Synaptics Incorporated
Active feedforward interference cancellation techniques for sensor analog front-end

Abstract:

Embodiments herein provide input devices that include a display panel on which a discrete capacitive sensor is disposed to form a capacitive sensing region. The capacitive sensor includes a plurality of sensor electrodes that are used to generate capacitive sensing signals indicating user interaction with the input device. Moreover, the input device includes analog interference detection circuitry for mitigating the negative impact of display noise on capacitive sensing. In one embodiment, the input device includes a reference circuit which is capacitively coupled to a display noise source and outputs a reference voltage that biases a charge integrator in a receiver channel used for capacitive sensing. In another embodiment, the input device includes a current conveyor coupled to an idle transmitter electrode of the sensor electrodes which outputs a correction current to a receiver channel to cancel a display noise current injected into the receiver channel.