US Patent 9013444 Self-capacitance measurement with isolated capacitance

In one embodiment, a method includes dividing a first amount of charge between a capacitance of a touch sensor and a compensation capacitor. The division of the first amount of charge results in a first voltage at an input node. The method also includes isolating the capacitance of the touch sensor from the compensation capacitor; and applying a reference voltage at the input node and a supply voltage at the compensation capacitor. The application of the reference voltage at the input node induces a second amount of charge proportional to a difference between the first voltage and the reference voltage on an integration capacitor. The method also includes determining a first difference between the first voltage and the reference voltage based on a second amount of charge on the integration capacitor; and determining whether a touch input to the touch sensor has occurred based on the first difference.