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Methods and circuits for measuring mutual and self capacitance

  • US 9,494,628 B1
  • Filed: 09/25/2013
  • Issued: 11/15/2016
  • Est. Priority Date: 02/27/2008
  • Status: Active Grant
First Claim
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1. A capacitance measurement circuit comprising:

  • a capacitance to current conversion circuit configured to operate in a self capacitance mode in a first operational state and configured to operate in a mutual capacitance mode in a second operational state; and

    a current to code conversion circuit configured to output a digital value representative of a current generated by the capacitance to current conversion circuit;

    wherein;

    when the capacitance to current conversion circuit is configured to operate in the self capacitance mode, the capacitance to current conversion circuit comprises a sense capacitor between a first voltage potential and a plurality of switches, wherein the plurality of switches are configured to couple the sense capacitor alternately to a second voltage potential and to the current to code conversion circuit; and

    when the capacitance to current conversion circuit is configured to operate in the mutual capacitance mode, the capacitance to current conversion circuit comprises a sense capacitor between a first electrode and a second electrode, the first electrode is coupled to an alternating voltage signal, and the second electrode is coupled to the current to code conversion circuit.

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