Coded integration of a self-capacitance array
First Claim
1. A method for measuring a self-capacitance of a plurality of electrodes, the method comprising:
- coupling the plurality of electrodes to a sense channel during a plurality of integration periods, wherein at least two of the plurality of electrodes are simultaneously coupled to the sense channel during at least one of the plurality of integration periods;
generating a plurality of composite output signals, one or more of the plurality of composite output signals based on an output of the sense channel during a corresponding integration period; and
demodulating the plurality of composite output signals to extract a self-capacitance measurement for the plurality of electrodes.
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Abstract
Coded integration of a self-capacitance array to improve signal-to-noise ratio (SNR) of self-capacitance measurements is disclosed. A composite measurement of the self-capacitance of a plurality of electrodes can be measured for a plurality of integration periods. The composite measurements can include weighted contributions of charge from the plurality of electrodes, the weighting corresponding to a code. In some examples, the weighted contribution can include positive contributions integrated by a first integrator circuit and negative contributions integrated by a second integrator circuit. The composite measurements of the self-capacitance for the plurality of integration periods can be decoded to extract the self-capacitance measurement for the electrodes. The SNR for the self-capacitance measurements can therefore be improved by increasing the number of samples during the total integration period without requiring dedicated sensing circuitry for the electrodes.
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Citations
32 Claims
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1. A method for measuring a self-capacitance of a plurality of electrodes, the method comprising:
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coupling the plurality of electrodes to a sense channel during a plurality of integration periods, wherein at least two of the plurality of electrodes are simultaneously coupled to the sense channel during at least one of the plurality of integration periods; generating a plurality of composite output signals, one or more of the plurality of composite output signals based on an output of the sense channel during a corresponding integration period; and demodulating the plurality of composite output signals to extract a self-capacitance measurement for the plurality of electrodes. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. An apparatus for measuring self-capacitance, the apparatus comprising:
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sensing circuitry configured to be coupled to a plurality of electrodes via a plurality of switches; logic configurable to control the plurality of switches to couple the plurality of electrodes to the sensing circuitry, wherein the plurality of switches can be controlled to simultaneously couple the sensing circuitry to at least two of the plurality of electrodes; and a demodulation section configurable to decode a plurality of outputs of the sensing circuitry to determine the self-capacitance of the plurality of electrodes. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
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Specification