Research On Automatic Calibration System Of CMOS Temperature Sensor Chip Based On FPGA

The application of temperature sensing chip has penetrated into the electric power,metallurgy,chemical industry,building materials,machinery,food,petroleum and other industries.People have higher and higher requirements on the precision of temperature measurement,which requires the precision test and calibration of the chip developed.Firstly,the overall design strategy of the high precision Complementary Metal Oxide Semiconductor temperature sensor was analyzed in this thesis.The main causes of errors in the temperature sensor of the Bipolar Junction Transistor based on CMOS process are analyzed.The?V_BE errors between the two PNP pairs in the temperature sensing circuit of the BJT tube will increase with the increase of the ambient temperature of the object to be measured.In order to control the?V_BE error,thus improve the accuracy of temperature measurement.On the one hand,it is necessary to control from the hardware circuit,such as reducing errors in the design of devices;Join the control circuit,on the other hand,put forward a kind of temperature sensor automatic calibration technology,the technology is based on fast voltage calibration method,micro control unit,successive approximation algorithm of calibration resistance network,the traditional manual calibration technology improvement for automatic calibration technology for industrialized mass production,effectively reduce the calibration cost.Then,in order to verify the effectiveness of the automatic calibration technology proposed in this thesis,under the global foundries 0.18?m standard CMOS process,participated in the circuit design,layout drawing,tape-out,experimental environment building and chip testing of CMOS temperature sensor including temperature sensing front end,delta sigma ADC,calibration circuit and digital control circuit.In addition,in order to solve the problem of temperature fluctuation in the process of testing,this thesis also proposes a method to build a high precision and high stability testing environment.Finally,according to the automatic calibration circuit designed in this thesis,the logic design of the automatic calibration algorithm is completed,and it is programmed,simulated and verified.After passing the verification,the FPGA is used to burn the board.The experimental results show that the error of CMOS temperature sensor is less than 0.1? after 2 seconds of automatic calibration at room temperature.