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Noise measurement in capacitive touch sensors

  • US 9,448,267 B2
  • Filed: 01/13/2014
  • Issued: 09/20/2016
  • Est. Priority Date: 10/22/2008
  • Status: Active Grant
First Claim
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1. An apparatus comprising:

  • a drive electrode;

    a sense electrode; and

    circuitry configured to perform operations comprising;

    making, in a noise-measurement phase, a first measurement by performing operations comprising;

    providing a pre-determined amount of charge to a charge-measurement capacitor;

    transferring a first amount of charge on the sense electrode to the charge-measurement capacitor, thereby modulating the first amount of charge by the pre-determined amount of charge provided to the charge-measurement capacitor; and

    measuring a first voltage of the charge-measurement capacitor to determine the first amount of charge; and

    making, in a proximity-detection phase, a second measurement by performing operations comprising;

    providing a drive signal to the drive electrode;

    transferring a second amount of charge on the sense electrode to the charge-measurement capacitor; and

    measuring a second voltage of the charge-measurement capacitor to determine the second amount of charge.

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