A Low Power Capacitance to Frequency Converter in 180nm CMOS for an Implantable Capacitive Pressure Sensor

Abstract

We present a capacitance to frequency converter (CFC) implemented in 180nm CMOS technology intended for pressure monitoring in the body. It is designed to sense pressure changes from 300mmHg to 1000mHg (capacitance range from 6pF to 7 pF) corresponding to a frequency output range of 1.8MHz to 13.4MHz. The frequency output is modulated with a 1.63KHz clock and the number of cycles per period is counted. This readout circuit has a resolution of 0.28fF (0.196mmHg) with a power consumption of 72µW at 1.8 V supply.