Capacitance to code converter with sigma-delta modulator

An apparatus, comprising:

• a matrix-scanning device comprising a plurality of drive lines and a plurality of sense lines and a sense element is located at an intersection of one of the plurality of drive lines and one of the plurality of sense lines;
• a modulation circuit selectively coupled to the plurality of drive lines and the plurality of sense lines;
• and
• a switching circuit having a first plurality of switches and a second plurality of switches controlled in response to a clock, wherein the modulation circuit is configured to measure a mutual capacitance on the sense element using the first plurality of switches, wherein the modulation circuit is configured to convert the measured mutual capacitance to a first digital value, wherein the modulation circuit is configured to measure a self-capacitance on at least one of the plurality of drive lines using the second plurality of switches, and wherein the modulation circuit is configured to convert the self-capacitance to a second digital value.

A system, comprising:

• a matrix-scanning device comprising a plurality of sense elements, wherein the plurality of sense elements are intersections between a plurality of drive lines and a plurality of sense lines of the matrix-scanning device;
• a processing device coupled to the matrix-scanning device, the processing device comprising:
• a switching circuit having a first plurality of switches and a second plurality of switches, wherein the processing device is configured to control the first and second plurality of switches using a clock;
• and
• a modulation circuit configured to be coupled to the plurality of drive lines and the plurality of sense lines, wherein the modulation circuit is configured to measure a mutual capacitance on the one sense element using the first plurality of switches, wherein the modulation circuit is configured to convert the measured mutual capacitance to a first digital value, wherein the modulation circuit is configured to measure a self-capacitance on at least one of the plurality of drive line using the second plurality of switches, and wherein the modulation circuit is configured to convert the measured self-capacitance to a second digital value.