Non-linear feedback capacitance sensing

摘要

A processing system for an input device includes a comparator, a digital-to-analog converter (DAC), and a feedback path coupling the DAC to the comparator. The comparator generates a first comparison signal associated with a resulting signal and a first output signal of the DAC; and generates a second comparison signal associated with the resulting signal and a second output signal of the DAC. The processing system also includes a control module and a determination module. The control module is coupled to the DAC and to the comparator's output and modifies a rising reference value and a falling reference value based on the first comparison signal and the second comparison signal, respectively. The determination module determines positional information for an input object in a sensing region of the input device based on the rising reference value and the falling reference value.

主权项

1. A processing system for an input device, the processing system comprising:
a transmitter module configured to drive a transmitter signal onto a transmitter electrode,
wherein the transmitter signal comprises a plurality of sensing cycles, andwherein each sensing cycle of the plurality of sensing cycles comprises a rising portion and a falling portion; a receiver module configured to receive a resulting signal with a receiver electrode, the receiver module comprising:
a digital-to-analog converter (DAC);a comparator configured to:
generate, for a rising portion of a sensing cycle of the plurality of sensing signals, a first comparison signal associated with the resulting signal and a first output signal of the DAC; andgenerate, for a falling portion of the sensing cycle, a second comparison signal associated with the resulting signal and a second output signal of the DAC;a feedback path operatively coupling the DAC to the comparator and configured to maintain an input node of the comparator at an approximately constant value; anda control module operatively coupled to the DAC and to an output of the comparator and configured to modify a rising reference value based on the first comparison signal and a falling reference value based on the second comparison signal; and a determination module configured to determine positional information for an input object in a sensing region of the input device based on the rising reference value and the falling reference value.