Capacitance to code converter with sigma-delta modulator
First Claim
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1. A method, comprising:
- measuring a mutual capacitance on a sense element of a sensing device using a modulation circuit, wherein the sensing device comprises a plurality of drive lines and a plurality of sense lines, and wherein the sense element comprises an intersection between one drive line of the plurality of drive lines and one sense line of the plurality of sense lines, and wherein the sense element is representative of a capacitor, and wherein the measuring the mutual capacitance on the sense element comprises;
applying a drive signal to the one drive line using an excitation signal source; and
sensing, by the modulation circuit, the drive signal on the one sense line to measure the mutual capacitance of the capacitor;
switching the capacitor to be coupled and decoupled to a modulator capacitor of the modulation circuit using a plurality of switches, wherein the plurality of switches is controlled by a spread spectrum clock; and
converting the mutual capacitance measured on the sense element to a digital value.
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Abstract
An apparatus and method of converting a capacitance measured on a sensor element to a digital value. The apparatus may include a switching capacitor as a sensor element, a modulation circuit coupled to the sensor element, and a switching circuit having a plurality of switches controlled by a variable-period clock. The modulation circuit is configured to measure a capacitance on the sense element and to convert the measured capacitance to a digital value.
539 Citations
20 Claims
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1. A method, comprising:
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measuring a mutual capacitance on a sense element of a sensing device using a modulation circuit, wherein the sensing device comprises a plurality of drive lines and a plurality of sense lines, and wherein the sense element comprises an intersection between one drive line of the plurality of drive lines and one sense line of the plurality of sense lines, and wherein the sense element is representative of a capacitor, and wherein the measuring the mutual capacitance on the sense element comprises; applying a drive signal to the one drive line using an excitation signal source; and sensing, by the modulation circuit, the drive signal on the one sense line to measure the mutual capacitance of the capacitor; switching the capacitor to be coupled and decoupled to a modulator capacitor of the modulation circuit using a plurality of switches, wherein the plurality of switches is controlled by a spread spectrum clock; and converting the mutual capacitance measured on the sense element to a digital value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An apparatus comprising:
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a sensing device comprising a plurality of drive lines and a plurality of sense lines to form a plurality of sense elements, wherein the plurality of sense elements comprises intersections between the plurality of drive lines and the plurality of sense lines, wherein the plurality of sense elements is represented as capacitors; an excitation signal source to provide a drive signal; a modulation circuit to be selectively coupled to one or more of the plurality of sense elements; and a switching circuit having a plurality of switches controlled by a variable-period clock, wherein the modulation circuit is to measure mutual capacitances of the plurality of sense elements using the plurality of switches, and wherein the modulation circuit is to convert the measured mutual capacitances to digital values, wherein the modulation circuit is to measure one or more of the mutual capacitances of the one or more of one of the plurality of sense elements by applying the drive signal to a respective one of the plurality of drive lines and sensing the drive signal on a corresponding one of the plurality of sense lines. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17)
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18. A system comprising:
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a capacitance sense array comprising a plurality of sense elements, wherein each of the plurality of sense elements comprises intersections between a plurality of drive lines and a plurality of sense lines, wherein the plurality of sense elements is representative of switching capacitors; and a processing device coupled to the capacitance sense array, the processing device comprising; an excitation signal source to provide a drive signal; a switching circuit having a plurality of switches, wherein the processing device is to control the plurality of switches using a variable-period clock; and a modulation circuit to be coupled to one of the plurality of sense elements, wherein the modulation circuit is to measure a mutual capacitance on the one of the plurality of sense elements using the plurality of switches, and wherein the modulation circuit is to convert the measured mutual capacitance to a digital value. - View Dependent Claims (19, 20)
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Specification