Design of micro-capacitance detection circuit for CMOS capacitive humidity sensor

In this paper, a micro-capacitance detection circuit based on 40nm CMOS process is designed for capacitive humidity sensor. The circuit can detect the small change of capacitance value when the environmental humidity changes. The main principle of the circuit is to convert the variation of capacitance into pulse width, and count the time of pulse width by counter to realize the digital output without using analog to digital converter, which is convenient for subsequent signal processing. The simulation results show that the power consumption is around 0.2mW and the conversion resolution is 4us/pF under 1.2V power supply. The presented humidity sensor has the advantages of high linear-ity, good precision and low power consumption.