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System for extending the lifespan of a touch screen assembly

  • US 10,019,099 B2
  • Filed: 03/12/2013
  • Issued: 07/10/2018
  • Est. Priority Date: 04/28/2006
  • Status: Active Grant
First Claim
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1. A system for extending the lifespan of a touch screen, the system comprising:

  • a four wire touch screen assembly comprising a plurality of layers, the touch screen assembly having four output voltages that are related to a pressure exerted upon the touch screen assembly, wherein two of the four output voltages are related to the pressure exerted upon the touch screen assembly with respect to an x-dimension and the other two of the four output voltages are related to the pressure exerted upon the touch screen assembly with respect to a y- dimension, wherein the plurality of layers include;

    an outer protective layer;

    a resistive digitizer film, wherein the outer protective layer substantially covers and protects the resistive digitizer film; and

    a digitizing element, wherein the resistive digitizer film is located between the outer protective layer and the digitizing element;

    an analog multiplexer/demultiplexer having four input voltages and an output voltage, wherein the four input voltages of the analog multiplexer/demultiplexer are related to the four output voltages of the touch screen assembly;

    a resistor configured to receive the output voltage of the analog multiplexer/demultiplexer such that a voltage across the resistor is equal to the output voltage of the analog multiplexer/demultiplexer;

    a first capacitor coupled to a first wire carrying a first output voltage of the four output voltages, the first output voltage related to the pressure exerted upon the touch screen assembly with respect to the x-dimension, the first capacitor further coupled to a ground;

    a second capacitor coupled to a second wire carrying a second output voltage of the four output voltages, the second output voltage related to the pressure exerted upon the touch screen assembly with respect to the y-dimension, the second capacitor further coupled to the ground;

    a sensing circuit configured to measure the voltage across the resistor;

    a comparator configured to perform operations including;

    accessing the measured voltage across the resistor;

    comparing the measured voltage across the resistor with a programmable threshold voltage; and

    initiating a signal indicating that a valid touch has occurred when the measured voltage across the resistor is at least equal to the programmable threshold voltage; and

    a controller configured to;

    receive a hardware interrupt indicating that the pressure is being exerted upon the touch screen assembly; and

    increase the programmable threshold voltage to account for a loss of tension of the resistive digitizer film.

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