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Self capacitance touch sensing

  • US 10,061,444 B2
  • Filed: 10/30/2013
  • Issued: 08/28/2018
  • Est. Priority Date: 07/31/2013
  • Status: Active Grant
First Claim
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1. A touch sensitive device comprising:

  • a cancelation circuit comprising a numerically controlled oscillator coupled to an input of a push/pull current source, the push/pull current source capable of generating a cancelation signal based on parasitic capacitance affecting a self capacitance signal, wherein;

    the cancelation circuit is configured to generate a time-varying signal and scale the time-varying signal to generate an amplitude-controlled time-varying signal based on the parasitic capacitance to adjust a magnitude of the cancelation signal, the amplitude-controlled time-varying signal controlling the magnitude of the cancelation signal generated by the push/pull current source, andthe cancelation signal is coupled to the self capacitance signal so as to cancel the parasitic capacitance from the self capacitance signal; and

    a sense circuit capable of receiving the self capacitance signal with the parasitic capacitance canceled therefrom and a stimulation signal, and outputting a touch signal in response to the self capacitance signal with the parasitic capacitance canceled therefrom and the stimulation signal.

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