Research And Design Of High-performance Digital Temperature Sensor Detection Circuit

The application requirements of temperature sensors in various daily temperature measurements are increasing with the rapid development of the Internet of Things and 5G communication technology,especially high-performance digital temperature sensors.For the traditional digital temperature sensor,it is difficult to balance the requirements of accuracy,speed,measurement range and low cost.This paper studies and designs a temperature detection circuit suitable for high-performance digital temperature sensors based on the 0.18?m BCD process by using a variety of error cancellation techniques and digital trimming methods.It is mainly divided into two modules:temperature sensing circuit and temperature-digital conversion circuit.Main operating principle:A temperature sensing circuit with a bipolar transistor?BJT?as the core temperature sensing element can convert the actual temperature into a variable of analog voltage?V_BE.Then,a temperature-to-digital conversion circuit operated by a sigma-delta ADC converts the change in?V_BE into a digital code output.In this paper,the voltage-current temperature characteristics of BJT,the generation of the major error sources in the temperature detection circuit and the related error calculation have been analyzed.In order to improve the overall accuracy,a variety of error cancellation techniques are used in the circuit.Such as current mirror dynamic matching?DEM?,chopper stabilization technology,BJT limited current gain elimination technology and curvature compensation technology in temperature sensing circuits.The temperature-to-digital conversion circuit uses two-phase non-overlapping clocks,dynamic capacitor matching and automatic zero calibration,etc.In order to enhance the reliability of the circuit,the power-on stability of the temperature-sensing circuit is analyzed in detail.By setting proper feedback,it can work stably without start-up circuit.In addition,the article also compares two different sigma-delta modulators with capacitive interface methods and their impact on overall accuracy.Compared with the traditional analog trimming method,this paper uses a simpler single temperature point digital calibration method to reduce the trimming cost after packaging.The temperature detection circuit uses a substrate-type PNP transistor as the core temperature sensing element to be compatible with a standard CMOS process.The post-simulation results show that the accuracy of the digital temperature sensor with capacitance DEM can achieve±0.5°C in the range of-55°C?150°C after single-point digital calibration.In the range of-15°C?100°C,its accuracy can achieve±0.2°C.Monte Carlo post-simulation results show that the temperature error of the digital temperature sensor with capacitance DEM is within-0.8°C?1°C?3??in the range of-40°C?150°C,after a single-point digital calibration at 20°C.The test results after tape-out show that after single-point digital calibration the accuracy of the digital temperature sensor with capacitance DEM can achieve±1°C in the range of-40°C?150°C.The digital temperature sensors without capacitance DEM have an accuracy of±1.2°C in the range of-30°C to 100°C.The single conversion time of both is about 12.3ms.The chip core area of both is about 0.22mm².