# US 9,436,337 B2 · Switched capacitance techniques for input sensing > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,436,337 B2 - Document ID: US9436337B2 - Status: Granted - Kind: B2 - Application number: 14/571,073 - Filed: 2014-12-15 - Published: 2016-06-16 - Granted: 2016-09-06 - Earliest claimed: 2014-12-15 - Assignees: Synaptics Incorporated - Applicants: Synaptics Incorporated - Inventors: Tracy Scott Dattalo - Web page: https://patentgrep.com/patent/US9436337B2 ## CPC - G06F 3/0446: {using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes} - G01D 5/24: by varying capacitance - G06F 3/0443: {using a single layer of sensing electrodes} - G06F 3/0445: {using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer} - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) - G01D: MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR ## Abstract Examples of the present disclosure generally relate to a switched capacitance technique for input sensing with an input device. A processing system includes an operational amplifier having a non-inverting input, an inverting input, and an output. The processing system further includes a first capacitor coupled between the output and the inverting input to form a feedback path, and a second capacitor. The processing system further includes a first switch coupled to the second capacitor. The first switch has a first state and a second state, where the first state couples the second capacitor to the first capacitor, and the second state couples the second capacitor to a measurement circuit. The processing system further includes a determination module coupled to the measurement circuit and configured to determine a capacitance measurement at the inverting input based on an amount of charge received by the second capacitor. ## Claims ### Claim 1 A processing system, comprising: an operational amplifier having a non-inverting input, an inverting input, and an output; a first capacitor coupled between the output and the inverting input to form a feedback path; a second capacitor; a first switch coupled to the second capacitor, the first switch having a first state and a second state, wherein the first state couples the second capacitor to the first capacitor, and the second state couples the second capacitor to a measurement circuit; and a determination module coupled to the measurement circuit and configured to determine a capacitance measurement at the inverting input based on an amount of charge received by the second capacitor. ### Claim 2 (depends on 1) The processing system of claim 1, wherein, when the first switch is in the first state, the first capacitor is connected in parallel with the second capacitor relative to the output and the inverting input. ### Claim 3 (depends on 1) The processing system of claim 1, wherein the first switch comprises a double pole, double throw (DPDT) switch, wherein a first pole of the DPDT switch is coupled to a first side of the second capacitor, and a second pole of the DPDT switch is coupled to a second side of the second capacitor. ### Claim 4 (depends on 1) The processing system of claim 1, wherein the measurement circuit comprises at least one integrator and at least one comparator. ### Claim 5 (depends on 1) The processing system of claim 1, wherein the measurement circuit comprises a sigma-delta modulation circuit. ### Claim 6 (depends on 1) The processing system of claim 1, further comprising a voltage source operable to drive a voltage onto the non-inverting input to cause the operational amplifier to drive an input sensing signal onto a sensor electrode. ### Claim 7 (depends on 6) The processing system of claim 6, wherein the capacitance measurement comprises a capacitance between the sensor electrode and an input object. ### Claim 8 (depends on 6) The processing system of claim 6, wherein the capacitance measurement comprises a capacitance between the sensor electrode and a receiver electrode. ### Claim 9 (depends on 1) The processing system of claim 1, further comprising a voltage source operable to drive a substantially constant input voltage onto the non-inverting input during a mutual capacitance sensing time period. ### Claim 10 (depends on 1) The processing system of claim 1, further comprising: a third capacitor; a second switch coupled to the third capacitor, the second switch having a third state and a fourth state, wherein the third state couples the third capacitor to the first capacitor, and the second state decouples the third capacitor from the first capacitor. ### Claim 11 (depends on 10) The processing system of claim 10, wherein the second switch is configured to switch between the third state and the fourth state based on an amount of charge received by the first capacitor. ### Claim 12 An input device for capacitive sensing, comprising: a plurality of sensor electrodes; and a processing system coupled to the plurality of sensor electrodes, the processing system comprising: an operational amplifier having a non-inverting input, an inverting input, and an output, wherein a sensor electrode included in the plurality of sensor electrodes is coupled to the inverting input; a voltage source coupled to the non-inverting input; a first capacitor coupled between the output and the inverting input to form a feedback path; a second capacitor; a first switch coupled to the second capacitor, the first switch having a first state and a second state, wherein the first state couples the second capacitor to the first capacitor, and the second state couples the second capacitor to a measurement circuit; and a determination module coupled to the measurement circuit and configured to determine a capacitance measurement of the sensor electrode based on an amount of charge received by the second capacitor. ### Claim 13 (depends on 12) The input device of claim 12, wherein, when the first switch is in the first state, the first capacitor is connected in parallel with the second capacitor relative to the output and the inverting input. ### Claim 14 (depends on 12) The input device of claim 12, wherein the first switch comprises a double pole, double throw (DPDT) switch, wherein a first pole of the DPDT switch is coupled to a first side of the second capacitor, and a second pole of the DPDT switch is coupled to a second side of the second capacitor. ### Claim 15 (depends on 12) The input device of claim 12, wherein the measurement circuit comprises at least one integrator and at least one comparator. ### Claim 16 (depends on 12) The input device of claim 12, wherein the measurement circuit comprises a sigma-delta modulation circuit. ### Claim 17 (depends on 12) The input device of claim 12, further comprising: a third capacitor; a second switch coupled to the third capacitor, the second switch having a third state and a fourth state, wherein the third state couples the third capacitor to the first capacitor, and the second state decouples the third capacitor from the first capacitor. ### Claim 18 (depends on 17) The input device of claim 17, wherein the second switch is configured to switch between the third state and the fourth state based on an amount of charge received by the first capacitor. ### Claim 19 A method of input sensing with a sensor electrode, the method comprising: driving an input voltage onto a non-inverting input of an operational amplifier, wherein a first capacitor is coupled between an output of the operational amplifier and an inverting input of the operational amplifier to form a feedback path; switching a second capacitor between a first state and a second state, wherein the first state couples the second capacitor to the first capacitor, and the second state couples the second capacitor to a measurement circuit; and determining a capacitance measurement associated with a sensor electrode coupled to the inverting input based on an amount of charge received by the second capacitor. ### Claim 20 (depends on 19) The method of claim 19, further comprising driving a voltage onto the non-inverting input to cause the operational amplifier to drive an input sensing signal onto the sensor electrode. ### Claim 21 (depends on 19) The method of claim 19, wherein the capacitance measurement comprises a capacitance between the sensor electrode and an input object. ### Claim 22 (depends on 19) The method of claim 19, wherein the capacitance measurement comprises a capacitance between the sensor electrode and a receiver electrode. ### Claim 23 (depends on 19) The method of claim 19, further comprising driving a substantially constant input voltage onto the non-inverting input during a mutual capacitance sensing time period. ### Claim 24 (depends on 19) The method of claim 19, further comprising switching a third capacitor between a third state and a fourth state based on an amount of charge received by the first capacitor, wherein the third state couples the third capacitor to the first capacitor, and the second state decouples the third capacitor from the first capacitor.