CN115452177A - Temperature sensor circuit - Google Patents

Temperature sensor circuit Download PDF

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Publication number
CN115452177A
CN115452177A CN202211069692.6A CN202211069692A CN115452177A CN 115452177 A CN115452177 A CN 115452177A CN 202211069692 A CN202211069692 A CN 202211069692A CN 115452177 A CN115452177 A CN 115452177A
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China
Prior art keywords
sigma
phi
digital converter
voltage
delta analog
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CN202211069692.6A
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Chinese (zh)
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吕宏鸣
周志宁
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ShanghaiTech University
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ShanghaiTech University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M3/00—Conversion of analogue values to or from differential modulation
    • H03M3/30—Delta-sigma modulation
    • H03M3/322—Continuously compensating for, or preventing, undesired influence of physical parameters
    • H03M3/352—Continuously compensating for, or preventing, undesired influence of physical parameters of deviations from the desired transfer characteristic
    • H03M3/354—Continuously compensating for, or preventing, undesired influence of physical parameters of deviations from the desired transfer characteristic at one point, i.e. by adjusting a single reference value, e.g. bias or gain error
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M3/00—Conversion of analogue values to or from differential modulation
    • H03M3/30—Delta-sigma modulation
    • H03M3/322—Continuously compensating for, or preventing, undesired influence of physical parameters
    • H03M3/358—Continuously compensating for, or preventing, undesired influence of physical parameters of non-linear distortion, e.g. instability

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Nonlinear Science (AREA)
  • General Physics & Mathematics (AREA)
  • Compression, Expansion, Code Conversion, And Decoders (AREA)

Abstract

The invention discloses a temperature sensor circuit, comprising: a bias current source; a front-end temperature sensing circuit; a sigma-delta analog-to-digital converter, comprising: the dynamic element matching logic circuit is used for eliminating element process errors in the sigma-delta analog-to-digital converter; and correcting the modulator, and eliminating intermodulation distortion by using an output bit stream control technology. The invention provides a high-precision and high-resolution temperature sensor integrated circuit solution based on a CMOS (complementary metal oxide semiconductor) process, eliminates errors caused by phenomena of component mismatch, intermodulation distortion and the like by technologies of dynamic component matching, correction, bit code stream control and the like, and remarkably improves the temperature detection precision and resolution.

Description

Temperature sensor circuit
Technical Field
The invention relates to a temperature sensor circuit, and belongs to the field of sensor integrated circuits.
Background
High-precision and high-resolution temperature sensing chip solutions based on CMOS (complementary metal oxide semiconductor) processes are needed in the fields of medical instruments, industry, scientific instruments, consumer electronics and the like. The front end of the traditional temperature sensor adopts BJT as a temperature sensing element to generate voltage which is in direct proportion to absolute temperature, a sigma-delta analog-to-digital converter is used for converting the voltage into a bit stream, and finally the voltage can be obtained by calculating the duty ratio of the bit stream and the ambient temperature can be deduced. BJTs are susceptible to bias current sources and other component mismatches that result in an overall temperature sensor with compromised resolution and reduced accuracy.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the temperature sensing element adopted by the traditional temperature sensor is easily influenced by the mismatching of a bias current source and other elements, so that the resolution and the precision of the temperature sensor are influenced.
In order to solve the above technical problem, an embodiment of the present invention provides a temperature sensor circuit, including:
a bias current source for providing a temperature-sensing circuit with a pI value bias And I bias Bias current of (a);
a front-end temperature sensing circuit connected to the bias current pI bias And I bias Post-generation voltage DeltaV BE And V BE Wherein the voltage Δ V BE Having a proportional to absolute temperature characteristic, voltage V BE Has the characteristic of decreasing with the increase of temperature;
sigma-delta analog-to-digital converter with simultaneous input of a common-mode voltage V REF And an input voltage V PTAT Then, the duty ratio of the generated bit code stream signal bs is the digital reading of the corresponding temperature, V REF ＝αΔV BE +V BE ，V PTAT ＝αΔV BE And alpha is a gain multiplying power, and is characterized by further comprising:
the dynamic element matching logic circuit is used for selecting different element combinations to be connected into the temperature sensor circuit, so that equivalent errors of the different element combinations are far smaller than errors generated by element mismatch, and therefore, element process errors in the sigma-delta analog-to-digital converter are eliminated;
and correcting the modulator, and eliminating intermodulation distortion by using an output bit stream control technology.
Preferably, the sigma-delta analog-to-digital converter is driven by two external clock signals phi with the same frequency and opposite phases 1 Phi and phi 2 Driving at phi 1 Is high level and phi 2 The sigma-delta analog-to-digital converter uses a sampling capacitor C at a low level s Collecting input voltage V PTAT . At phi 1 Is low level and phi 2 At a high powerIn normal times, the sigma-delta analog-to-digital converter can accumulate the collected charges to an integrating capacitor C of the sigma-delta analog-to-digital converter int And integrating the capacitance C int Voltage of and common mode voltage V REF By comparison, integrating capacitance C int Is greater than the common mode voltage V REF Output 1, integrating capacitor C int Is less than or equal to the common mode voltage V REF Then 0 is output, the comparator result is the output bit stream signal bs, then:
the dynamic element matching logic circuit controls (p + 1) bias current sources I bias，0 ，I bias，1 ，...，I bias，p Respectively connected with the front end temperature sensing circuit, and keeping the bias current of the front end temperature sensing circuit at a ratio of 1: p; in the current clock cycle: if bs =0, the dynamic element matching logic circuit is at φ 1 The rising edge of the bias current source changes the self state and switches the combination of the bias current source access; if bs =1, the dynamic element matching logic circuit will not change the combination of the self state and the bias current source access.
Preferably, the sigma-delta analog-to-digital converter is driven by two external clock signals phi with the same frequency and opposite phases 1 Phi and phi 2 Driving at phi 1 Is high level and phi 2 The sigma-delta analog-to-digital converter uses a sampling capacitor C at a low level s Collecting input voltage V PTAT . At phi 1 Is low level and phi 2 When the voltage is high, the sigma-delta analog-to-digital converter accumulates the collected charges to an integrating capacitor C of the sigma-delta analog-to-digital converter int And integrating the capacitance C int Voltage of and common mode voltage V REF By comparison, integrating capacitance C int Is greater than the common mode voltage V REF Output 1, integrating capacitor C int Is less than or equal to the common mode voltage V REF Then 0 is output, the comparator result is the output bit stream signal bs, then:
the correction modulator consists of a digital accumulator and a digital comparator, wherein the value of an internal register of the digital accumulator continuously increases along with the clock period and resets to zero after exceeding the maximum range; the digital comparator compares the numberThe value in the accumulator is compared with the set correction value, and the V corresponding to the BJT tube in the front-end temperature sensing circuit is controlled according to the comparison result BE As an output of the front-end temperature sensing circuit, the front-end temperature sensing circuit uses a pair of diode-connected BJTs:
in the current clock cycle: if bs =1, the digital accumulator in the correction modulator is at φ 1 The rising edge of the digital comparator carries out self-adding operation, and controls V output by the front-end temperature sensing circuit according to the comparison result of the digital comparator BE As an input to a sigma-delta analog-to-digital converter; if bs =0, the digital accumulator in the correction modulator suspends self-addition, the output result is kept unchanged, and the current V is set BE As an input to the sigma-delta analog-to-digital converter.
The invention provides a high-precision and high-resolution temperature sensor integrated circuit solution based on a CMOS (complementary metal oxide semiconductor) process, eliminates errors caused by phenomena of component mismatch, intermodulation distortion and the like by technologies of dynamic component matching, correction, bit code stream control and the like, and remarkably improves the temperature detection precision and resolution.
Drawings
FIG. 1 is a schematic diagram of the present invention;
FIG. 2 is a schematic diagram of a dynamic element matching logic circuit;
fig. 3 illustrates the switching principle of the dynamic element matching logic circuit.
Detailed Description
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.
As shown in fig. 1, the temperature sensor circuit disclosed in this embodiment includes five parts, which are a bias current source, a front-end temperature sensing circuit, a second-order sigma-delta analog-to-digital converter, a dynamic element matching logic circuit, and a correction modulator, respectively, wherein the second-order sigma-delta analog-to-digital converter, the dynamic element matching logic circuit, and the correction modulator are all driven by the same external oscillator.
The bias current source is used for providing the pI for the front-end temperature sensing circuit bias And I bias Wherein p represents a bias current magnitude ratio.
The front-end temperature sensing circuit uses a pair of diode-connected BJTs (Q1, Q2) which are connected with a bias current pI bias And I bias Generating a voltage DeltaV BE And V BE . Due to DeltaV BE And V BE Respectively has the characteristics of being in direct proportion to absolute temperature and reducing along with the increase of temperature, so that the gain multiplying power alpha with a specific size is selected to ensure that (alpha delta V) BE +V BE ) Approximately viewed as a temperature-insensitive quantity, which is denoted as the common-mode voltage V REF And will be α Δ V BE Is recorded as an input voltage V PTAT . Will common mode voltage V REF And an input voltage V PTAT And simultaneously inputting the digital data into a sigma-delta analog-to-digital converter, wherein the duty ratio of a bit code stream generated by the sigma-delta analog-to-digital converter is the digital reading of the corresponding temperature.
Because mismatch occurs when the actual size and electrical properties of the components do not match the expected values during the chip manufacturing process, the present embodiment adopts a dynamic component matching method to reduce the effect of the mismatch. The embodiment adopts a dynamic element matching logic circuit to eliminate the element process error in the sigma-delta analog-to-digital converter, and adopts an output bit code stream control technology to eliminate the intermodulation distortion.
With reference to fig. 2, the dynamic element matching logic circuit selects different element combinations to be connected into the circuit, so that the equivalent error of different element combinations is much smaller than the error generated by element mismatch. The dynamic element matching logic circuit is essentially a state machine controlled by its current state and external inputs. In FIG. 2, the dynamic element matching logic circuit controls (p + 1) bias current sources I by taking the bias current source part as an example bias，0 ，I bias，1 ，...，I bias，p Are respectively connected with two BJTs and keep the ratio of the bias current of the BJTs to be about 1: p. And phi 1 Phi and phi 2 Are two external clock signals of the same frequency and opposite phase that drive the sigma-delta analog-to-digital converter (the same applies below). In thatφ 1 Is high level and phi 2 The sigma-delta analog-to-digital converter uses a sampling capacitor C at a low level s Collecting input voltage V PTAT . At phi 1 Is low level and phi 2 When the voltage is high, the sigma-delta analog-to-digital converter accumulates the collected charges to an integrating capacitor C of the sigma-delta analog-to-digital converter int And integrating the capacitance C int Voltage of and common mode voltage V REF By comparison, the integrating capacitance C int Is greater than the common mode voltage V REF Then output 1, integrating capacitor C int Is less than or equal to the common mode voltage V REF Then 0 is output, and the result of the comparator is the output bit stream signal bs. In connection with fig. 3, in the current clock cycle: if bs =0, the dynamic element matching logic circuit will be at φ 1 The rising edge of the switching element changes the state of the switching element and switches the combination of the access of the bias current source; if bs =1, the dynamic element matching logic circuit will not change the combination of the self state and the bias current source access.
The correction modulator can be realized by a self-adder, meets the requirement of calibration precision, and also eliminates intermodulation distortion by applying an output bit stream control technology. In this embodiment, the correction modulator is essentially comprised of a digital accumulator and a digital comparator. The value on the internal register of the digital accumulator will self-increment with clock cycles and reset to zero after the maximum range is exceeded. The digital comparator compares the value in the digital accumulator with the set correction value, and controls the V corresponding to the BJT tube according to the comparison result BE As the output of the front end temperature sensing circuit. In the current clock cycle: if bs =1, the digital accumulator in the correction modulator will be at φ 1 The rising edge of the digital comparator carries out self-adding operation, and controls V output by the front-end temperature sensing circuit according to the comparison result of the digital comparator BE As an input to a sigma-delta analog-to-digital converter; if bs =0, the digital accumulator in the correction modulator suspends self-addition, the output result is kept unchanged, and the current V is set BE As an input to the sigma-delta analog-to-digital converter.
The dynamic element matching technology element adopted by the invention eliminates the influence of first-order error generated by mismatched elements in an averaging mode. The dynamic element matching logic circuit and the correction modulator controlled by the bit code stream ensure that the frequency spectrum of the output bit code stream has no mutually offset wave peak, thereby avoiding the influence of noise on the quality of low-frequency spectrum band signals.

Claims (3)

1. A temperature sensor circuit, comprising:
a bias current source for providing pI for the front-end temperature sensing circuit bias And I bias Bias current of (d);
a front-end temperature sensing circuit connected to the bias current pI bias And I bias Post-generation voltage Δ V BE And V BE Wherein the voltage is Δ V BE Having a proportional to absolute temperature characteristic, voltage V BE Has the characteristic of decreasing with increasing temperature;
sigma-delta analog-to-digital converter with simultaneous input of a common-mode voltage V REF And an input voltage V PTAT Then, the duty ratio of the generated bit code stream signal bs is the digital reading of the corresponding temperature, V REF ＝αΔV BE +V BE ，V PTAT ＝αΔV BE And alpha is a gain multiplying power, and is characterized by further comprising:
the dynamic element matching logic circuit is used for selecting different element combinations to be connected into the temperature sensor circuit, so that equivalent errors of the different element combinations are far smaller than errors generated by element mismatch, and element process errors in the sigma-delta analog-to-digital converter are eliminated;
and correcting the modulator, and eliminating intermodulation distortion by using an output bit stream control technology.
2. A temperature sensor circuit according to claim 1, wherein said sigma-delta analog-to-digital converter is operated by two external clock signals phi of the same frequency and opposite phase 1 Phi and phi 2 Driving at phi 1 Is high level and phi 2 When the level is low, the sigma-delta A/D converter uses the sampling capacitor C s Collecting input voltage V PTAT . In phi 1 Is low level and phi 2 When the voltage is high, the sigma-delta analog-to-digital converter accumulates the collected chargesIntegrating capacitor C of integrating sigma-delta analog-to-digital converter int And integrating the capacitance C int Voltage of and common mode voltage V REF By comparison, integrating capacitance C int Is greater than the common mode voltage V REF Output 1, integrating capacitor C int Is less than or equal to the common mode voltage V REF Then 0 is output, the comparator result is the output bit stream signal bs, then:
the dynamic element matching logic circuit controls (p + 1) bias current sources I bias，0 ，I bias，1 ，...，I bias，p Respectively connected with the front-end temperature sensing circuit, and keeping the bias current of the front-end temperature sensing circuit at a ratio of 1: p; in the current clock cycle: if bs =0, the dynamic element matching logic circuit is at φ 1 The rising edge of the switching element changes the state of the switching element and switches the combination of the access of the bias current source; if bs =1, the dynamic element matching logic circuit will not change the combination of the self state and the bias current source access.
3. A temperature sensor circuit according to claim 1, wherein said sigma-delta analog-to-digital converter is operated by two external clock signals phi of the same frequency and opposite phase 1 Phi and phi 2 Driving at phi 1 Is high level and phi 2 The sigma-delta analog-to-digital converter uses a sampling capacitor C at a low level s Collecting input voltage V PTAT . At phi 1 Is low level and phi 2 When the voltage is high level, the sigma-delta analog-to-digital converter accumulates the collected charges to an integrating capacitor C of the sigma-delta analog-to-digital converter int And integrating the capacitance C int Voltage of and common mode voltage V REF By comparison, the integrating capacitance C int Is greater than the common mode voltage V REF Output 1, integrating capacitor C int Is less than or equal to the common mode voltage V REF Then 0 is output, the comparator result is the output bit stream signal bs, then:
the correction modulator comprises a digital accumulator and a digital comparator, wherein the value of the internal register of the digital accumulator increases with the clock period and exceeds the maximum valueReset to zero after a large range; the digital comparator compares the value in the digital accumulator with the set correction value, and controls the V corresponding to the BJT tube in the front-end temperature sensing circuit according to the comparison result BE As an output of the front-end temperature sensing circuit, the front-end temperature sensing circuit uses a pair of diode-connected BJTs:
in the current clock cycle: if bs =1, the digital accumulator in the correction modulator is at φ 1 The rising edge of the digital comparator performs self-adding operation, and controls the V output by the front-end temperature sensing circuit according to the comparison result of the digital comparator BE As an input to a sigma-delta analog-to-digital converter; if bs =0, the digital accumulator in the correction modulator suspends self-addition, the output result is kept unchanged, and the current V is set BE As input to the sigma-delta analog-to-digital converter.
CN202211069692.6A 2022-09-02 2022-09-02 Temperature sensor circuit Pending CN115452177A (en)

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Application Number Priority Date Filing Date Title
CN202211069692.6A CN115452177A (en) 2022-09-02 2022-09-02 Temperature sensor circuit

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