Research And Design Of Temperature Sensor Based On SAR ADC

The function of temperature sensor includes measuring and controlling temperature,and its application range is very wide,including electronic products,industry,medical instruments,etc.Therefore,many researchers are devoted to the research of temperature sensor.At present,the integrated temperature sensor has become one of the research hotspots due to its advantages of small size and high precision.The temperature measurement range of the existing temperature sensor is roughly-70～+200℃.Compared with this,the temperature sensor in this paper has a larger temperature measurement range and can be adapted to the measurement of extreme temperatures.The temperature sensor in this paper consists of two parts: the temperature sensing circuit and the SAR ADC circuit.The temperature sensing circuit is designed based on the PTAT characteristics of bipolar transistors,and uses dynamic matching technology to reduce mismatch,chopper technology to reduce noise,and switched capacitor amplifiers to set voltage amplification.The SAR ADC circuit consists of sample and hold circuit,comparator,SAR logic and DAC capacitor array.By adopting the principle of level recovery to improve the TSPC register that constitutes the SAR logic circuit,the competition between signals can be avoided,and the SAR ADC circuit can work normally under high temperature.In order to reduce the area,the DAC capacitor array is designed with a 6+6 segmented structure.The sample and hold circuit adopts the gate voltage bootstrap structure to improve the linearity of the circuit.The whole circuit can complete the function of converting the temperature signal into a digital signal.In this paper,the 0.18μm process is used to design the overall circuit and layout,the layout area is 723.97μm×581.48μm,the temperature measurement range of the circuit is-150～200℃,and the sensitivity is about 4.9m V/℃.Set the power supply voltage to 3.3V.In the previous simulation,within the temperature measurement range,the circuit accuracy is-2.5/+4.8℃,and at room temperature,the circuit power consumption is 9.76 m W.In the post-simulation,the circuit accuracy drops to-7.6/+16.9℃,and the circuit power consumption is 11.62 m W at room temperature.In the post simulation,due to the accuracy of SAR ADC decreases at high temperature,the overall circuit accuracy decreases to-7.6/+16.9 ℃,and the circuit power consumption is 11.62 m W at room temperature.