Constant charge or capacitance for capacitive micro-electrical-mechanical system sensors

Abstract

Embodiments for constant charge or capacitance for capacitive micro-electro-mechanical system (MEMS) sensors are presented herein. A MEMS device comprises a sense element circuit comprising a bias resistance, a charge-pump, and a capacitive sense element comprising an electrode and a sense capacitance. The charge-pump generates, at a bias resistor electrically coupled to the electrode, a bias voltage that is inversely proportional to a capacitance value comprising a value of the sense capacitance to facilitate maintenance of a nominally constant charge on the electrode. A sensing circuit comprises an alternating current (AC) signal source that generates an AC signal at a defined frequency; and generates, based on the AC signal, an AC test voltage at a test capacitance that is electrically coupled to the electrode. The sense element circuit generates, based on the AC test voltage at the defined frequency, an output signal representing the value of the sense capacitance.