Real-time isolation of self-test and linear acceleration signals
AssigneeInvenSense, Inc.
InventorsKevin Hughes, Giacomo Laghi, Vito Avantaggiati
Life of this patent
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Abstract
A MEMS accelerometer includes proof masses that move in-phase in response to a sensed linear acceleration. Self-test drive circuitry imparts an out-of-phase movement onto the proof masses. The motion of the proof masses in response to the linear acceleration and the self-test movement is sensed as a sense signal on common sense electrodes. Processing circuitry extracts from a linear acceleration signal corresponding to the in-phase movement due to linear acceleration and a self-test signal corresponding to the out-of-phase movement due to the self-test drive signal.
Claims21
A microelectromechanical (MEMS) accelerometer, comprising:
- a first proof mass;
- a second proof mass;
- one or more first electrodes located adjacent to the first proof mass to sense movement of the first proof mass along a first axis in response to a linear acceleration along the first axis during a self-test time period;
- one or more second electrodes located adjacent to the second proof mass to sense movement of the second proof mass along the first axis during the self-test time period, wherein the first proof mass and the second proof mass move in-phase along the first axis in response to the linear acceleration along the first axis;
- self-test drive circuitry coupled to the first proof mass and the second proof mass, wherein the self-test drive circuitry is configured to continuously cause the first proof mass and the second proof mass to move out-of-phase along the first axis during the self-test time period;
- and
- processing circuitry coupled to the one or more first electrodes and the one or more second electrodes, wherein the processing circuitry comprises a demultiplexer configured to receive a sense signal during the self-test time period and to extract from the sense signal a self-test signal corresponding to the out-of-phase movement of the proof masses during the self-test time period and a linear acceleration signal corresponding to the in-phase movement of the proof masses during the self-test time period.
A method of self-testing a microelectromechanical (MEMS) accelerometer, comprising:
- applying a self-test drive signal at a first polarity to a first proof mass;
- applying the self-test drive signal at a second polarity to a second proof mass, wherein the first polarity of the self-test drive signal is opposite to the second polarity of the self-test drive signal, further wherein, applying the first polarity of the self-test drive signal to the first proof mass and applying the second polarity of the self-test drive signal to the second proof mass continuously causes the first proof mass and the second proof mass to move out-of-phase along a first axis during a self-test time period;
- detecting a sense signal during the self-test time period comprising a linear acceleration signal and a self-test sense signal, wherein the linear acceleration signal corresponds to the first proof mass and the second proof mass moving in-phase during the self-test time period and a self-test sense signal corresponds to the first proof mass and the second proof mass moving out-of-phase during the self-test time period;
- and
- extracting the self-test sense signal and the linear acceleration signal from the sense signal during the self-test time period.
Dependencies are inferred from the claim text.