A 3.3V 15.6b 6.1pJ/0.02% RH with 10ms Response Humidity Sensor for Respiratory Monitoring

Abstract

An event-driven and energy-efficient humidity sensor for environment detection and healthcare monitoring is presented. A differential CMOS-MEMS humidity device and proportion-based capacitance-to-digit readout circuit are proposed to overcome PVT variations, and in the meantime to improve sensitivity, response time, and conversion energy. This chip achieves 15.6b 20-90 % RH at 1KS/s, 6.1pJ per 0.02% RH of sensitivity, and 10ms fast response time in TSMC 0.35-mu m CMOS MEMS process. With variations in temperature and voltage, our proposal can minimize the errors from 40% RH to 0.2% RH and 50% RH to 0.1% RH, making it very suitable for wearable respiratory monitoring.