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Capacitive sensing array modulation

  • US 9,880,675 B2
  • Filed: 04/11/2014
  • Issued: 01/30/2018
  • Est. Priority Date: 04/13/2012
  • Status: Active Grant
First Claim
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1. An electronic device, comprising:

  • a fingerprint sensor comprising;

    a sensor pad;

    a dielectric positioned above the sensor pad; and

    an electrically conductive ring surrounding the sensor pad and the dielectric, the electrically conductive ring at least partially elevated with respect to the sensor pad and the dielectric;

    a modulating circuit electrically connected to the fingerprint sensor and configured to maintain the electrically conductive ring at a constant voltage having an absolute value less than four volts relative to a system ground, the modulating circuit configured to;

    provide a first modulated voltage to the sensor pad; and

    provide a second modulated voltage to the sensor pad, the second modulated voltage lower than the first modulated voltage and greater than the system ground;

    wherein;

    a relative voltage difference between the first modulated voltage and the second modulated voltage is received by the sensor pad as a sensor pad supply voltage.

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