Readout system for MEMS-based capacitive accelerometers and strain sensors, and method for reading

摘要

A method and an electronic readout circuit for measuring a capacitance of a MEMS sensor are disclosed. In one aspect, the readout circuit includes: an input stage for receiving a first signal from the sensor and for presenting a second signal; a charge amplifier stage for amplifying and integrating the second signal; and a control logic for controlling the readout circuit according to a predefined timing relation synchronized to actuation voltages applied to the sensor for generating the first signal. The readout circuit may further includes a first switching unit for applying a first reference voltage to the sensor and a second switching unit for applying the second signal to the charge amplifier stage, wherein the first and the second switching units are controlled according to the predefined timing relation such that a plurality of the second signals are accumulated.

主权项

1. An electronic readout-circuit for measuring a capacitance value of a microelectromechanical systems (MEMS) sensor and for generating an output signal indicative of the measured capacitance value, the readout-circuit comprising:
an input stage having an input port configured to receive a first signal from the MEMS sensor, the first signal being indicative of the capacitance value, and an output port configured to produce a second signal derived from the first signal; a charge amplifier stage configured to receive the second signal from the output port of the input stage, the charge amplifier stage having components for amplifying and integrating the second signal, and an output configured to send the amplified and integrated second signal as the output signal; a control logic configured to control the operation of the readout-circuit according to a predefined timing relation synchronized to a first and a second actuation voltage, the first and second actuation voltages being applied to the MEMS sensor for generating the first signal on an output of the MEMS sensor; a first switching unit connected between the input port of the input stage and a first reference voltage source and configured to apply a first reference voltage to the MEMS sensor; a second switching unit connected between the input port and the output port of the input stage and configured to apply the second signal to a first input of the charge amplifier stage, wherein the first and the second switching units are connected to the control logic for being controlled according to the predefined timing relation such that a plurality of the second signals are accumulated on the charge amplifier stage; an input capacitor connected between the MEMS sensor and the second switching unit and configured to capacitively couple the output of the MEMS sensor to the first input of the charge amplifier stage while creating a DC-offset between the sensor and the charge amplifier stage; a second reference voltage source connected to a second input of the charge amplifier stage; and a third switching unit connected between the input capacitor and the second reference voltage source and configured to pre-charge the input capacitor for creating the DC-offset.