CODED INTEGRATION OF A SELF-CAPACITANCE ARRAY

摘要

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.

主权项

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.