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Capacitive touch sensing and light emitting diode drive matrix

  • US 8,780,068 B2
  • Filed: 04/19/2013
  • Issued: 07/15/2014
  • Est. Priority Date: 01/12/2009
  • Status: Expired due to Fees
First Claim
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1. A method for sensing actuation of a capacitive touch sensor and indicating such actuation, in a system comprising:

  • a sampling capacitor having a first terminal connected to a reference potential and a second terminal;

    an analog-to-digital converter (ADC) connected to the second terminal of the sampling capacitor;

    a capacitive touch sensor having a first terminal connected to the sampling capacitor through a sampling switch and through a port switch with the reference potential and having a second terminal; and

    a light emitting diode (LED) coupled in parallel with the capacitive touch sensor;

    wherein the capacitive touch sensor and the LED use common connections;

    wherein the method comprises;

    generating a single voltage pulse and charging through the capacitive touch sensor the sampling capacitor to a first voltage in proportion to a capacitance ratio thereof, wherein when an object having a capacitance is in close proximity to the capacitive touch sensor some of the voltage pulse through the capacitive touch sensor is diverted from the sampling capacitor, and wherein the sampling capacitor is charged to a second voltage when the object is in close proximity to the capacitive touch sensor, wherein the second voltage is less than the first voltage, anddetermining said voltage on said sampling capacitor; and

    controlling the port switch and a voltage at said second terminal of the capacitive touch sensor to turn on said LED.

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