Granted Patent B2

US 6,961,015 · App. 10/295,559 · Granted Nov 1, 2005

Abstract

Claims (27)

1. A circuit comprising:

an analog circuit adapted to measure a voltage at two separate input terminals relative to a reference voltage;

a counter; and

a digital controller, coupled to the analog circuit and the counter, the digital controller adapted to control the counter and the analog circuit to define a time period during which the voltage is measured and convert the voltage measured to a digital value.

2. The circuit of claim 1 , wherein the analog circuit comprises:

an amplifier;

a capacitor coupled to the amplifier; and

a comparator coupled to the amplifier and the capacitor, the capacitor storing a charge corresponding to the voltage, wherein the time measured by the counter required by the capacitor to dissipate its charge represents the digital value.

3. The circuit of claim 1 , wherein the circuit determines a location on a touch screen display.

4. The circuit of claim 1 , wherein the circuit comprises a quad-slope analog-to-digital converter.

5. A touch screen display circuit comprising:

means for measuring a voltage at two separate input terminals which represent a location on a touch screen display where pressure was applied;

means for defining a time period during which the voltage is measured; and

means for converting the voltage to a digital value.

6. The circuit of claim 5 , wherein the means for measuring a voltage comprises an amplifier and capacitor which are configured as an integrator, and the means for converting comprises a counter that measures an amount of time required for the capacitor to dissipate its charge.

7. The circuit of claim 5 , wherein the means for measuring a voltage comprises an amplifier and a capacitor which are configured as an integrator.

8. The circuit of claim 7 , wherein the means for converting comprises a counter that measures an amount of time required for the capacitor to dissipate its charge.

9. The circuit of claim 5 , wherein the circuit is adapted for use in a system which includes a source of light for the touch screen, the source of light being driven by an alternating current signal, and further wherein the means for defining a time period during which the voltage is measured is adapted to define the time period such that it includes an even number of cycles of the alternating current signal.

10. The circuit of claim 5 , wherein the means for measuring a voltage and the means for converting the voltage use a common set of electrical components for the measuring and converting.

11. A touch screen display system comprising:

a touch screen comprising first and second sheets of conductive materials positioned in a spaced apart relationship;

means coupled to the first and second sheets for measuring a voltage at two separate input terminals which represent a location on the touch screen where pressure was applied;

means for defining a time period during which the voltage is measured; and

means for converting the voltage to a digital value.

12. The system according to claim 11 , wherein:

the means for measuring a voltage comprises an amplifier and a capacitor.

13. The system according to claim 12 , wherein the means for converting comprises a counter that measures an amount of time required for the capacitor to dissipate its charge.

Assignments (14)