弛张振荡器在高精度体温计芯片中的应用

Relaxation Oscillator Application for the High Accuracy Clinical Thermometer Chip

设计了一款基于弛张振荡器的温度测量电路,通过参考/感应振荡器电路,将热敏电阻的阻值变化转变成数字化的频率信号送系统处理。弛张振荡器使用了具有施密特触发器相同功能的RS触发器,降低了芯片对工艺的要求,便于在低电压和宽温度范围正常工作。该温度测量电路被成功地应用于一款便携式电子体温计芯片,芯片采用0.5μm 1.5 V DMSP CMOS工艺,面积为1 250μm×1 260μm,在1.1 V的低电压下测量精度高达0.05°C,工作电流为30μA,待机电流为0.2μA。

A relaxation oscillator based temperature measurement circuit has been presented in this paper. The reference/sensor frequency generation circuit is used to convert the change of thermistor sensor into frequency signal for digital processing. A RS trigger is designed which has the same function as Schmitt trigger for the relaxation oscillator. The advantage is that RS trigger reduces the dependence to the process and has better performance under low voltage and wide temperature range. This temperature measurement circuit is applied in a clinical thermometer chip, which can measure temperature with an accuracy of better than 0.05 ℃ down to 1.1 V battery voltage with the operation current of 30 μA and quiescent current of 0.2 μA. It has a die size of 1 250 μm× 1 260 μm and is fabricated in a 0. 5 μm 1.5 V double metal single poly CMOS process.