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Capacitive Proximity Detection Using Delta-Sigma Conversion

  • US 20140368222A1
  • Filed: 06/11/2014
  • Published: 12/18/2014
  • Est. Priority Date: 06/12/2013
  • Status: Active Grant
First Claim
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1. A proximity detection system, said system comprising:

  • a comparator having first and second inputs and an output, wherein the second input is coupled with a reference voltage and the first input is coupled with a holding capacitor;

    a capacitive sensor;

    a switch for coupling the capacitive sensor alternately to a voltage and the holding capacitor;

    a clock having an output;

    a flip-flop having an input coupled with the output of the comparator, a clock input coupled to the output of the clock and an output;

    a feedback resistor coupled between the output of the flip-flop and the first input of the comparator;

    a duty cycle counter having a clock input coupled to the output of the clock, a reset input, an enable input coupled to the output of the flip-flop, and an output for providing a number of clock outputs counted, wherein the duty cycle counter only counts the clock outputs when the enable input thereof is at a first logic level; and

    a circuit for controlling the switch whenever the output of the flip-flop goes from a second logic level to the first logic level;

    wherein the number of clock outputs counted are used in determining proximity of an object to the capacitive sensor.

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