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SENSING CIRCUIT FOR USE WITH CAPACITIVE TOUCH PANEL

  • US 20110090173A1
  • Filed: 10/12/2010
  • Published: 04/21/2011
  • Est. Priority Date: 10/19/2009
  • Status: Active Grant
First Claim
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1. A sensing circuit for use with a receiving electrode of a capacitive touch panel, a mutual capacitance existing between a driving electrode of the capacitive touch panel and the receiving electrode, the driving electrode receiving a driving signal, the sensing circuit comprising:

  • an operation amplifier having a positive input terminal, a negative input terminal and an output terminal, wherein a reference voltage is inputted into the positive input terminal of the operation amplifier;

    a first switch connected between the receiving electrode and the negative input terminal of the operation amplifier;

    a second switch connected between the negative input terminal and the output terminal of the operation amplifier;

    a first feedback capacitor;

    a second feedback capacitor;

    a third switch having a first terminal connected to the negative input terminal of the operation amplifier and a second terminal connected to a first terminal of the first feedback capacitor;

    a fourth switch having a first terminal connected to a second terminal of the first feedback capacitor and a second terminal connected to the output terminal of the operation amplifier;

    a fifth switch having a first terminal connected to the negative input terminal of the operation amplifier and a second terminal connected to a first terminal of the second feedback capacitor; and

    a sixth switch having a first terminal connected to a second terminal of the second feedback capacitor and a second terminal connected to the output terminal of the operation amplifier,wherein the driving signal generates at least one pulse during a driving cycle, wherein in response to a rising edge of the pulse, the first switch, the second switch, the third switch, the fourth switch, the fifth switch and the sixth switch are controlled, so that the first feedback capacitor is charged in a first charging direction, wherein in response to a falling edge of the pulse, the first switch, the second switch, the third switch, the fourth switch, the fifth switch and the sixth switch are controlled, so that the second feedback capacitor is charged in a second charging direction.

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