Current-Based Charge Compensation in a Touch Sensor
AssigneeAtmel Corporation
InventorCarl Olof Fredrik Jonsson
Life of this patent
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Abstract
In one embodiment, a method comprises generating a first current at a current source having a magnitude based on the magnitude of a second current flowing from a capacitive node of a touch sensor in the absence of a touch with respect to the capacitive node. The method further includes generating a third current from the capacitive node of the touch sensor in the presence of a touch with respect to the capacitive node. The first current and the third current are summed to cancel out at least a portion of the third current. The method further includes integrating, by an integrator, the sum of the first current and the third current to generate an output voltage.
Claims21
An apparatus comprising:
- a touch sensor controller operable to:
- apply a first voltage to a drive line of a touch sensor;
- transition the voltage applied to the drive line from the first voltage to a second voltage;
- sum a first current received from a sense line in response to the voltage transition applied to the drive line and a second current generated by a current source, the summing canceling out at least a portion of the first current;
- integrate, by an integrator, the sum of the first current and the second current to generate an output voltage;
- and
- determine, based on the output voltage, whether a touch has occurred with respect to a capacitive node coupled to the drive line and the sense line.
A method comprising:
- generating a first current from a current source, the first current having a magnitude based on the magnitude of a second current present at a capacitive node of a touch sensor in the absence of a touch with respect to the capacitive node;
- generating a third current at the capacitive node of the touch sensor in the presence of a touch with respect to the capacitive node;
- summing the first current and the third current to cancel out at least a portion of the third current;
- and
- integrating, by an integrator, the sum of the first charge and the third charge to generate an output voltage.
A circuit comprising:
- a current source configured to generate a first current having a magnitude based on the magnitude of a second current generated at a capacitive node of a touch sensor in the absence of a touch with respect to the capacitive node;
- a junction configured to sum the first current and a third current generated at the capacitive node of the touch sensor in the presence of a touch with respect to the capacitive node, the summation cancelling out at least a portion of the third charge;
- and
- an integrator configured to integrate the sum of the first current and the third current to generate an output voltage.
Dependencies are inferred from the claim text.