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Self-capacitance measurement

  • US 9,372,582 B2
  • Filed: 04/19/2012
  • Issued: 06/21/2016
  • Est. Priority Date: 04/19/2012
  • Status: Active Grant
First Claim
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1. A method comprising:

  • modifying an amount of charge of a measurement capacitance of a touch sensor, the modified amount of charge resulting in a voltage at the measurement capacitance being a first pre-determined voltage level;

    applying charge to an electrode associated with the measurement capacitance resulting in a first pre-determined amount of charge on the measurement capacitance, the application of the charge to the electrode resulting in the first pre-determined amount of charge on the measurement capacitance modifying the voltage at the measurement capacitance from the first pre-determined voltage level to a first charging voltage level;

    transferring a portion of the charge on the measurement capacitance to a sampling capacitance such that a voltage level of the sampling capacitance increases as a function of a first difference between the first charging voltage level resulting from the first pre-determined amount of charge and a reference voltage level, and such that the voltage at the measurement capacitance is modified from the first charging voltage level to the reference voltage level, wherein the reference voltage level is a pre-determined voltage corresponding to the voltage obtained by applying the first pre-determined amount of charge to the electrode when a touch input has not occurred;

    measuring the first difference between the first charging voltage level resulting from the first pre-determined amount of charge and the reference voltage level by measuring the voltage level of the sampling capacitance; and

    determining whether a touch input to the touch sensor has occurred based at least in part on the voltage level of the sampling capacitance.

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