LOW POWER CAPACITIVE HUMIDITY SENSOR READOUT IC WITH ON-CHIP TEMPERATURE SENSOR AND FULL DIGITAL OUTPUT FOR USN APPLICATIONS

In this paper, a low power CMOS integrated capacitance-to-frequency converter with on-chip temperature sensor and fully digital output designed for humidity sensor interface is newly proposed, which is manufactured by using a standard 0.35um 2P/3M CMOS process. This ROIC(Readout IC) consists of on-chip PTAT temperature sensing circuit, low power temperature-to-frequency converter, low power C-F converter, digital compensation circuit, OTP memory, control logic and serial I/O circuits. Capacitance interfacing capability of the circuit is ultra-wide, up to 350pF, which is higher than previously reported works(1). At a clock speed of 1MHz, the average power dissipation is as low as about 150uW with one humidity measurement per one second, which is lower than ever reported works(2-3). And the minimum detectable capacitance is as low as about 4.5fF.