Stmicroelectronics S.r.l.

Stmicroelectronics Gmbh

Anthony Junior Casillan

Yamu Hu

Naren K Sahoo

David C McClure

Alessandro Gasparini

Alessandro Tocchio

Tom Youssef

A microelectromechanical system (MEMS) accelerometer sensor has a mobile mass and a sensing capacitor. To self-test the sensor, a test signal is applied to the sensing capacitor during a reset phase of a sensing circuit coupled to the sensing capacitor. The test signal is configured to cause an electrostatic force which produces a physical displacement of the mobile mass corresponding to a desired acceleration value. Then, during a read phase of the sensing circuit, a variation in capacitance of sensing capacitor due to the physical displacement of the mobile mass is sensed. This sensed variation in capacitance is converted to a sensed acceleration value. A comparison of the sensed acceleration value to the desired acceleration value provides an indication of an error in operation of the MEMS accelerometer sensor if the sensed acceleration value and desired acceleration value are not substantially equal.

MEMS accelerometer self-test using an active mobile mass deflection technique

A modulated digital input signal is passed through a conditioning circuit to generate a first input signal. An error amplifier circuit receives the first input signal and a second input signal, and controls the operation of a MOS transistor to generate an output signal that is current modulated. The output signal is sensed to generate a feedback signal. A switching circuit selectively applies the feedback signal as the second input signal in response to a transition of the modulated digital input signal from a first logic state to a second logic state. The switching circuit alternatively selectively applies a fixed reference signal as the second input signal to the error amplifier in response to a transition of the modulated digital input signal from the second logic state to the first logic state.

Current modulation circuit

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Lewisville, TX, United States of America

Anthony Junior Casillan