Charge compensation for capacitive touch sensor nodes

摘要

In one embodiment, a method comprises generating a first charge at a capacitor system having a magnitude based on the magnitude of a second charge present at 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 charge at the capacitive node of the touch sensor in the presence of a touch with respect to the capacitive node. The first charge and the third charge are summed to cancel out at least a portion of the third charge. The method further includes integrating, by an integrator, the sum of the first charge and the third charge to generate an output voltage.

主权项

1. An apparatus comprising:
a touch-sensor controller operable to:
apply a first voltage to a drive line of a touch sensor;apply a second voltage to an electrode of a capacitor system;transition the voltage applied to the drive line from the first voltage to the second voltage and the voltage applied to the electrode of the capacitor system from the second voltage to the first voltage;sum a first charge received from a sense line in response to the voltage transition applied to the drive line and a second charge received from the capacitor system in response to the voltage transition applied to the electrode of the capacitor system, the summing canceling out at least a portion of the first charge;integrate, by an integrator, the sum of the first charge and the second charge to generate an output voltage; andconvert the output voltage to a digital value and use the digital value to determine whether a touch has occurred with respect to a capacitive node coupled to the drive line and the sense line.