Ohmmeter for sensor electrodes
AssigneeSynaptics Incorporated
InventorsEric Scott BOHANNON, Steve Chikin LO, Petr SHEPELEV
Life of this patent
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Abstract
An input device includes a plurality of sensor electrodes and a processing system that is operable in at least a first mode or a second mode. The processing system is configured to receive an input current from a pair of the sensor electrodes. When operating the first mode, the processing system is configured to measure a capacitance across the pair of sensor electrodes based on the received input current. When operating the second mode, the processing system is configured to measure a resistance between the pair of sensor electrodes based on the received input current.
Claims20
An input device, comprising:
- a plurality of sensor electrodes disposed within a sensing region of the input device;
- and
- a processing system coupled to at least a pair of the sensor electrodes and configured to operate in at least a first mode or a second mode, wherein:
- when operating in the first mode, the processing system is configured to:
- measure a first current across the pair of sensor electrodes;
- and
- determine a capacitance of the pair of sensor electrodes based on the measured first current;
- and
- when operating in the second mode, the processing system is configured to:
- measure a second current across the pair of sensor electrodes;
- and
- determine a resistance of the pair of sensor electrodes based on the measured second current.
A method of operating an input device, comprising:
- receiving a control signal indicating an operating mode of the input device, wherein the input device is configurable in at least a first mode or a second mode;
- determining a capacitance of a pair of sensor electrodes disposed within a sensing region of the input device when the control signal indicates the first mode of operation, wherein the capacitance is determined by:
- measuring a first current across the pair of sensor electrodes;
- and
- determining the capacitance of the pair of sensor electrodes based on the measured first current;
- and
- determining a resistance of the pair of sensor electrodes when the control signal indicates the second mode of operation, wherein the resistance is determined by:
- measuring a second current across the pair of sensor electrodes;
- and
- determining the resistance of the pair of sensor electrodes based on the measured second current.
An analog front end (AFE) for an input device operable in at least a first mode or a second, the AFE comprising:
- an amplifier configured to amplify an input current received from a pair of sensor electrodes;
- a demodulator configured to selectively demodulate the amplified input current based at least in part on the operating mode of the input device;
- and
- an analog-to-digital converter (ADC) configured to convert the amplified input current to:
- an alternating current (AC) value indicating a capacitance of the pair of sensor electrodes when the input device is configured to operate in the first mode;
- and
- a direct current (DC) value indicating a resistance of the pair of sensor electrodes when the input device is configured to operate in the second mode.
Dependencies are inferred from the claim text.