In one embodiment, a method includes applying a first current to a capacitance of a touch sensor. The application of the first current to the capacitance for a first amount of time modifies the voltage at the capacitance from the reference voltage level to a first pre-determined voltage level. The method also includes applying a second current to an integration capacitor. The second current is proportional to the first current. The application of the second current to the integration capacitor for the first amount of time modifies the voltage at the integration capacitor from the reference voltage level to a first charging voltage level. The method also includes determining whether a touch input to the touch sensor has occurred based on the first charging voltage level.