Research And Design Of CMOS Temperature Sensor

Temperature sensors are indispensable in medical device,consumer electronics,industrial contol and other fields.Compared to the traditional temperature sensors,integrated CMOS temperature sensors have smaller volume and lower power consumption,and also easy to integrate and can be directly connected to the digital system.Their application prospect will be more extensive in the future.The CMOS temperature sensor designed in this paper is implemented by TSMC 65nm LP CMOS process.The CMOS temperature sensor convert the voltage-difference precisely to the digital output of temperature using a AD converter,based on that voltage-difference of base-emitter voltage between two parasitic bipolar transistor which are biased at different current densities is proportional to the absolute temperature.This paper analyzes the temperature characteristics of parasitic bipolar transistor under the CMOS process,and discusses the error caused by various non-ideal factors of temperature sensor in detail,including the error caused by nonlinearity of VBE,limited current gain and disorders(including the disorder of operational amplifier and the disorder of current mirror),and then gives the corresponding solution.The current bias circuit is employed to solve the limited current gain,chopper technology is employed to solve the disorder of operational amplifier,dynamic matching technology(DEM)is employed to solve the disorder of current mirror.Because of the low requirement of the speed and the high requirement of the precision of temperature measurement,A 12 bit first-order sigma-delta ADC is employed to quantize,the integrator in sigma-delta ADC uses two stage operational amplifier with gain-boosting.The simulation result shows that the low-frequency gain of the operational amplifier is 107dB.The area of the chip is 0.588mm×0.536mm.The power supply is 1.2V,the input reference clock is 400kHz.The post-simulation results show that the core power consumption is 1.25mW,the measurement error is within ±0.47? in the temperature range of 0?-60? under the TT corner,the measurement error is within ±1.46? in the temperature range of 0?-60? under the SS and FF corner.