digital part of the power-on reset circuit unit provides a reset signal; the fault diagnosis unit is provided with multiple comparators for automatically detecting whether the power supply voltage, signal chain voltage, clock frequency and communication status inside the circuit are within the set value range.

10. The temperature measurement chip circuit compatible with platinum thermal resistance, NTC and digital semiconductor temperature measurement according to claim 4, characterized in that: The circuit works as follows: The current source and switch of the driving current source and switching switch module respectively drive the 10 PT100 / PT1000 / NTC channels with current, and the PN junction array module and the temperature sensor circuit module will generate the temperature voltage signal generated by the PN junction. The 11 input signals are selected by the temperature measurement signal selection and amplification module, and then amplified by the gain variable amplifier PGA, and then sent to the analog-to-digital converter ADC of the analog-to-digital converter module for data conversion. The output digital signal is calibrated by the digital filter and microcontroller of the filter and microprocessor module to obtain the temperature data; the temperature data is stored in the register of the storage module through the finite state machine control of the digital control module; the user accesses the register through the I2C or single bus communication mode of the I2C and single bus communication interface module to read and obtain these temperature values; When performing temperature calibration, a high-precision constant temperature device is selected as the calibration environment, and the internal transistor temperature measurement channel is calibrated first, and the measurement error generated by the analog front-end circuit composed of the temperature measurement signal selection and amplification module, the clock module, the reference voltage module, and the analog-to-digital converter module is corrected, and the correction parameters are stored in the non-volatile memory of the storage module; After the internal temperature measurement channel is calibrated, the 10 external PT100 / PT1000 / NTC temperature measurement channels are calibrated; since the 10 external temperature measurement channels and the internal temperature measurement channels share the same set of analog front-end circuits, the acquisition errors caused by the thermistor-based devices outside the chip and the driving current source and switching switch modules and the acquisition errors caused by the semiconductor type of the PN junction array module and temperature sensor circuit module inside the chip can be compared, and the difference between the two acquisition errors is stored in the digital register for compensation: at ultra-high temperatures greater than 150 degrees, PT100 / PT1000 can play the best characteristic advantage of temperature resistance change, and at ultra-low temperatures less than -90 degrees, NTC resistors can play the best characteristic advantage of temperature resistance change, and in the range of -90 to 150 degrees, the semiconductor digital circuits inside the chip can play the best characteristics.

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