Design Of CMOS Temperature Sensor With Digital Calibration

The advancement of science and technology has made more and more demand for the application of information measurement,and in modern society,cold chain transportation,environmental monitoring,scientific experiments,etc.All need to use temperature sensors for temperature measurement.There are many types of temperature sensors,among them,the temperature sensor based on CMOS process has the advantages of fast measurement speed,wide temperature measurement range,small size,low cost and high durability.The modern CMOS process is mature,and the products produced by the CMOS process have good stability,easy to use and can be used in conjunction with other electronic devices to achieve industrial and commercial needs.So that CMOS temperature sensors have a wide range of applications in military,aerospace,science and technology,medical,agricultural and other fields.Based on the 0.6μm CMOS process of Huahong Hongli,this paper completes the chip design of a CMOS temperature sensor,and the temperature sensor circuit mainly includes two parts:temperature sensing circuit andΣ-ΔADC.According to the characteristics that the V_BEandΔV_BEproduced by the bipolar transistors at different current densities have different temperature characteristics,the two voltages are quantified byΣ-ΔADC to obtain the transfer function of the temperature sensor,and finally the digital output code representing the temperature is obtained through the processing of the digital circuit block.In order to improve the temperature measurement accuracy of CMOS temperature sensor,based on the analysis of the error generated by the temperature sensing circuit,the dynamic device matching and input offset storage techniques are used to reduce the error generated by the temperature sensing circuit.Due to the slower temperature change in practical applications,which requires higher area and accuracy of the chip,a first-order sigma-delta ADC is used for quantization.Improving the temperature measurement accuracy of CMOS temperature sensors usually requires additional correction method,and a new correction method based on digital circuits is proposed and adopted.This method corrects the error of the temperature sensor and eliminates the temperature measurement error of the temperature sensor due to process mismatch by modifying the counter and state machine in the digital module of the temperature sensor.Compared with the circuit using the analog correction method,the circuit realized based on the proposed correction method can achieve a similar temperature measurement effect without adding additional correction devices,and compared with the CMOS temperature sensing circuit using the existing digital correction method,the temperature measurement accuracy is improved to a certain extent.The chip simulation and actual measurement show that the chip area is 1.6mm²,under the working voltage of 2.7V～5.5V,in the working range of-55℃-125℃,the chip has a resolution of 0.0625℃;the pre-imitation error is 0.375℃;the post-imitation error is 1.0625℃;and the maximum measured error of the tapeout is1.83℃.