A low-power readout circuit design for capacitive microsensors

A new readout circuit for capacitive microsensors is presented. The circuit produces a pulse-width proportional to the amount of capacitance change. It consist of two main block including capacitive-to-voltage converter block which is based on a switched-capacitor circuit, which leads to reduction in chip area and its power consumption, and a voltage-to-pulse-width converter, which leads to improving its robustness against interference. Moreover, another advantage of this interface circuit compared to the existing solutions is its ratiometric sensing configuration and its adjustable noise performance. Experimental results were obtained by pairing the topology realized in a CMOS 0.35 mu m technology with a MEMS variable capacitive sensor developed in our lab where a pulse-width signal is produced proportionally to the displacement of the MEMS sensor.