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US 12,498,392 B2Granted
Dual axis accelerometer with compensation electrodes
AssigneeInvenSense, Inc.
InventorsRoberto Martini, Luca Coronato, Xian Huang
Life of this patent
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Abstract
A dual axis accelerometer with a single proof mass measures in-plane acceleration (e.g., either along an x-axis or a y-axis), out-of-plane acceleration (e.g., normal to an x-y plane), and tilt of a fixed portion of a MEMS layer (e.g., normal to the x-y plane). In response to a tilt measurement, the dual-axis accelerometer compensates any offset (e.g., variability) of the out-of-plane accelerometer in order to maintain offset stability. In some embodiments, multiple dual axis accelerometers, perpendicularly configured, may be implemented via processing circuitry to offer three axis sensitivity capability.
Claims23
A multi-axis microelectromechanical system (MEMS) accelerometer, comprising:
- one or more anchors;
- a MEMS structure within a MEMS layer, comprising at least one proof mass coupled to the one or more anchors via one or more springs, the at least one proof mass configured to move out-of-plane in response to an out-of-plane force and to move in-plane in response to an in-plane force;
- one or more out-of-plane sense electrodes configured to measure the out-of-plane force based on the out-of-plane movement of the at least one proof mass;
- one or more in-plane sense electrodes configured to measure the in-plane force based on the in-plane movement of the at least one proof mass;
- one or more tilt sense electrodes configured to measure a tilt of a fixed portion of the MEMS layer;
- and
- a first signal and a second signal, wherein the first signal is applied to the at least one proof mass to produce one or more first sense signals with respect to the one or more in-plane sense electrodes and one or more second sense signals with respect to the one or more out- of-plane sense electrodes, and wherein the second signal is applied to the one or more tilt sense electrodes to produce one or more third sense signals with respect to the fixed portion of the MEMS layer.
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A multi-axis microelectromechanical system (MEMS) accelerometer, comprising:
- a first MEMS accelerometer, comprising:
- a first MEMS structure in a first MEMS layer including a first proof mass configured to translate in-plane in response to a first in-plane force and to move out-of-plane in response to an out-of-plane force perpendicular to the first in-plane force;
- a first fixed portion within the first MEMS layer, wherein one or more first in-plane electrodes are located adjacent to the first proof mass to form a first capacitance that changes with the in-plane translation of the first proof mass;
- a first out-of-plane electrode located below the first proof mass to form a second capacitance that changes with the out-of-plane movement of the first proof mass;
- and
- a tilt electrode located below the first fixed portion to form a third capacitor with the first fixed portion that has a third capacitance that is based on a tilt of the first fixed portion;
- and
- processing circuitry configured to apply a first signal to the first proof mass to generate a first sense signal based on the first capacitance and a second sense signal based on the second capacitance, to apply a second signal to the tilt electrode to generate a third sense signal based on the third capacitance, to determine a first in-plane acceleration based on the first sense signal, to determine an out-of-plane acceleration based on the second sense signal, and to determine the tilt of the first fixed portion within the first MEMS layer based on the third sense signal.
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A method, comprising:
- receiving a first signal from a multi-axis MEMS accelerometer, wherein the first signal is based on an in-plane movement between a proof mass in a MEMS layer and at least one fixed electrode of a fixed portion of the MEMS layer, and wherein the first signal has a first frequency;
- receiving a second signal from the multi-axis MEMS accelerometer, wherein the second signal is based on an out-of-plane movement between the proof mass and at least one out-of-plane sense electrode, and wherein the second signal has the first frequency;
- receiving a third signal from the multi-axis MEMS accelerometer, wherein the third signal is based on an out-of-plane tilt of the fixed portion of the MEMS layer and at least one tilt electrode, wherein the third signal has a second frequency, and wherein the third signal is received as a combined signal with one of the first signal or the second signal;
- demultiplexing, from the combined signal based on the first frequency and the second frequency, the third signal and the one of the first signal or the second signal within the combined signal;
- determining an in-plane acceleration based on the first signal;
- determining an out-of-plane acceleration based on the second signal;
- and determining a tilt based on the third signal.
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Dependencies are inferred from the claim text.