Active matrix capacitive sensor for common-mode cancellation
First Claim
1. A processing system for performing capacitive sensing, the processing system comprising:
- selection logic configured to apply, during a first time period, a charging voltage to a first sensor electrode and a second sensor electrode, wherein the second sensor electrode neighbors the first sensor electrode in a sensor electrode matrix, wherein the sensor electrode matrix comprises a plurality of sensor electrodes forming rows and columns on a common plane, wherein the plurality of sensor electrodes comprises the first and second sensor electrodes; and
a sensor circuit configured to measure, during a second time period, a first charge stored on the first sensor electrode resulting from applying the charging voltage, wherein the selection logic is configured to bias the second sensor electrode to a reference voltage during the second time period.
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Abstract
This disclosure generally provides an input device that includes a plurality of sensor modules coupled to sensor electrodes arranged in a matrix that measure capacitive sensing signals corresponding to the electrodes. To mitigate the effect of capacitive coupling between a sensor electrode being sensed and its neighbors in the matrix, the input device drives the neighboring electrodes in a same manner as the selected sensor electrode so that there is little or no voltage difference between the sensor electrode being sensed and its neighbors. For example, during a drive phase, the electrode being sensed and the neighboring electrodes are coupled to the same charge voltage. During a read phase, the neighboring electrodes and the selected electrode may be coupled to the same reference voltage—e.g., ground—so there is again no voltage difference between the electrodes.
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Citations
21 Claims
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1. A processing system for performing capacitive sensing, the processing system comprising:
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selection logic configured to apply, during a first time period, a charging voltage to a first sensor electrode and a second sensor electrode, wherein the second sensor electrode neighbors the first sensor electrode in a sensor electrode matrix, wherein the sensor electrode matrix comprises a plurality of sensor electrodes forming rows and columns on a common plane, wherein the plurality of sensor electrodes comprises the first and second sensor electrodes; and a sensor circuit configured to measure, during a second time period, a first charge stored on the first sensor electrode resulting from applying the charging voltage, wherein the selection logic is configured to bias the second sensor electrode to a reference voltage during the second time period. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An input device, comprising:
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a plurality of sensor electrodes arranged in a matrix comprising a plurality of sensor electrodes forming rows and columns on a common plane; a processing system configured to; apply, during a first time period, a charging voltage to a first sensor electrode of the plurality of sensor electrodes and a second sensor electrode of the plurality of sensor electrodes, wherein the second sensor electrode neighbors the first sensor electrode in the matrix, measure, during a second time period, a first charge stored on the first sensor electrode resulting from applying the charging voltage, and bias the second sensor electrode to a reference voltage during the second time period. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. A method for performing capacitive sensing, the method comprising:
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applying, during a first time period, a charging voltage to a first sensor electrode and to a second sensor electrode neighboring the first sensor electrode in a sensor electrode matrix, wherein the sensor electrode matrix comprises a plurality of sensor electrodes forming rows and columns on a common plane, wherein the plurality of sensor electrodes comprises the first and second sensor electrodes; measuring, during a second time period, a first charge stored on the first sensor electrode resulting from applying the charging voltage; and biasing the second sensor electrode to a reference voltage during the second time period. - View Dependent Claims (18, 19, 20)
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21. An input device, comprising:
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a plurality of sensor electrodes arranged in a matrix; first and second row select lines selectively coupling first and second sensor electrodes in the matrix to a first data line; and a processing system configured to; apply, during a first time period, a charging voltage to the first sensor electrode using the first data line, apply, during the first time period, the charging voltage to a third sensor electrode in the matrix using a second data line; and measure, during a second time period, a charge stored on the first sensor electrode resulting from applying the charging voltage using the first data line, wherein the second sensor electrode and third sensor electrode are electrically floating during the second time period.
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Specification