Wide-temperature range CMOS capacitance to digital convertor for MEMS pressure sensors

We present a complementary metal-oxide-semiconductor (CMOS) capacitance to digital converter (CDC) for capacitive Microelectromechanical Systems (MEMS) pressure sensors, that is functionally tested over a wide temperature range from −20 °C to 225 °C. The proposed circuit uses a sigma-delta technique to convert the input ratio between sensor and reference capacitors into a digital output. A constant-gm biasing technique is used to alleviate performance degradation at high temperatures. The circuit is implemented using the IBM 0.13 μm CMOS process technology which incorporates a 2.5 V power supply. The simulation results show that the circuit offers 0.03% accuracy between −55 °C and 225 °C. The circuit is tested with a commercial MEMS capacitive pressure sensor. Experimental results show that the circuit offers good temperature stability, resolution of 1.44fF, and accuracy of 2.4% between −20 °C and 225 °C.