CMOS数字热真空传感器芯片设计

Design of CMOS Digital Thermal Vacuum Sensor Chip

基于标准CMOS工艺设计了一款集成热真空传感器、运算放大器、逐次逼近型模数转换器(SAR ADC)、数字信号处理电路的传感器系统。工作在恒电流模式的传感器,气压敏感区间为1～105Pa。运算放大器(OPAMP)的输入级采用互补差分对获得轨至轨的共模输入范围。为满足精度要求,对SAR ADC中数模转换器电容阵列进行优化设计,并采用输出失调存储技术消除比较器的失调电压。数字电路采用查表法将电压信号变换为气压值。结果表明:运算放大器能无失真地驱动200Ω电阻,模数转换器的有效位为9.5 bit。运算放大器、模数转换器、数字信号处理电路性能良好,满足传感器系统要求。

A sensor system was designed based on the standard CMOS process.The thermal vacuum sensor,operational amplifier（OPAMP）,successive approximation register analog to digital converter（SAR ADC） and digital signal processing circuit were integrated in it.The vacuum sensor worked in the constant-current mode whose gas pressure sensitive range extended from 1 Pa to 105 Pa.The OPAMP adopted the complementary differential pairs to obtain the rail to rail common-mode input range.The capacitor array of the DAC in the SAR ADC was optimized,and the offset voltage of the comparator was eliminated using the output offset storage technique.The digital circuit transformed voltage signal into gas pressure value by the look-up table.The results show that the OPAMP can drive 200 Ω resistors distortion lessly,and the ADC achieves a resolution of 9.5 bit.The OPAMP,SAR ADC and digital circuit have good performances,and meet the requirements of the sensor system.