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Error compensation for multi-touch surfaces

  • US 7,692,638 B2
  • Filed: 01/03/2007
  • Issued: 04/06/2010
  • Est. Priority Date: 01/03/2007
  • Status: Active Grant
First Claim
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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.

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