A temperature sensor based on gate leakage current of MOS transistor

Abstract

The present application belongs to the field of analog integrated circuits, and relates to a temperature sensor in an integrated circuit, in particular to a temperature sensor based on a gate leakage current of a MOS transistor. The present application utilizes the gate leakage current of a MOS transistor, and makes the current flow through the MOS transistor working in a sub-threshold region, so as to generate a CTAT voltage. Since the gate leakage current is extremely small, the power consumption of the temperature sensing front end is extremely low. Since a linear relationship between the output signal and the threshold voltage is established, and the threshold voltage has a strong linear relationship with temperature in a wide temperature range, the circuit structure is simple, and a wide temperature sensing range and high temperature linearity are also ensured. Meanwhile, the present application has high scalability, and different quantization modules can be used in different application scenarios according to performance requirements to meet corresponding requirements, which is conducive to realizing high-precision temperature sensing integrated in a chip.

Description

Technical Field

[0001] This invention belongs to the field of analog integrated circuits and relates to temperature sensors in integrated circuits, specifically a temperature sensor based on the gate leakage current of a MOS transistor. Background Technology

[0002] Temperature, as a crucial environmental factor, has a significant impact on the performance parameters of electronic devices. Therefore, temperature sensors are needed to convert temperature signals into identifiable electrical signals for monitoring and control. Temperature sensors can be categorized into traditional discrete temperature sensors, such as those based on thermistors or thermocouples, and emerging integrated circuit temperature sensors.

[0003] Traditional discrete temperature sensors are typically bulky, making them inconvenient to integrate into micro-devices or chips. Integrated circuit (IC) temperature sensors, on the other hand, can be manufactured on integrated circuits using semiconductor processes, achieving smaller size and higher integration, which is beneficial for further improving chip performance. Furthermore, IC temperature sensors offer advantages such as low power consumption, fast response, low cost, and high scalability. Therefore, research on IC temperature sensors is of great significance for advancing microelectronics technology and intelligent devices.

[0004] Integrated circuit sensors can be mainly classified into BJT-type temperature sensors, resistive temperature sensors, and MOS-type temperature sensors. BJT-type temperature sensors often use ADC quantization, offering advantages such as high accuracy and a wide sensing range, but their circuit structure is complex and power consumption is relatively high. Resistive temperature sensors also frequently use ADC quantization, striking a balance between power consumption and accuracy, but typically suffer from a larger area. MOS-type temperature sensors often use FDC quantization, offering advantages such as a small overall circuit and low power consumption, but compared to BJT and resistive temperature sensors, their accuracy and sensing range are somewhat inferior. Summary of the Invention

[0005] To address the aforementioned problems or shortcomings, this invention provides a temperature sensor based on MOSFET gate leakage current. Because the gate leakage current is extremely small, the current of the temperature sensing circuit is only on the order of pA, thus enabling low-power measurement over a wide temperature sensing range.

[0006] A temperature sensor based on the gate leakage current of MOS transistors includes NMOS transistors M1 and M3 and PMOS transistors M2 and M4.

[0007] The NMOS transistor M1 and PMOS transistor M2 form a temperature sensing circuit, generating a voltage with a negative temperature coefficient, i.e., the CTAT output voltage. M1 is connected as a MOS capacitor, generating gate leakage current. M2 is a PMOS transistor operating in the subthreshold region. The current in the entire temperature sensing circuit is determined by M1, which is connected as a MOS capacitor. M1 and M2 together generate the CTAT voltage, i.e., V. CTAT .

[0008] The NMOS transistor M3 and PMOS transistor M4 form a compensation circuit. M3, an NMOS transistor, is connected as a MOS capacitor, and M4, a PMOS transistor, operates in the subthreshold region. M3 and M4 serve as the voltage reference for replication, diverting the substrate current of M1 to the replicated voltage reference to prevent the substrate current of M1 from affecting V. CTAT The temperature linearity is affected.

[0009] Furthermore, the specific connection method of the MOS transistors M1, M3, M2, and M4 is as follows:

[0010] The gate of M1 is connected to the power supply voltage VDD. The source and drain of M1 are connected together and connected to the source of M2. This port is the output terminal of the temperature sensing circuit. The substrate of M1 is connected to the source, drain and substrate of M3 and connected to the source of M4.

[0011] The gate and drain of M2 are connected and grounded, and the substrate is connected to the power supply voltage VDD; the gate of M3 is connected to the power supply voltage VDD; the gate and drain of M4 are connected and grounded, and the substrate is connected to the power supply voltage VDD.

[0012] The voltage signal V output by the temperature sensing circuit CTAT This is the output of the entire temperature sensor.

[0013] Furthermore, M2 and M4 employ small-sized MOS transistors, enabling them to operate in the subthreshold region.

[0014] Furthermore, the output voltage signal V CTAT Depending on the requirements, quantization can be performed directly using an ADC; or it can be converted into a time or frequency signal through a conversion module and then quantized using TDC or FDC.

[0015] In summary, this invention utilizes the gate leakage current of a MOSFET for temperature sensing. This current flows through the MOSFET operating in the subthreshold region, generating a CTAT voltage. Because the gate leakage current is extremely small, very low power consumption is ensured at the temperature sensing front end. Since a linear relationship is established between the output signal and the threshold voltage, and the threshold voltage exhibits a strong linear relationship with temperature over a wide temperature range, a wide temperature sensing range and high temperature linearity are guaranteed while maintaining a simple circuit structure. Furthermore, this invention offers high scalability; different quantization modules can be used in different application scenarios to meet specific performance requirements, facilitating high-precision temperature sensing when integrated within a chip. Attached Figure Description

[0016] Figure 1 This is a structural block diagram of the present invention.

[0017] Figure 2 This is a schematic diagram of the circuit structure for an embodiment.

[0018] Figure 3 This is a schematic diagram illustrating the relationship between output voltage and temperature in an embodiment. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0020] The temperature sensor based on the gate leakage current of a MOS transistor provided in this embodiment includes two parts: a temperature sensing circuit and a compensation circuit.

[0021] M1 is an NMOS transistor connected as a MOS capacitor, generating gate leakage current. M2 is a PMOS transistor operating in the subthreshold region. The current in the entire temperature sensing circuit is determined by M1 connected as a MOS capacitor. M1 and M2 together generate the CTAT voltage, i.e., V. CTAT .

[0022] M3 is an NMOS transistor, and M4 is a PMOS transistor, serving as the voltage reference for replication. The substrate current of M1 is diverted to this replica voltage reference to prevent the substrate current of M1 from affecting V. CTAT The temperature linearity is affected.

[0023] The gate of M1 is connected to the power supply voltage VDD. The source and drain of M1 are connected together and connected to the source of M2. This port is the output terminal of the temperature sensing circuit. The substrate of M1 is connected to the source, drain, and substrate of M3 and connected to the source of M4. The gate and drain of M2 are connected to ground and the substrate is connected to the power supply voltage VDD. The gate of M3 is connected to the power supply voltage VDD. The gate and drain of M4 are connected to ground and the substrate is connected to the power supply voltage VDD.

[0024] The voltage signal V output by the temperature sensing circuit CTATThis is the output of the entire temperature sensor.

[0025] The working principle of the temperature sensor will be analyzed in detail below.

[0026] The gate leakage current of the MOSFET in the temperature sensing circuit is shown in formula (1):

[0027]

[0028] Where I OX V is the gate leakage current of the MOSFET; K2 and α are process parameters; W is the width of the MOSFET channel; V GS T is the voltage difference between the gate and source of the MOSFET; OX I represents the thickness of the gate oxide layer. From the formula, we can see that... ox It is a temperature-independent current, but it will change with V. GS It changes with the changes.

[0029] The subthreshold current of the MOSFET is given by formula (2):

[0030]

[0031] Where I D β is the gate-source current of the MOSFET; β = μC ox W / L, μ is the carrier mobility, C ox Here, W / L represents the gate oxide capacitance per unit area, and W / L is the width-to-length ratio of the MOSFET; n = 1 + C D / C ox C D It is the depletion layer capacitance under the channel; V T =KT / q, where K is Boltzmann's constant, T is temperature, and q is the amount of charge; V TH V is the threshold voltage of the MOSFET; DS This represents the voltage difference between the drain and source of the MOSFET.

[0032] Since M2 is a diode connection, its V GS =V DS And when V DS ≥3V T At that time, V DS to I D The impact is negligible, therefore I D It can be simplified to formula (3):

[0033]

[0034] M1 and M2 are in the same branch, so the gate leakage current of M1 is equal to the subthreshold current of M2. By combining equations (1) and (3) and taking the logarithm of both sides of the equation, we can obtain equation (4):

[0035]

[0036] V can be obtained by simplification. GS The expression is shown in formula (5):

[0037]

[0038] From formula (1), we can see that I ox A quantity independent of temperature, which only varies with V GS It changes with the change. Let I0 = β(n-1)V T 2 .

[0039] Experiments have shown that within the temperature range of -55℃ to 125℃, V TH It has a linear relationship with T, and the V of PMOS TH It has a positive temperature coefficient, therefore V TH This can be expressed as formula (6):

[0040] V TH (T)=V TH (T0)+K TH (T-T0) (6)

[0041] V TH (T0) is the threshold voltage measured at temperature T0, K TH It is V TH The temperature coefficient is positive.

[0042] For V GS Differentiation yields formula (7):

[0043]

[0044] Because V TH For V GS The main part, therefore K TH As a determining factor of formula (7), Since it is positive, the final value V is obtained. GS It has a linear relationship with temperature.

[0045] Based on the circuit diagram shown, we have formula (8):

[0046] V GS =0-V out =-V out (8)

[0047] Therefore, the output signal V of the temperature sensor out =-V GS It has a negative temperature coefficient, namely V. CTAT,like Figure 3 As shown.

[0048] At the same time, to avoid the substrate current of M1 affecting V GS The temperature linearity is affected, so the substrate current needs to be extracted. At the same time, in order to avoid the potential difference between the substrate and the source of M1 being too large, M3 and M4 are used as the voltage reference for replication, and the substrate current of M1 is extracted to the branch where M3 and M4 are located.

[0049] As can be seen from the above embodiments, this invention utilizes the gate leakage current of a MOSFET, allowing this current to flow through the MOSFET operating in the subthreshold region, thereby generating a CTAT voltage. Because the gate leakage current is extremely small, very low power consumption is ensured at the temperature sensing front end. Since a linear relationship is established between the output signal and the threshold voltage, and the threshold voltage exhibits a strong linear relationship with temperature over a wide temperature range, a wide temperature sensing range and high temperature linearity are guaranteed while maintaining a simple circuit structure. Furthermore, it offers high scalability; different quantization modules can be used in different application scenarios to meet specific performance requirements, facilitating high-precision temperature sensing when integrated within a chip.

Claims

1. A temperature sensor based on the gate leakage current of a MOSFET, characterized in that: Including NMOS transistors M1 and M3 and PMOS transistors M2 and M4; The NMOS transistor M1 and PMOS transistor M2 form a temperature sensing circuit, generating a voltage with a negative temperature coefficient, i.e., the CTAT output voltage. M1 is connected as a MOS capacitor, generating gate leakage current. M2 is a PMOS transistor operating in the subthreshold region. The current in the entire temperature sensing circuit is determined by M1, which is connected as a MOS capacitor. M1 and M2 together generate the CTAT voltage, i.e., V. CTAT ; The NMOS transistor M3 and PMOS transistor M4 form a compensation circuit. M3, an NMOS transistor, is connected as a MOS capacitor, and M4, a PMOS transistor, operates in the subthreshold region. M3 and M4 serve as the voltage reference for replication, diverting the substrate current of M1 to the replicated voltage reference to prevent the substrate current of M1 from affecting V. CTAT The temperature linearity is affected; The specific connection methods of the MOS transistors M1, M3, M2 and M4 are as follows: The gate of M1 is connected to the power supply voltage VDD. The source and drain of M1 are connected together and connected to the source of M2. This port is the output terminal of the temperature sensing circuit. The substrate of M1 is connected to the source, drain and substrate of M3 and connected to the source of M4. The gate and drain of M2 are connected and grounded, and the substrate is connected to the power supply voltage VDD; the gate of M3 is connected to the power supply voltage VDD; the gate and drain of M4 are connected and grounded, and the substrate is connected to the power supply voltage VDD. The voltage signal V output by the temperature sensing circuit CTAT This is the output of the entire temperature sensor.

2. The temperature sensor based on the gate leakage current of a MOSFET as described in claim 1, characterized in that: M2 and M4 are small-sized MOS transistors, which enable them to operate in the subthreshold region.

3. The temperature sensor based on the gate leakage current of a MOSFET as described in claim 1, characterized in that: The output voltage signal V CTAT Depending on the requirements, quantization can be performed directly using an ADC; or it can be converted into a time or frequency signal through a conversion module and then quantized using TDC or FDC.

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