Method and circuit for detecting displacements using micro-electromechanical sensors with compensation of parasitic capacitances and spurious displacements

A circuit for detecting displacements using a micro-electromechanical sensor which comprises a fixed body and a mobile mass that form a first sensing capacitor and a second sensing capacitor, which are connected to a first input terminal and, respectively, to a first output terminal and to a second output terminal and have, at rest, a common sensing capacitance and have, during displacement, a capacitive unbalancing;

• the circuit comprising:
• a first negative-feedback loop, which can be closed selectively and comprises said first and second sensing capacitors and first amplifier means;
• and
• voltage-source means connected to said first amplifier means via capacitive driving means and supplying a staircase sensing voltage when said first negative-feedback loop is closed, so as to produce variations of an electrical driving quantity of said sensor, which are inversely proportional to said common sensing capacitance.

A device, comprising:

• a microelectromechanical sensor including first and second sensing capacitors having respective first terminals coupled to a sensing input and respective second terminals coupled to first and second sensing outputs, respectively, the sensor being configured such that the sensing capacitors have a common capacitance when the sensor is at rest and an unbalanced capacitance when the sensor is displaced;
• a staircase voltage generator;
• first and second driving capacitors;
• and
• a compensation amplifier having first and second compensation inputs and a compensation output selectively connected, in a first feedback configuration, with the compensation output coupled to the sensing input and the first and second compensation inputs coupled to the first and second sensing outputs, and, in a second feedback configuration, with the first and second compensation inputs coupled, via the first and second driving capacitors, respectively, to the staircase voltage generator.