A low power temperature sensor circuit
By combining a bandgap reference with a positive temperature current generation circuit, and using a simple operational amplifier structure, the problems of large size and high power consumption of traditional temperature sensors are solved, achieving low power consumption and high precision temperature detection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 58TH RES INST OF CETC
- Filing Date
- 2026-03-09
- Publication Date
- 2026-05-29
AI Technical Summary
Traditional temperature sensors suffer from large size, high cost, and high power consumption. In particular, when integrated on a chip, they affect the accuracy of temperature detection, and the complex circuitry increases the design difficulty.
By employing a bandgap reference and a positive temperature current generation circuit, combined with a temperature sensing core circuit, a startup circuit, a current reference circuit, and a buffer circuit, temperature detection is achieved through a simple operational amplifier structure, avoiding the use of complex ADC circuits.
This reduces circuit power consumption, simplifies design, and improves the accuracy and reliability of temperature detection.
Smart Images
Figure CN122108376A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of integrated circuit technology, and in particular to a low-power temperature sensor circuit.
[0002] Background Area
[0003] With the rapid development of modernization, the requirements for automated measurement are constantly increasing, and temperature sensors play a crucial role in this process, being applied in various fields such as environmental monitoring, medical equipment, industrial control, automotive electronics, and logistics. Traditional temperature sensors typically rely on discrete components, such as resistance temperature detectors (RTDs) and thermocouples. These discrete components are often too large for on-chip integration, typically requiring off-chip structures. This not only increases costs but also affects the accuracy of temperature detection due to the different environments in which the discrete components and the chip operate. Therefore, on-chip temperature sensors have developed rapidly, offering advantages such as low power consumption and small size.
[0004] In recent years, various new on-chip temperature sensors have emerged. To achieve high-precision temperature detection, complex circuits such as ADC (Analog to Digital Converter) are usually added to the circuit for temperature data processing. This not only increases the difficulty of circuit design, but also results in higher power consumption. Summary of the Invention
[0005] To address the above problems, this invention provides a low-power temperature sensor circuit.
[0006] The solution to achieve the purpose of this invention is: a low-power temperature sensor circuit, including a temperature sensing core circuit, and a startup circuit, a current reference circuit, and a buffer circuit connected to the temperature sensing core circuit;
[0007] The core temperature sensing circuit consists of a bandgap reference and a positive temperature current generating circuit. The PTAT current generated by the bandgap reference is superimposed with the positive temperature current generated by the positive temperature current generating circuit to produce a voltage proportional to temperature. The startup circuit consists of a Schmitt trigger startup circuit and a bandgap reference startup circuit to prevent latch-up effect during power-on. The current reference circuit uses a voltage-controlled current source to provide a stable, load-independent current. The buffer circuit uses a two-stage operational amplifier source follower configuration. The first stage uses a differential-to-single-ended diode as a common-source amplifier structure for the load, and the second stage uses a current source as a common-source amplifier structure for the load.
[0008] Furthermore, the temperature sensing core circuit includes a first operational amplifier, two parallel bipolar PNP transistors, resistors R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, and MOS transistors M1, M2, M3, M4, M5, M6, M7, M8, M9, M10, M11, M12, M13, M14, M15, M16, M17, M18, M19, M20, M21, M22;
[0009] The drain of MOS transistor M1 is connected to the drain and source of M2, and the source of MOS transistor M3 is connected to the drain of MOS transistor M3, the drain of M6, and one end of resistor R1; the drain of MOS transistor M5 is connected to the source of M6.
[0010] The gates of MOS transistors M2, M5, M11, M14, M16, M18, and M20, as well as one end of resistor R6, are connected to provide a stable voltage bias for the core temperature sensing circuit.
[0011] The gates of MOS transistors M6, M8, M12, M15, and M17, the gate and drain of M9, and one end of resistor R2 are connected to generate a self-biased voltage.
[0012] The other end of resistor R1 is connected to the drain of MOS transistor M4; the other end of resistor R2 is connected to the drain of MOS transistor M10.
[0013] The drain of MOS transistor M11 is connected to the source of M12; the drain of MOS transistor M12 is connected to one end of resistors R3 and R4.
[0014] The other end of resistor R3 is connected to the emitter of bipolar PNP transistor Q1; the other end of resistor R4 is connected to one end of resistor R5 and the positive input terminal of the first operational amplifier.
[0015] The drain of MOS transistor M14 is connected to the source of M15; the drain of MOS transistor M15 is connected to one end of resistor R7 and the emitter of bipolar PNP transistor Q2.
[0016] The other end of resistor R7 and one end of resistor R8 are connected to the negative input terminal of the first operational amplifier;
[0017] The drain of MOS transistor M16 is connected to the source of M17; one end of resistor R9 is connected to one end of resistor R10.
[0018] The sources of MOS transistors M1, M5, M7, M8, M11, M14, M16, M18 and M20 are connected to the power supply terminal Vph;
[0019] The sources of MOS transistors M4, M10, M21, and M22, the collectors of bipolar PNP transistors Q1 and Q2, and the other ends of resistors R5, R8, and R10 are grounded.
[0020] The drain of MOS transistor M18 is connected to the source of M19; the gate of MOS transistor M19 is grounded, and its drain is used as a current output terminal for the first operational amplifier; the drain of MOS transistor M20 is used as another current output terminal for the first operational amplifier.
[0021] The drain of MOS transistor M17 is connected to the other end of resistor R9 and the drain of MOS transistor M21, serving as the output terminal of the temperature sensing core circuit for use by the startup circuit and the buffer circuit.
[0022] Furthermore, the first operational amplifier is a common-source, common-gate differential operational amplifier; the bipolar PNP transistor is a temperature sensing device;
[0023] The first operational amplifier includes MOS transistors M23, M24, M25, M26, M27, M28, M29, M30, M31, M32, M33, M34, M35, M36, and M37;
[0024] The gate and drain of MOS transistor M23 are connected to the gate of MOS transistor M27 and the drain of MOS transistor M24, generating a self-biased voltage.
[0025] The gates of MOS transistors M24 and M28 are connected to the gate and drain of transistor M35, generating a self-biased voltage. Vc is derived from the current output provided by the temperature sensing core circuit.
[0026] The source of MOS transistor M24 is connected to the drain of M25 and the drain of M26; the source of MOS transistor M28 is connected to the drain of M29 and the drain of M31.
[0027] The sources of MOS transistors M25 and M29 are connected to the drain of M30;
[0028] The gates of MOS transistors M30 and M34 are connected to the drain of MOS transistor M33, generating a self-biased voltage. Vb comes from another current output provided by the temperature sensing core circuit.
[0029] The gates of MOS transistors M26, M31, and M32 are connected to the control signal Pd to control the turning on or off of the first operational amplifier.
[0030] The gates of MOS transistors M25 and M33 serve as the positive input terminals of the first operational amplifier; the gate of MOS transistor M29 serves as the negative input terminal of the first operational amplifier.
[0031] The source of MOS transistor M33 is connected to the drain of M34; the source of MOS transistor M35 is connected to the drain and gate of M36, and MOS transistor M36 forms a diode structure.
[0032] The source of MOS transistor M36 and the drain and gate of M37 are connected, and MOS transistor M37 forms a diode structure.
[0033] The sources of MOS transistors M23 and M27 are connected to the power supply terminal Vph;
[0034] The sources of MOS transistors M26, M30, M31, M32, M34, and M37 are grounded;
[0035] The drains of MOS transistors M27 and M28 are connected to form the output of the first operational amplifier.
[0036] Furthermore, the buffer circuit includes a second operational amplifier, resistors R11 and R12, and capacitors C1 and C2. The negative input terminal of the second operational amplifier is connected to the output terminal of the second operational amplifier, forming a source follower structure. Resistors R11 and capacitor C1 and resistors R12 and capacitor C2 form two low-pass filters.
[0037] Furthermore, the second operational amplifier includes MOS transistors M38, M39, M40, M41, M42, M43, M44, M45, M46, resistors R13, R14, R15, R16, and capacitor C3.
[0038] The gate of MOS transistor M38 is connected to one end of resistors R14 and R15, and the resistors provide a bias voltage through voltage division; the drain of MOS transistor M38 is connected to one end of resistor R13.
[0039] The gate and drain of MOS transistor M39 are connected to the gates of MOS transistors M42 and M46, as well as the other end of resistor R13, to generate a self-biased voltage.
[0040] The gate and drain of MOS transistor M40 are connected to the gate of MOS transistor M43 and the drain of M41; the source of MOS crystals M41 and M44 is connected to the drain of M42.
[0041] The gate of MOS transistor M41 serves as the negative input terminal of the second operational amplifier; the gate of MOS transistor M44 serves as the positive input terminal of the second operational amplifier.
[0042] The drains of MOS crystals M43 and M44 and the gate of M45 are connected to one end of capacitor C3; the other end of capacitor C3 is connected to one end of resistor R16.
[0043] The source of MOS transistors M38, M40, M43, and M45 and the other end of resistor R14 are connected to the power supply terminal Vph; the source of MOS transistors M39, M42, and M46 is grounded.
[0044] The drains of MOS transistors M45 and M46 are connected to the other end of resistor R16, serving as the output of the second operational amplifier.
[0045] Furthermore, the current reference circuit includes a third operational amplifier, MOS transistors M47, M48, M49, M50, M51, M52, M53, M54, M55, M56, M57, M58, M59, M60, M61, M62 and resistor R17.
[0046] The positive input terminal of the third operational amplifier is connected to Vref_bias, which is provided by the temperature sensing core circuit, and the negative input terminal is connected to the drain of the MOS transistor M48 and one end of the resistor R17.
[0047] The output terminal of the third operational amplifier is connected to the gate of MOS transistors M47, M49, and M52.
[0048] The drain of MOS transistor M47 is connected to the source of M48; the gate and drain of MOS transistor M55 are connected to the gates of MOS transistors M48, M55, and M62, as well as the drain of M56, generating a self-biased voltage.
[0049] The drains of MOS transistors M49 and M50 are connected to the gates of MOS transistors M50, M51, M53, and M59, generating a self-biased voltage.
[0050] The source of MOS transistor M50 is connected to the drain of M51.
[0051] The drains of MOS transistors M52 and M53 are connected to the gates of MOS transistors M54, M56, and M60, generating a self-biased voltage.
[0052] The source of MOS transistor M53 is connected to the drain of M54.
[0053] The drain of MOS transistor M57 is connected to the source of M58; the gates of MOS transistors M57 and M61 are connected to the drains of M58 and M59.
[0054] The source of MOS transistor M59 is connected to the drain of M60; the drain of MOS transistor M61 is connected to the source of M62.
[0055] The source of MOS transistors M47, M49, M52, M55, M57, and M61 is connected to the power supply terminal Vph.
[0056] The sources of MOS transistors M51, M54, M56, and M60 are grounded;
[0057] The drain of the MOS transistor M62 serves as the output terminal of the current reference circuit.
[0058] Furthermore, the third operational amplifier includes MOS transistors M63, M64, M65, M66, M67, M68, M69, M70, M71, M72, M73, M74, M75, M76, M77, M78, M79, M80, M81, M82, M83 and resistor R18;
[0059] The drain of MOS transistor M63 is connected to the gates of M63, M65, and M73, as well as one end of resistor R18, to generate a self-biased voltage; the other end of resistor R18 is connected to the drain of MOS transistor M64.
[0060] The drains of MOS transistors M65 and M66 are connected to the gates of M66, M68, M71, M75, M78, and M82.
[0061] The drains of MOS transistors M67 and M68 are connected to the gates of M67, M70, and M81; the sources of MOS transistors M69 and M70 are connected.
[0062] The gates of MOS transistors M69 and M80 are connected to the gates of M70 and M71; the source of MOS transistor M71 is connected to the drain of M72.
[0063] The drain of MOS transistor M73 is connected to the source of M74 and M77; the gate of MOS transistor M74 serves as the positive input terminal of the third operational amplifier; the gate of MOS transistor M77 serves as the negative input terminal of the third operational amplifier.
[0064] The drains of MOS transistors M74 and M75 are connected to the gates of M72 and M76; the source of MOS transistor M75 is connected to the drain of M76.
[0065] The drains of MOS transistors M77 and M78 are connected to the gates of M79 and M83; the source of MOS transistor M78 is connected to the drain of M79.
[0066] The drain of MOS transistor M80 is connected to the source of M81; the source of MOS transistor M82 is connected to the drain of M83.
[0067] The source of MOS transistors M63, M65, M67, M69, M73, and M80 and the gate of M64 are connected to the power supply terminal Vph.
[0068] The sources of MOS transistors M64, M66, M68, M72, M76, M79, and M83 are grounded;
[0069] The drains of MOS transistors M81 and M82 serve as the output terminals of the third operational amplifier.
[0070] Furthermore, the startup circuit includes a Schmitt trigger startup circuit and a bandgap reference startup circuit.
[0071] Furthermore, the Schmitt trigger startup circuit includes MOS transistors M84, M85, M86, M87, M88, and M89 to prevent latch-up during power-on.
[0072] The gates of MOS transistors M84, M85, M86, and M87 are connected to the input of the Schmitt trigger start-up circuit, and Vref is provided by the temperature sensing core circuit.
[0073] The drains of MOS transistors M84 and M88 are connected to the source of M85; the source of MOS transistors M86 and M89 is connected to the drain of M87.
[0074] The source of MOS transistor M84 and the drain of M89 are connected to the low power supply terminal Vp; the source of MOS transistor M87 and the drain of M88 are grounded.
[0075] The drains of MOS transistors M85 and M86 are connected to the gates of MOS transistors M88 and M89, serving as the output terminals of the Schmitt trigger start-up circuit.
[0076] Furthermore, the bandgap reference startup circuit includes MOS transistors M90 and M91;
[0077] The gate of the MOS transistor M91 serves as the input terminal of the bandgap reference startup circuit and is connected to the output terminal of the Schmitt trigger startup circuit.
[0078] The gate of MOS transistor M90 is connected to the control signal Pd_n; the source of MOS transistor M90 is connected to the power supply terminal Vph; the source of MOS transistor M91 is grounded.
[0079] The drain terminals of MOS crystals M90 and M91 are connected, serving as the output terminal of the bandgap reference start-up circuit.
[0080] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention does not require complex circuits such as ADC for temperature data processing, but only realizes the temperature detection of the chip through bandgap reference and positive temperature generation circuit, which reduces the design difficulty of the circuit and reduces the power consumption of the circuit. Attached Figure Description
[0081] Figure 1 A circuit diagram of a low-power temperature sensor provided for an embodiment of the present invention.
[0082] Figure 2 This is a circuit diagram of the first operational amplifier in the temperature sensing core circuit of this invention.
[0083] Figure 3 This is a circuit diagram of the second operational amplifier in the buffer circuit of an embodiment of the present invention.
[0084] Figure 4 This is a current reference circuit diagram in an embodiment of the present invention.
[0085] Figure 5 This is a circuit diagram of the third operational amplifier in the current reference circuit of this invention.
[0086] Figure 6 This is a circuit diagram of the startup circuit in an embodiment of the present invention. Detailed Implementation
[0087] like Figure 1 As shown, this invention proposes a low-power temperature sensor circuit, including: a temperature sensing core circuit, a startup circuit, a current reference circuit, and a buffer circuit. The temperature sensing core circuit consists of a bandgap reference and a positive temperature current generation circuit. The PTAT current generated by the bandgap reference is superimposed with the positive temperature current generated by the positive temperature current generation circuit to produce a voltage proportional to temperature. The startup circuit consists of a Schmitt trigger startup circuit and a bandgap reference startup circuit, preventing latch-up during power-up. The current reference circuit uses a voltage-controlled current source to provide a stable, load-independent current, and its high output impedance provides effective isolation. The buffer circuit uses a simple two-stage operational amplifier source follower configuration. The first stage uses a differential-to-single-ended diode as a load common-source amplifier structure, and the second stage uses a current source as a load common-source amplifier structure to achieve a wide output voltage swing. This invention eliminates the need for complex circuits such as an ADC for temperature data processing, achieving chip temperature detection solely through the bandgap reference and the positive temperature generation circuit, reducing circuit design complexity and power consumption.
[0088] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that the drawings are all in a simplified form and are not to a precise scale, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.
[0089] This invention provides a low-power temperature sensor circuit, the circuit diagram of which is shown below. Figure 1 As shown, it includes a temperature sensing core circuit, a startup circuit, a current reference circuit, and a buffer circuit. The temperature sensing core circuit consists of a bandgap reference and a positive temperature current generating circuit. The positive temperature current generating circuit is connected to the bandgap reference, which generates a PTAT current. The positive temperature current generating circuit generates a positive temperature current, which is superimposed with the PTAT current to obtain temperature data, which is then output by the buffer circuit.
[0090] The core temperature sensing circuit includes a first operational amplifier, two bipolar PNP transistors, resistors R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, and MOS transistors M1, M2, M3, M4, M5, M6, M7, M8, M9, M10, M11, M12, M13, M14, M15, M16, M17, M18, M19, M20, M21, and M22. The bipolar PNP transistors are temperature sensing devices. The circuit diagram of the first operational amplifier is shown below. Figure 2 As shown, the structure is a common-source cascode differential operational amplifier. The operational amplifier is the key to the bandgap reference. Through its negative feedback mechanism, it ultimately forces the voltages at its two input terminals, Vip and Vin, to be approximately equal, accurately establishing and locking a voltage proportional to the absolute temperature. Moreover, a high-gain operational amplifier can greatly improve the PSRR of the bandgap reference circuit, especially in the low-frequency range.
[0091] In the embodiments of the present invention, please refer to the reference. Figure 1 and Figure 3The buffer circuit includes a second operational amplifier, resistors R11 and R12, and capacitors C1 and C2. The negative input terminal of the second operational amplifier is connected to the output terminal of the second operational amplifier to form a source follower structure. Resistors R11 and capacitor C1 and resistors R12 and capacitor C2 form two low-pass filters. It should be noted that the second operational amplifier includes MOS transistors M38, M39, M40, M41, M42, M43, M44, M45, and M46, resistors R13, R14, R15, and R16, and capacitor C3. The gate of MOS transistor M38 is connected to one end of resistors R14 and R15, providing a bias voltage through resistor division. The drain of MOS transistor M38 is connected to one end of resistor R13. The gate and drain of MOS transistor M39 are connected to the gates of MOS transistors M42 and M46, as well as the other end of resistor R13, generating a self-bias voltage. The gate and drain of MOS transistor M40 are connected to the gate of MOS transistor M43 and the drain of M41. The sources of M41 and M44 are connected to the drain of M42. The gate of MOS transistor M41 serves as the negative input of the second operational amplifier, and the gate of MOS transistor M44 serves as the positive input of the second operational amplifier. The drains of MOS transistors M43 and M44, the gate of M45, and one end of capacitor C3 are connected. The other end of capacitor C3 is connected to one end of resistor R16. The sources of MOS transistors M38, M40, M43, and M45 and the other end of resistor R14 are connected to the power supply terminal Vph. The sources of MOS transistors M39, M42, and M46 are grounded. The drains of MOS transistors M45 and M46 and the other end of resistor R16 are connected, serving as the output of the second operational amplifier. Furthermore, it should be noted that C3 is the Miller compensation capacitor and R16 is the zero-adjustment resistor. The core function of the Miller compensation capacitor is frequency compensation, preventing self-oscillation and ensuring stable amplifier operation. For a multi-stage amplifier, each stage generates a pole. When two or more pole frequencies are very close, at the frequency point where the loop gain drops to 1, the phase lag may reach or exceed 180°, leading to worse negative feedback and positive feedback, thus causing self-oscillation. Miller compensation, through a capacitor, "reshapes" the frequency response of the amplifier to meet the Barkhausen stability criterion, that is, when the open-loop gain drops to 0dB, the phase margin is large enough. However, Miller compensation has a key side effect: it introduces a right half-plane zero. The zero-adjustment resistor is precisely to solve the side effect of Miller compensation. Its core function is to cancel or move the harmful zero introduced by the Miller capacitor, further improving stability.
[0092] Regarding the selection of the zero-adjustment resistor R16, ideally, to completely cancel out the second pole, the resistor value should be set as follows:
[0093] (1)
[0094] In formula (1) It is the transconductance of the output stage amplifier tube.
[0095] Further, in this embodiment of the invention, the current reference circuit includes a third operational amplifier, MOS transistors M47, M48, M49, M50, M51, M52, M53, M54, M55, M56, M57, M58, M59, M60, M61, M62, and resistor R17, as shown in the circuit diagram below. Figure 4 As shown. It should be noted that the positive input terminal of the third operational amplifier is connected to Vref_bias, provided by the temperature sensing core circuit; the negative input terminal is connected to the drain of MOS transistor M48 and one end of resistor R17; the output terminal of the third operational amplifier is connected to the gates of MOS transistors M47, M49, and M52; the drain of MOS transistor M47 is connected to the source of M48; the gate and drain of MOS transistor M55 are connected to the gates of MOS transistors M48, M55, and M62, and the drain of M56, generating a self-biased voltage; the drains of MOS transistors M49 and M50 are connected to the gates of MOS transistors M50, M51, M53, and M59, generating a self-biased voltage; and the source of MOS transistor M50 is connected to the drain of M51. The drains of MOS transistors M52 and M53 are connected to the gates of MOS transistors M54, M56, and M60, generating a self-biased voltage. The source of MOS transistor M53 is connected to the drain of M54. The drain of MOS transistor M57 is connected to the source of M58. The gates of MOS transistors M57 and M61 are connected to the drains of M58 and M59. The source of MOS transistor M59 is connected to the drain of M60. The drain of MOS transistor M61 is connected to the source of M62. The sources of MOS transistors M47, M49, M52, M55, M57, and M61 are connected to the power supply terminal Vph. The sources of MOS transistors M51, M54, M56, and M60 are grounded. The drain of MOS transistor M62 serves as the output terminal of the current reference circuit. Furthermore, it should be noted that the third operational amplifier in the current reference circuit adopts a negative feedback connection to form a negative feedback loop, which forces the voltages at the two input terminals of the operational amplifier to be equal, thereby accurately setting and stabilizing the output current, making it almost unaffected by power supply voltage fluctuations, load changes, and transistor parameter deviations.
[0096] The third operational amplifier in the current reference circuit, such as Figure 5As shown. The third operational amplifier includes MOS transistors M63, M64, M65, M66, M67, M68, M69, M70, M71, M72, M73, M74, M75, M76, M77, M78, M79, M80, M81, M82, and M83, and resistor R18. The drain of MOS transistor M63 and the gates of M63, M65, and M73, as well as one end of resistor R18, are connected to generate a self-biased voltage. The other end of resistor R18 is connected to the MOS transistors... The drain of M64 is connected to the gate of MOS transistors M65 and M66, and the gates of M66, M68, M71, M75, M78, and M82 are connected to the gate of MOS transistors M67 and M68, and the gates of M67, M70, and M81 are connected to the gate of MOS transistors M69 and M70. The gates of MOS transistors M69 and M80 are connected to the gates of M70 and M71. The source of MOS transistor M71 is connected to the drain of M72. The drain of MOS transistor M73 is connected to the gate of M64. The gate of MOS transistor M74 is connected to the source of M74 and M77. The gate of MOS transistor M74 serves as the positive input terminal of the third operational amplifier, and the gate of MOS transistor M77 serves as the negative input terminal of the third operational amplifier. The drains of MOS transistors M74 and M75 are connected to the gates of M72 and M76. The source of MOS transistor M75 is connected to the drain of M76. The drains of MOS transistors M77 and M78 are connected to the gates of M79 and M83. The source of MOS transistor M78 is connected to the source of M79 and M83. The drains of transistors M79 and M80 are connected together. The drain of MOS transistor M80 is connected to the source of M81. The source of MOS transistor M82 is connected to the drain of M83. The sources of MOS transistors M63, M65, M67, M69, M73, and M80, and the gate of M64 are connected to the power supply terminal Vph. The sources of MOS transistors M64, M66, M68, M72, M76, M79, and M83 are grounded. The drains of MOS transistors M81 and M82 serve as the output terminals of the third operational amplifier. It should be noted that the essence of its design lies in achieving a balance between gain, swing, bandwidth, and power consumption.
[0097] In an embodiment of the present invention, the startup circuit includes a Schmitt trigger startup circuit and a bandgap reference startup circuit, the circuit of which is as follows: Figure 6 As shown.
[0098] The Schmitt trigger startup circuit includes MOS transistors M84, M85, M86, M87, M88, and M89, preventing latch-up upon power-up. The gates of MOS transistors M84, M85, M86, and M87 are connected to the input of the Schmitt trigger startup circuit. Vref is provided by the temperature sensing core circuit. The drains of MOS transistors M84 and M88 are connected to the source of M85. The sources of MOS transistors M86 and M89 are connected to the drain of M87. The source of MOS transistors M84 and the drain of M89 are connected to the low power supply terminal Vp. The source of MOS transistors M87 and the drain of M88 are grounded. The drains of MOS transistors M85 and M86 are connected to the gates of MOS transistors M88 and M89, serving as the output of the Schmitt trigger startup circuit.
[0099] The bandgap reference startup circuit includes MOS transistors M90 and M91, ensuring normal startup of the bandgap reference. The gate of MOS transistor M91 serves as the input terminal of the bandgap reference startup circuit and is connected to the output terminal of the Schmitt trigger startup circuit. The gate of MOS transistor M90 is connected to the control signal Pd_n, the source of MOS transistor M90 is connected to the power supply terminal Vph, and the source of MOS transistor M91 is grounded. The drain terminals of MOS transistors M90 and M91 are connected and serve as the output terminal of the bandgap reference startup circuit.
[0100] To make the objectives, technical approaches, and advantages of the specific embodiments of this application clearer, the technical approaches in the specific embodiments of this application will be described more clearly and completely below. Unless otherwise defined, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art.
[0101] Combined with reference Figure 1 — Figure 6 The low-power temperature sensor circuit described in this embodiment of the invention includes: a temperature sensing core circuit, a startup circuit, a current reference circuit, and a buffer circuit. The temperature sensing core circuit senses the temperature, generates a PTAT current and a positive temperature current, and superimposes these two currents to obtain the temperature data. The temperature sensing core circuit is divided into a bandgap reference circuit and a positive temperature current generation circuit, such as... Figure 1 As shown. It should be noted that the function of the bipolar PNP transistor in the bandgap reference is to convert the external temperature signal into a one-to-one voltage signal. The ratio of the emitter junction area of the bipolar PNP transistor Q1 to that of the bipolar PNP crystal Q2 in the circuit is 8:1. The first operational amplifier in the bandgap reference is a common-source, common-gate differential operational amplifier, as shown... Figure 2As shown, the operational amplifier (op-amp) provides two paths for the bandgap reference: positive feedback and negative feedback. Through the negative feedback mechanism, the op-amp continuously adjusts its output voltage, thereby adjusting the currents I1 and I2 provided by M11 and M14. Ultimately, this forces the voltages at the two input terminals V+ and V- to be equal. The op-amp forces the voltages across resistors R4 and R7 to be equal. Since the resistance values of all resistors are the same and the currents I1 and I2 are equal, the voltage drop across resistor R3 is exactly equal to the voltage drop across the two bipolar PNP transistors. Difference:
[0102] (2)
[0103] In formula (2) For two bipolar PNP transistors difference, This is the base-emitter voltage of the bipolar PNP transistor Q2. This is the base-emitter voltage of the bipolar PNP transistor Q1. is the thermal voltage, and N is the ratio of the emitter junction area of bipolar PNP transistor Q1 to that of bipolar PNP crystal Q2.
[0104] PTAT current The expression is:
[0105] (3)
[0106] According to formula (3) The current is replicated to the Vref voltage generation circuit through the current mirror.
[0107] Bandgap reference output voltage The expression is:
[0108] (4)
[0109] Substituting formulas (2) and (3) into formula (4), we get:
[0110] (5)
[0111] In formula (5), N is the ratio of the emitter areas of bipolar PNP transistors Q1 and Q2, and N = 8.
[0112] like Figure 1 As shown, the current flowing through MOS transistor M21 is I3, which is obtained from the reference current provided by the current reference circuit via the positive temperature current generation circuit. It should be noted that the ratio of the number of MOS transistors M21 to M22 connected in parallel is 1:2.
[0113] The expression for the temperature sensing voltage PTC_out is:
[0114] (6)
[0115] Substituting formula (5) into formula (6) and simplifying, we get:
[0116] (7)
[0117] The temperature sensing voltage PTC_out has good positive temperature characteristics. After the buffer enhances its load-carrying capacity, it will be used as the final temperature sensing output voltage of this design.
[0118] Buffer circuit reference Figure 1 The operational amplifier is connected in a source follower configuration. The second operational amplifier circuit of the buffer is as follows: Figure 3 As shown, the second operational amplifier has a two-stage structure, with Miller capacitors and zero-adjustment resistors added to enhance circuit stability. The buffer's main functions are signal isolation and enhancing the load-carrying capacity of the temperature-sensing voltage PTC_out. It should be noted that an RC low-pass filter network is connected at both the input and output of the source follower, its function being to anti-aliasing, limit the input noise bandwidth, and prevent capacitive load oscillation.
[0119] Current reference circuit, such as Figure 4 As shown, the current reference circuit includes a third operational amplifier. The third operational amplifier in the current reference circuit adopts a negative feedback connection to form a negative feedback loop, which forces the voltages at the two input terminals of the operational amplifier to be equal, thereby accurately setting and stabilizing the output current, making it almost unaffected by power supply voltage fluctuations, load changes and transistor parameter deviations.
[0120] The circuit diagram of the third operational amplifier is as follows: Figure 5 As shown, the third operational amplifier has a two-stage structure. Unlike the second operational amplifier, the second stage of the third operational amplifier is a common-source common-gate structure, and the first stage is no longer a simple five-transistor operational amplifier, which ensures higher gain and thus accurately sets and stabilizes the output current of the current reference circuit.
[0121] Start-up circuit such as Figure 6 As shown, the startup circuit includes a Schmitt trigger startup circuit and a bandgap reference startup circuit. The Schmitt trigger startup circuit prevents latch-up during power-on, while the bandgap reference startup circuit ensures the normal startup and operation of the bandgap reference.
[0122] In summary, this invention provides a low-power temperature sensor circuit that achieves chip temperature detection through simple circuits such as a temperature sensing core circuit, a buffer circuit, a current reference circuit, and a startup circuit. It eliminates the need for complex circuits such as an ADC for temperature data processing, reducing circuit design complexity and power consumption.
[0123] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A low-power temperature sensor circuit, characterized in that, It includes a temperature sensing core circuit, as well as a startup circuit, a current reference circuit, and a buffer circuit connected to the temperature sensing core circuit. The core temperature sensing circuit consists of a bandgap reference and a positive temperature current generating circuit. The PTAT current generated by the bandgap reference is superimposed with the positive temperature current generated by the positive temperature current generating circuit to generate a voltage that is proportional to the temperature. The starting circuit consists of a Schmitt trigger starting circuit and a bandgap reference starting circuit to prevent latch-up effect when powered on. The current reference circuit uses a voltage-controlled current source to provide a stable, load-independent current. The buffer circuit uses a two-stage operational amplifier source follower configuration. The first stage uses a differential-to-single-ended diode as the load common source amplifier structure, and the second stage uses a current source as the load common source amplifier structure.
2. The low-power temperature sensor circuit according to claim 1, characterized in that, The temperature sensing core circuit includes a first operational amplifier, two parallel bipolar PNP transistors, resistors R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, and MOS transistors M1, M2, M3, M4, M5, M6, M7, M8, M9, M10, M11, M12, M13, M14, M15, M16, M17, M18, M19, M20, M21, M22; The drain of MOS transistor M1 is connected to the drain and source of M2, and the source of MOS transistor M3 is connected to the drain of MOS transistor M3, the drain of M6, and one end of resistor R1; the drain of MOS transistor M5 is connected to the source of M6. The gates of MOS transistors M2, M5, M11, M14, M16, M18, and M20, as well as one end of resistor R6, are connected to provide a stable voltage bias for the temperature sensing core circuit. The gates of MOS transistors M6, M8, M12, M15, and M17, the gate and drain of M9, and one end of resistor R2 are connected to generate a self-biased voltage. The other end of resistor R1 is connected to the drain of MOS transistor M4; the other end of resistor R2 is connected to the drain of MOS transistor M10. The drain of MOS transistor M11 is connected to the source of M12; the drain of MOS transistor M12 is connected to one end of resistors R3 and R4. The other end of resistor R3 is connected to the emitter of bipolar PNP transistor Q1; the other end of resistor R4 is connected to one end of resistor R5 and the positive input terminal of the first operational amplifier. The drain of MOS transistor M14 is connected to the source of M15; the drain of MOS transistor M15 is connected to one end of resistor R7 and the emitter of bipolar PNP transistor Q2. The other end of resistor R7 and one end of resistor R8 are connected to the negative input terminal of the first operational amplifier; The drain of MOS transistor M16 is connected to the source of M17; one end of resistor R9 is connected to one end of resistor R10. The sources of MOS transistors M1, M5, M7, M8, M11, M14, M16, M18 and M20 are connected to the power supply terminal Vph; The sources of MOS transistors M4, M10, M21, and M22, the collectors of bipolar PNP transistors Q1 and Q2, and the other ends of resistors R5, R8, and R10 are grounded. The drain of MOS transistor M18 is connected to the source of M19; the gate of MOS transistor M19 is grounded, and its drain is used as a current output terminal for the first operational amplifier; the drain of MOS transistor M20 is used as another current output terminal for the first operational amplifier. The drain of MOS transistor M17 is connected to the other end of resistor R9 and the drain of MOS transistor M21, serving as the output terminal of the temperature sensing core circuit for use by the startup circuit and the buffer circuit.
3. The low-power temperature sensor circuit according to claim 2, characterized in that, The first operational amplifier is a common-source, common-gate differential operational amplifier; the bipolar PNP transistor is a temperature sensing device; The first operational amplifier includes MOS transistors M23, M24, M25, M26, M27, M28, M29, M30, M31, M32, M33, M34, M35, M36, and M37; The gate and drain of MOS transistor M23 are connected to the gate of MOS transistor M27 and the drain of MOS transistor M24, generating a self-biased voltage. The gates of MOS transistors M24 and M28 are connected to the gate and drain of transistor M35, generating a self-biased voltage. Vc is derived from the current output provided by the temperature sensing core circuit. The source of MOS transistor M24 is connected to the drain of M25 and the drain of M26; the source of MOS transistor M28 is connected to the drain of M29 and the drain of M31. The sources of MOS transistors M25 and M29 are connected to the drain of M30; The gates of MOS transistors M30 and M34 are connected to the drain of MOS transistor M33, generating a self-biased voltage. Vb comes from another current output provided by the temperature sensing core circuit. The gates of MOS transistors M26, M31, and M32 are connected to the control signal Pd to control the turning on or off of the first operational amplifier. The gates of MOS transistors M25 and M33 serve as the positive input terminals of the first operational amplifier; the gate of MOS transistor M29 serves as the negative input terminal of the first operational amplifier. The source of MOS transistor M33 is connected to the drain of M34; the source of MOS transistor M35 is connected to the drain and gate of M36, and MOS transistor M36 forms a diode structure. The source of MOS transistor M36 and the drain and gate of M37 are connected, and MOS transistor M37 forms a diode structure. The sources of MOS transistors M23 and M27 are connected to the power supply terminal Vph; The sources of MOS transistors M26, M30, M31, M32, M34, and M37 are grounded; The drains of MOS transistors M27 and M28 are connected to form the output of the first operational amplifier.
4. The low-power temperature sensor circuit according to claim 1, characterized in that, The buffer circuit includes a second operational amplifier, resistors R11 and R12, and capacitors C1 and C2. The negative input terminal of the second operational amplifier is connected to the output terminal of the second operational amplifier, forming a source follower structure. Resistors R11 and capacitor C1 and resistors R12 and capacitor C2 form two low-pass filters.
5. The low-power temperature sensor circuit according to claim 4, characterized in that, The second operational amplifier includes MOS transistors M38, M39, M40, M41, M42, M43, M44, M45, M46, resistors R13, R14, R15, R16, and capacitor C3; The gate of MOS transistor M38 is connected to one end of resistors R14 and R15, and the resistors provide a bias voltage through voltage division; the drain of MOS transistor M38 is connected to one end of resistor R13. The gate and drain of MOS transistor M39 are connected to the gates of MOS transistors M42 and M46, as well as the other end of resistor R13, to generate a self-biased voltage. The gate and drain of MOS transistor M40 are connected to the gate of MOS transistor M43 and the drain of M41; the source of MOS crystals M41 and M44 is connected to the drain of M42. The gate of MOS transistor M41 serves as the negative input terminal of the second operational amplifier; the gate of MOS transistor M44 serves as the positive input terminal of the second operational amplifier. The drains of MOS crystals M43 and M44 and the gate of M45 are connected to one end of capacitor C3; the other end of capacitor C3 is connected to one end of resistor R16. The source of MOS transistors M38, M40, M43, and M45 and the other end of resistor R14 are connected to the power supply terminal Vph; the source of MOS transistors M39, M42, and M46 is grounded. The drains of MOS transistors M45 and M46 are connected to the other end of resistor R16, serving as the output of the second operational amplifier.
6. The low-power temperature sensor circuit according to claim 1, characterized in that, The current reference circuit includes a third operational amplifier, MOS transistors M47, M48, M49, M50, M51, M52, M53, M54, M55, M56, M57, M58, M59, M60, M61, M62 and resistor R17. The positive input terminal of the third operational amplifier is connected to Vref_bias, which is provided by the temperature sensing core circuit, and the negative input terminal is connected to the drain of the MOS transistor M48 and one end of the resistor R17. The output terminal of the third operational amplifier is connected to the gate of MOS transistors M47, M49, and M52. The drain of MOS transistor M47 is connected to the source of M48; the gate and drain of MOS transistor M55 are connected to the gates of MOS transistors M48, M55, and M62, as well as the drain of M56, generating a self-biased voltage. The drains of MOS transistors M49 and M50 are connected to the gates of MOS transistors M50, M51, M53, and M59, generating a self-biased voltage. The source of MOS transistor M50 is connected to the drain of M51. The drains of MOS transistors M52 and M53 are connected to the gates of MOS transistors M54, M56, and M60, generating a self-biased voltage. The source of MOS transistor M53 is connected to the drain of M54. The drain of MOS transistor M57 is connected to the source of M58; The gates of MOS transistors M57 and M61 are connected to the drains of M58 and M59. The source of MOS transistor M59 is connected to the drain of M60; the drain of MOS transistor M61 is connected to the source of M62. The source of MOS transistors M47, M49, M52, M55, M57, and M61 is connected to the power supply terminal Vph. The sources of MOS transistors M51, M54, M56, and M60 are grounded; The drain of the MOS transistor M62 serves as the output terminal of the current reference circuit.
7. The low-power temperature sensor circuit according to claim 6, characterized in that, The third operational amplifier includes MOS transistors M63, M64, M65, M66, M67, M68, M69, M70, M71, M72, M73, M74, M75, M76, M77, M78, M79, M80, M81, M82, M83 and resistor R18; The drain of MOS transistor M63 is connected to the gates of M63, M65, and M73, as well as one end of resistor R18, to generate a self-biased voltage; the other end of resistor R18 is connected to the drain of MOS transistor M64. The drains of MOS transistors M65 and M66 are connected to the gates of M66, M68, M71, M75, M78, and M82. The drains of MOS transistors M67 and M68 are connected to the gates of M67, M70, and M81; the sources of MOS transistors M69 and M70 are connected. The gates of MOS transistors M69 and M80 are connected to the gates of M70 and M71; the source of MOS transistor M71 is connected to the drain of M72. The drain of MOS transistor M73 is connected to the source of M74 and M77; the gate of MOS transistor M74 serves as the positive input terminal of the third operational amplifier; the gate of MOS transistor M77 serves as the negative input terminal of the third operational amplifier. The drains of MOS transistors M74 and M75 are connected to the gates of M72 and M76; the source of MOS transistor M75 is connected to the drain of M76. The drains of MOS transistors M77 and M78 are connected to the gates of M79 and M83; the source of MOS transistor M78 is connected to the drain of M79. The drain of MOS transistor M80 is connected to the source of M81; the source of MOS transistor M82 is connected to the drain of M83. The source of MOS transistors M63, M65, M67, M69, M73, and M80 and the gate of M64 are connected to the power supply terminal Vph. The sources of MOS transistors M64, M66, M68, M72, M76, M79, and M83 are grounded; The drains of MOS transistors M81 and M82 serve as the output terminals of the third operational amplifier.
8. The low-power temperature sensor circuit according to claim 1, characterized in that, The startup circuit includes a Schmitt trigger startup circuit and a bandgap reference startup circuit.
9. The low-power temperature sensor circuit according to claim 8, characterized in that, The Schmitt trigger startup circuit includes MOS transistors M84, M85, M86, M87, M88, and M89 to prevent latch-up during power-on. The gates of MOS transistors M84, M85, M86, and M87 are connected to the input of the Schmitt trigger start-up circuit, and Vref is provided by the temperature sensing core circuit. The drains of MOS transistors M84 and M88 are connected to the source of M85; the source of MOS transistors M86 and M89 is connected to the drain of M87. The source of MOS transistor M84 and the drain of M89 are connected to the low power supply terminal Vp; the source of MOS transistor M87 and the drain of M88 are grounded. The drains of MOS transistors M85 and M86 are connected to the gates of MOS transistors M88 and M89, serving as the output terminals of the Schmitt trigger start-up circuit.
10. The low-power temperature sensor circuit according to claim 8, characterized in that, The bandgap reference start-up circuit includes MOS transistors M90 and M91; The gate of the MOS transistor M91 serves as the input terminal of the bandgap reference startup circuit and is connected to the output terminal of the Schmitt trigger startup circuit. The gate of the MOS transistor M90 is connected to the control signal Pd_n; The source of MOS transistor M90 is connected to the power supply terminal Vph; the source of MOS transistor M91 is grounded. The drain terminals of MOS crystals M90 and M91 are connected, serving as the output terminal of the bandgap reference start-up circuit.