Touch screen driver and methods for use therewith

• US 20070132739A1
• Filed: 12/14/2005
• Published: 06/14/2007
• Est. Priority Date: 12/14/2005
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Sigmatel LLC (NXP Semiconductors NV)
• Inventors: Felder, Matthew
• Granted Patent: US 7,821,501 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

A touch screen driver includes a conditioner module for conditioning a first input/output port of a touch screen. The conditioner module includes a precharge module for charging the first input/output port to a precharge voltage in response to a precharge signal, and a pull-up module for maintaining the precharge voltage for detecting a touch event.

Claims

1. A touch screen driver comprising:

a conditioner module, for conditioning a first input/output port of a touch screen, the conditioner module including a precharge module for charging the first input/output port to a precharge voltage in response to a precharge signal, and a pull-up module for maintaining the precharge voltage for detecting a touch event;

an output module, operably coupled to the first input/output port for detecting the touch event based on an output voltage and for generating a touch detect signal in response to the detection of the touch event; and

a controller module, operably coupled to the conditioner module and the output module, for generating the precharge signal and for generating a control signal in response to the touch detect signal.

2. The touch screen driver of claim 1 further comprising:

an input module, operably coupled to the controller module, for selectively providing an input signal having an input voltage to the first input/output port in response to the control signal, the input module including a voltage regulator for regulating the input voltage below a supply voltage.

3. The touch screen driver of claim 2 wherein the input module selectively provides the input signal to a second input/output port.

4. The touch screen driver of claim 2 wherein the input voltage is less than the precharge voltage.

5. The touch screen driver of claim 1 wherein the precharge signal includes a precharge pulse having a predetermined duration.

6. The touch screen driver of claim 1 wherein the predetermined duration is derived based on a resistor-capacitor time constant.

7. The touch screen driver of claim 1 wherein the predetermined duration is derived based on a number of clock cycles of a clock.

8. The touch screen driver of claim 1 wherein the predetermined duration is generated by a hardware circuit.

9. The touch screen driver of claim 1 wherein the controller module is further operable to disable the pull-up module in response to the touch event.

10. The touch screen driver of claim 1 wherein the pull-up module includes:

a transistor, operably coupled to a supply voltage, for conducting a pull-up current in response to a touch detect enable signal;

a current limiter, operably coupled to the transistor and to the first input-output port, for limiting the pull-up current.

11. The touch screen driver of claim 1 wherein the precharge module includes:

a first transistor, operably coupled to a supply voltage, for conducting a first precharge current in response to the precharge signal.

12. The touch screen driver of claim 1 wherein the precharge module includes:

a second transistor, operably coupled to a supply voltage, for conducting a second precharge current in response to the precharge signal.

13. The touch screen driver of claim 1 wherein one of the conditioner module, the output module and the controller module is implemented on a system on a chip integrated circuit.

14. A touch screen driver comprising:

a conditioner module, for conditioning a first input/output port of a touch screen, the conditioner module including a precharge module for charging the first input/output port to a precharge voltage in response to a precharge signal, and a pull-up module for maintaining the precharge voltage for detecting a touch event.

15. The touch screen driver of claim 14 further comprising:

a controller module, operably coupled to the conditioner module, for generating the precharge signal.

16. The touch screen driver of claim 15 wherein the precharge signal includes a precharge pulse having a predetermined duration.

17. The touch screen driver of claim 14 wherein the predetermined duration is derived based on a resistor-capacitor time constant.

18. The touch screen driver of claim 14 wherein the predetermined duration is derived based on a number of clock cycles of a clock.

19. The touch screen driver of claim 14 wherein the predetermined duration is generated by a hardware circuit.

20. The touch screen driver of claim 15 wherein the controller module is further operable to disable the pull-up module in response to the touch event.

21. The touch screen driver of claim 15 further comprising:

an input module, operably coupled to the controller module, for selectively providing an input signal having an input voltage to the first input/output port in response to the touch event, the input module including a voltage regulator for regulating the input voltage below a supply voltage.

22. The touch screen driver of claim 21 wherein the input module selectively provides the input signal to a second input/output port.

23. The touch screen driver of claim 21 wherein the input voltage is less than the precharge voltage.

24. The touch screen driver of claim 14 wherein the pull-up module includes:

a transistor, operably coupled to a supply voltage, for conducting a pull-up current in response to a touch detect enable signal;

a current limiter, operably coupled to the transistor and to the first input-output port, for limiting the pull-up current.

25. The touch screen driver of claim 14 wherein the precharge module includes:

a first transistor, operably coupled to a supply voltage, for conducting a first precharge current in response to the precharge signal.

26. The touch screen driver of claim 14 wherein the precharge module includes:

a second transistor, operably coupled to a supply voltage, for conducting a second precharge current in response to the precharge signal.

27. The touch screen driver of claim 15 further comprising:

an output module, operably coupled to the input/output port and the controller module, for generating a touch detect signal in response to an output voltage.

28. The touch screen driver of claim 14 wherein the conditioner module is implemented on a system on a chip integrated circuit.

29. A method comprising:

generating a precharge signal;

charging a input/output port of a touch screen to a precharge voltage in response to the precharge signal;

maintaining the precharge voltage for detecting a touch event;

detecting the touch event in response to an output voltage of the input/output port; and

generating a touch detect signal in response to an output voltage.

30. The method of claim 29 further comprising:

regulating an input voltage below a supply voltage; and

selectively providing an input signal having the input voltage to the first input/output port in response to the touch event.

31. The method of claim 30 wherein the input voltage is less than the precharge voltage.

32. The method of claim 29 wherein the precharge signal includes a precharge pulse having a predetermined duration.

33. The method of claim 29 wherein the step of maintaining a precharge voltage is disabled in response to the touch event.

34. A method comprising:

regulating an input voltage below a supply voltage; and

selectively providing an input signal having the input voltage to an input/output port of a touch screen in response to the touch event.

35. The method of claim 34 wherein the step of regulating the input voltage includes regulating the input voltage to be substantially equal to a maximum analog to digital converter input voltage level.

36. A touch screen driver comprising:

an input module, for selectively providing an input signal having an input voltage to a first input/output port of a touch screen in response to a control signal, the input module including a voltage regulator for regulating the input voltage below a supply voltage;

an output module, operably coupled to the first input/output port, for detecting the touch event based on an output voltage and for generating a touch detect signal in response to the detection of the touch event; and

a controller module, operably coupled to the input module and the output module, for generating a control signal in response to the touch detect signal.

37. The touch screen driver of claim 36 wherein the input module selectively provides the input signal to a second input/output port of the touch screen.

38. The touch screen driver of claim 36 wherein the output module includes an analog to digital converter module having a maximum analog to digital converter input voltage level and wherein the input module regulates the input voltage to be substantially equal to the maximum analog to digital converter input voltage level.

39. The touch screen driver of claim 36 wherein one of the input module, the output module and the controller module is implemented on a system on a chip integrated circuit.

40. A touch screen driver comprising:

an input module, for selectively providing an input voltage to a first input/output port of a touch screen, the input module including a regulator for regulating the input voltage below a supply voltage.

41. The touch screen driver of claim 40 wherein the input module selectively provides the input voltage to a second input/output port of the touch screen.

42. The touch screen driver of claim 40 further comprising

an analog to digital converter module for sampling and digitizing an output voltage from the first input/output port, the analog to digital converter module having a maximum analog to digital converter input voltage level;

wherein the input module regulates the input voltage to be substantially equal to the maximum analog to digital converter input voltage level.

43. The touch screen driver of claim 40 wherein the input module is implemented on a system on a chip integrated circuit.