Patent ID: 8593432
Filing Date: 2013-11-26
Classification: G06F

Abstract:
1. A method for measuring the charge on a sense line of a capacitive touchpad using a sample and hold measurement circuit, said method comprising the steps of: 1) providing a sample and hold measurement circuit including a sample capacitor for integrating charge, an Op Amp that functions as an Integrator and a Comparator, and an integrating capacitor for operating with the Op Amp; 2) discharging all charge on the sample capacitor during a RESET PHASE; 3) coupling a sense line from a touchpad to the sample capacitor; 4) integrating charge from the sense line to the sample capacitor during an ACQUISITION PHASE; 5) adding charge to the integrating capacitor during a MEASUREMENT PHASE until the charge on the integrating capacitor is equal to the charge on sample capacitor; and 6) toggling an output of the Op Amp.