The Design Of The Temperature Sensor And Research

This thesis focus on the study and design of an digital output, integrated temperature sensor which is fabricated in XFAB0.6um BICMOS process, accuracy of±0.5℃(single-point calibration) in the range of0℃-60℃The characteristics of the temperature sensor does not require additional calibration, the sensor can output digital temperature directly via a digital interface. The main application field of consumer electronics such as mobile phones.The temperature sensor consists mainly of the temperature sensor,the sigma delta modulation, the digital filter section as well as data communication interface section. This thesis is focused on the previous three parts.Temperature sensor designed in this paper is mainly based on that the difference base-emitter voltage between two transistors which are biased at different current densities is PTAT, and sigma delta ADC can converts the PTAT voltage accurately to the real-time chip local temperature.This thesis discusses the error source in the temperature sensor, and gives the corresponding feasible solution which mainly include VBE nonlinear, the calibration of VBE offset, as well as a variety of disorder elimination (including op amp, switch injection mismatch and device mismatch). The elimination of Op-amp offset mainly use the chopper technology, the matching of key parameters use the dynamic matching (DEM) technology. The oversampling features of Sigma delta modulator and the above two techniques can be well compatible, and because of no excessive demands of the speed of the temperature measurement (10times/sec has gone far enough)in practical applications, the use of sigma delta converter can achieve very high accuracy. Taking the cost and simplicity of the circuit into account,this thesis designed a first order discrete sigma delta converter which has a ENOB of13-bit.meeting the measurement requirements in the temperature sensor. The fluctuations in VBE can take advantage of calibration techniques based on the bitstream, and the nonlinear of VBE can be controlled in the acceptable range by the introduction of certain positive temperature coefficient to the reference source (indirect reference source).