US 2023/0128205 A1Published application

Mems accelerometer self-test using a variable excitation voltage and fixed timing

AssigneeSTMicroelectronics S.r.l.

InventorsMarco GARBARINO, Davy CHOI, Francesco RIZZINI, Yamu HU

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Abstract

A microelectromechanical system (MEMS) accelerometer sensor has a mobile mass and a sensing capacitor. To self-test the sensor, a test signal having a variably controlled excitation voltage and a fixed pulse width is applied to the sensing capacitor. The leading and trailing edges of the test signal are aligned to coincide with reset phases of a sensing circuit coupled to the sensing capacitor. The variably controlled excitation voltage of the test signal is configured to cause an electrostatic force which produces a desired physical displacement of the mobile mass. During a read phase of the sensing circuit, a variation in capacitance of sensing capacitor due to the actual physical displacement of the mobile mass is sensed for comparison to the desired physical displacement.

Claims18

Dependent claims

A method for self-testing an accelerometer system comprising a plurality of microelectromechanical system (MEMS) accelerometer sensors, a charge sensing circuit and a multiplexer configured to selectively couple sensing outputs of the MEMS accelerometer sensors to the charge sensing circuit in a cyclically repeating sensing period, wherein each sensing period includes a reset phase and a read phase, the method comprising:

coupling the sensing outputs of a first MEMS accelerometer sensor of said plurality of MEMS accelerometer sensors through the multiplexer to the charge sensing circuit during a first sensing period;
applying a self-test voltage to a second MEMS accelerometer sensor of said plurality of MEMS accelerometer sensors during said first sensing period, said self-test voltage having a leading edge coinciding with the reset phase of said first sensing period, and wherein said self-test voltage has a variably controlled excitation voltage;
coupling the sensing outputs of the second MEMS accelerometer sensor through the multiplexer to the charge sensing circuit during a second sensing period that occurs subsequent to the first sensing period;
and
wherein said self-test voltage further has a trailing edge coinciding with the reset phase of said second sensing period.

2 more elements

A method for self-testing an accelerometer system comprising first, second and third microelectromechanical system (MEMS) accelerometer sensors, a charge sensing circuit and a multiplexer configured to selectively couple sensing outputs of the first, second and third MEMS accelerometer sensors to the charge sensing circuit in a cyclically repeating sensing period, wherein each sensing period includes a reset phase and a read phase, the method comprising:

coupling the sensing outputs of the first MEMS accelerometer sensor through the multiplexer to the charge sensing circuit during a first sensing period;
coupling the sensing outputs of the second MEMS accelerometer sensor through the multiplexer to the charge sensing circuit during a second sensing period;
coupling the sensing outputs of the third MEMS accelerometer sensor through the multiplexer to the charge sensing circuit during a third sensing period;
applying a first self-test voltage to the first MEMS accelerometer sensor during said second and third sensing periods, wherein said first self-test voltage has a first variably controlled excitation voltage with a leading edge coinciding with the reset phase of said second sensing period and a trailing edge coinciding with the reset phase of said first sensing period;
applying a second self-test voltage to the second MEMS accelerometer sensor during said third and first sensing periods, wherein said second self-test voltage has a second variably controlled excitation voltage with a leading edge coinciding with the reset phase of said third sensing period and a trailing edge coinciding with the reset phase of said second sensing period;
and
applying a third self-test voltage to the third MEMS accelerometer sensor during said first and second sensing periods, wherein said third self-test voltage has a third variably controlled excitation voltage with a leading edge coinciding with the reset phase of said first sensing period and a trailing edge coinciding with the reset phase of said third sensing period.

4 more elements

Dependencies are inferred from the claim text.