Current mirror self-capacitance measurement

摘要

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.

主权项

1. A method comprising:
performing a routine, wherein the routine comprises:
applying a first current to a capacitance of a touch sensor, the application of the first current to the capacitance modifying a voltage at the capacitance from a reference voltage level to a first pre-determined voltage level;applying a second current to an integration capacitor, the second current being proportional to the first current, the application of the second current to the integration capacitor modifying a voltage at the integration capacitor from the reference voltage level to a first charging voltage level; andinterrupting the application of the second current when the voltage at the capacitance is substantially equal to a first voltage level limit, the first voltage level limit being lower than the first pre-determined voltage level; repeating the routine a number of times until the voltage at the integration capacitor satisfies a first threshold voltage level; and determining whether a touch input to the touch sensor has occurred based at least in part on the number of times the routine is performed.