Capacitive microelectromechanical sensor with self-test capability
AssigneeMurata Manufacturing Co., Ltd.
InventorsLasse AALTONEN, Jouni ERKKILÄ
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Abstract
A capacitive sensor that includes at least one capacitive element and a switched-capacitor readout circuit part for detecting at least one signal capacitance that results from motions of the capacitive element. The self-test bias voltage of the actuation circuit part is coupled to the capacitive element during a first period that is synchronized to the front end reset period and occurs when the self-test of the capacitive sensor is enabled by the self-test controller.
Claims20
A capacitive sensor, comprising:
- at least one capacitive element;
- a switched-capacitor readout circuit configured to detect at least one signal capacitance that results from motions of the capacitive element;
- a first switch arrangement configured to electrically couple the switched-capacitor readout circuit part to the capacitive element for a front end readout period, and to electrically decouple the switched-capacitor readout circuit part from the capacitive element for a front end reset period;
- a self-test controller configured to enable and disable a self-test of the capacitive sensor;
- an actuation circuit configured to generate a self-test bias voltage for electrostatic deflection of the capacitive element;
- a second switch arrangement configured to electrically couple the self-test bias voltage of the actuation circuit part to the capacitive element during a first period, wherein the first period is synchronized to the front end reset period and is configured to occur when the self-test of the capacitive sensor is enabled by the self-test controller, and to electrically decouple the actuation circuit part from the capacitive element in times other than the first period,
- wherein the actuation circuit includes a high-voltage charge pump and a high-voltage charge pump control circuitry configured to enable and disable generation of the self-test bias voltage by the high-voltage charge pump,
- wherein the second switch arrangement is configured to generate a self-test control signal, a first state of the self-test control signal relating to the first period, and the second state of the self-test control signal relating to the times other than the first period, and
- wherein the high-voltage charge pump control circuitry is responsive to the self-test control signal such that enabling and disabling generation of the self-test bias voltage by the high-voltage charge pump depends on the self-test control signal.
A self-test method for a capacitive sensor that includes at least one capacitive element, a switched-capacitor readout circuit part for detecting at least one signal capacitance that results from motions of the capacitive element, and a first switch arrangement configured to electrically couple the switched-capacitor readout circuit part to the capacitive element for a front end readout period, and to electrically decouple the switched-capacitor readout circuit part from the capacitive element for a front end reset period, the method comprising:
- generating in the capacitive sensor a self-test bias voltage for electrostatic deflection of the capacitive element during first periods, wherein the first periods are synchronized to the front end reset periods and are configured to occur when the self-test of the capacitive sensor is enabled;
- electrically decoupling the self-test bias voltage from the capacitive element in times other than the first period;
- generating a self-test control signal, wherein a first state of the self-test control signal relates to the first period, and the second state of the self-test control signal relates to the times other than the first period;
- and
- enabling and disabling generation of the self-test bias voltage by the high-voltage charge pump in response to the self-test control signal.
Dependencies are inferred from the claim text.