System for extending the lifespan of a touch screen assembly

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.

2. The system of claim 1 wherein at least one of the one or more output voltages of the touch screen assembly is an analog signal.

3. The system of claim 1 wherein the controller is further configured to adjust the programmable threshold voltage to account for temperature fluctuations.

4. The system of claim 1 wherein the controller is further configured to determine the coordinates of the pressure exerted upon the touch screen assembly.

5. The system of claim 1 wherein the touch screen assembly, the analog multiplexer/demultiplexer, the resistor, the sensing circuit, the comparator, and the controller are disposed in a handheld electronic device.

6. A sensor circuit for extending the lifespan of a touch screen, the sensor circuit comprising:

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 four output voltages of a four wire 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 touch screen assembly comprises a plurality of layers including:

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;

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.

7. The sensor circuit of claim 6 wherein at least one of the one or more output voltages of the touch screen assembly is an analog signal.

8. The sensor circuit of claim 6 wherein the controller is further configured to adjust the programmable threshold voltage to account for temperature fluctuations.

9. The sensor circuit of claim 6 wherein the controller is further configured to determine the coordinates of the pressure exerted upon the touch screen assembly.

10. The sensor circuit of claim 6 wherein the touch screen assembly, the analog multiplexer/demultiplexer, the resistor, the sensing circuit, the comparator, and the controller are disposed in a handheld electronic device.