Design Of Integrated Temperature Sensor Interface Circuit

As an important monitoring node for detecting sensor collaboration network,temperature sensing has been widely used in industrial process control,medical equipment,intelligent home,and other fields.With the continuous development of semiconductor technology and the expansion of the mobile consumer electronics market,people have gradually realized that the necessity of miniature integrated temperature sensing equipment.However,since the traditional temperature sensor interface circuit has difficulty in meeting the requirements of the modern monitoring environment,performance indicators such as integrability and low power consumption for the system of temperature sensor interface circuits are gradually increased.By investigates and analyzes the operation principles and performance indicators of temperature sensor interface circuits at home and abroad,this paper researches and designs an integrated temperature sensor interface circuit.Using the model-selection of temperature sensing devices as a departure point,the temperature characteristics of longitudinal parasitic bipolar transistors under CMOS technology are studied,and the main source of non-ideal errors in front-end temperature sensing modules are analyzed.By means of chopping wave stabilization and DEM,the impact of operational amplifier noise offset and current mirror mismatch on temperature measurement accuracy is eliminated.Making use of the threshold exponential characteristic of the BJT current gain,the higher-order temperature linear term of the V_BE is compensated and curvature compensation is achieved.The front-end temperature sensing module circuit collects the voltage V_BE andΔV_BE with temperature characteristics,and converts the temperature signals into analog signals.The back-end circuit uses a 10-bit SAR ADC to quantify the output digital signal.Among them,the DAC adopts a segmented capacitor structure of low 4 bits and high 6 bits,and the comparator adopts a high-speed structure of three-stage pre-amplification plus one-stage latch cascade.The dynamic latch method is used in the SAR logic control circuit to reduce power consumption.This thesis is based on the SMIC 0.18μm CMOS to build and simulate the temperature sensor interface circuit.The simulation results show that the chopper-op-amp gain is 89.44d B and the low frequency noise is 71.83n V/sqrt（Hz）when the power supply voltage is 1.8V,the temperature coefficient of the core temperature sensing circuit is 1.7808m V/°C;10-bit SAR ADC sampling rate is 10k S/s,effective number of bits is 9.0119,SNR is 59.3256d B,SFDR is 68.7091d B,THD is-62.5859d B;the temperature sensor interface circuit is-50°C～+125°C,the relative temperature measurement error is±0.47°C,the resolution is 0.2°C/LSB,and the overall average power consumption is 434.9μW.