Touch screen driver and methods for use therewith

• US 7,821,501 B2
• Filed: 12/14/2005
• Issued: 10/26/2010
• Est. Priority Date: 12/14/2005
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: SigmaTel Incorporated (NXP Semiconductors NV)
• Inventors: Felder, Matthew D.
• Primary Examiner(s): Abdulselam; Abbas I
• Application Number:
  US11/304,306
• Publication Number:
  US 20070132739A1
• Time in Patent Office: 1,777 Days
• Field of Search: 345/173, 345/174, 345/175, 345/176, 345/180, 345/156, 345/158, 178/18.01, 178/18.06, 178/18.03, 178/18.04, 178/18.05, 178/19.05, 178/19.01, 178/19.03, 235/462.46, 710/20, 701/1, 715/700
• 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 at the first input/output port until a touch event;

an output module, operably coupled to the first input/output port for detecting the touch event based on a change in a voltage at the input/output port from the precharge voltage to another voltage resulting from the touch event, 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.

2. The touch screen driver of claim 1, wherein the controller module is for generating a control signal in response to the touch detect signal and 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 5 wherein the predetermined duration is derived based on a resistor-capacitor time constant.

7. The touch screen driver of claim 5 wherein the predetermined duration is derived based on a number of clock cycles of a clock.

8. The touch screen driver of claim 5 wherein the predetermined duration is generated by a hardware circuit.

9. The touch screen driver of claim 1 wherein the controller module is further 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; and

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 11 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 the pull-up module is configured to maintain the precharge voltage while a touch detect enable signal is asserted, the touch detect enable signal different from the precharge signal.

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 until a touch event at the touch screen.

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 16 wherein the predetermined duration is derived based on a resistor-capacitor time constant.

18. The touch screen driver of claim 16 wherein the predetermined duration is derived based on a number of clock cycles of a clock.

19. The touch screen driver of claim 16 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 25 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 first 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 an 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 until the touch event;

detecting the touch event in response to a change in an output voltage of the input/output port from the precharge voltage to a second voltage, the change resulting from the touch event; and

generating a touch detect signal in response to the touch event.

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.