Patent ID: 7692638
Filing Date: 2010-04-06
Classification: G06F

Abstract:
1. A method for normalizing DC offset error in an event detection and demodulation circuit configured for generating a value representative of a change in a signal sensed on a column of a multi-event sensor panel, the event detection and demodulation circuit having a charge amplifier, a demodulator and offset compensation, the method comprising: floating a charge amplifier input of the charge amplifier; applying a burst demodulation signal to a demodulation input of the demodulator; applying a first voltage to an analog offset compensation input of the offset compensation; measuring an output value of the event detection and demodulation circuit to obtain the DC offset error; and subtracting the DC offset error from subsequent measured output values of the event detection and demodulation circuit when an input stimulus is applied to a row in the multi-event sensor panel.