Capacitive touchscreen system with multiplexers

• US 8,692,781 B2
• Filed: 06/02/2010
• Issued: 04/08/2014
• Est. Priority Date: 06/02/2010
• Status: Active Grant

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: PixArt Imaging Incorporated
• Inventors: Souchkov, Vitali
• Primary Examiner(s): Nguyen, Chanh
• Assistant Examiner(s): MISTRY, RAM A
• Application Number:
  US12/792,670
• Publication Number:
  US 20110298744A1
• Time in Patent Office: 1,406 Days
• Field of Search: 345/156, 345173-178
• US Class Current: 345/173
• CPC Class Codes: G06F 2203/04104 Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

Disclosed herein are various embodiments of a capacitive touchscreen system that is capable of sensing simultaneous or near-simultaneous multiple finger touches made on a capacitive touchscreen. In one embodiment, drive and sense circuits operably connected to X and Y lines of the touchscreen may be interchangeably and selectably configured to drive and sense X and Y lines of the touchscreen, respectively, or drive and sense Y and X lines, respectively, of the touchscreen, through first and second multiplexers operating under the control of a drive/sense processor.

Claims

1. A capacitive touchscreen system comprising,

a touchscreen comprising a first plurality of electrically conductive traces arranged in rows or columns, and a second plurality of electrically conductive traces arranged in rows or columns arranged at an angle with respect to the rows or columns of the first plurality of electrodes, mutual capacitances existing between the first and second pluralities of traces at locations where the first and second pluralities of traces intersect, such mutual capacitances changing in the presence of one or more fingers or other touch devices brought into proximity thereto;

a first multiplexer connected to both the first plurality of electrically conductive traces and to the second plurality of electrically conductive traces for selecting either the first plurality of electrically conductive traces or the second plurality of electrically conductive traces;

a second multiplexer connected to both the first plurality of electrically conductive traces and to the second plurality of electrically conductive traces for selecting either the first plurality of electrically conductive traces or the second plurality of electrically conductive traces;

a plurality of sense circuits operably connected to the first multiplexer, one each of such sense circuits being operably and selectably connectable to a corresponding one of the first plurality of traces or second plurality of traces under the control of a drive/sense processor operably connected thereto, each sense circuit comprising a charge integrator circuit operably connected to a corresponding comparator, and

a drive circuit operably connected to the second multiplexer and configured to drive at least some of the first plurality of traces or second plurality of traces therethrough;

wherein the drive/sense processor operably is connected to the first and second multiplexers, the plurality of sense circuits and the drive circuit, the drive/sense processor being configured to control the operation of the plurality of sense circuits to sense at least some of the mutual capacitances through the first or second pluralities of traces, the sense circuits, and the first multiplexer, and to control the operation of the drive circuit to drive at least some of the first or second pluralities of traces through the second multiplexer, the drive circuit and the first and second multiplexers being controlled by the drive/sense processor such that when the mutual capacitances are being sensed by the sense circuits through the first plurality of traces the drive circuit is driving the second plurality of traces, and further such that when the mutual capacitances are being sensed by the sense circuits through the second plurality of traces the drive circuit is driving the first plurality of traces.

2. The capacitive touchscreen system of claim 1, wherein each charge integrator circuit comprises an operational amplifier and a capacitor operably connected to a negative input and an output of the operational amplifier.

3. The capacitive touchscreen system of claim 2, wherein the capacitor is a sample-and-hold capacitor.

4. The capacitive touchscreen system of claim 1, wherein the drive/sense processor is configured to control the drive circuit such that the traces of the first or second pluralities of electrically conductive traces are driven substantially simultaneously.

5. The capacitive touchscreen system of claim 1, wherein the drive/sense processor is configured to control the plurality of sense circuits such that the traces of the first or second pluralities of electrically conductive traces are sensed substantially simultaneously.

6. The capacitive touchscreen system of claim 1, wherein the comparators in the plurality of sense circuits are configured to detect voltages associated with their corresponding mutual capacitances at respective predetermined threshold voltages.

7. The capacitive touchscreen system of claim 1, wherein at least some of the comparators in the plurality of sense circuits are configured to detect voltages associated with their corresponding mutual capacitances at predetermined high and low voltage thresholds.

8. The capacitive touchscreen system of claim 1, wherein the drive/sense processor is further configured to control the plurality of sense circuits to detect the locations of multiple simultaneous or near-simultaneous touches on the touchscreen.

9. The capacitive touchscreen system of claim 1, wherein the drive/sense processor is further configured to control driving selected ones of the first and second pluralities of traces on the basis of the locations of touches that have already been detected.

10. The capacitive touchscreen system of claim 9, wherein the detection of locations of multiple simultaneous or near-simultaneous touches on the touchscreen is carried out using comparators detecting voltages associated with the mutual capacitances corresponding thereto.

11. The capacitive touchscreen system of claim 1, wherein the drive/sense processor is further configured to control sensing selected ones of the first and second pluralities of traces on the basis of the locations of touches that have already been detected.

12. The capacitive touchscreen system of claim 1, wherein the drive/sense processor is further configured to generate tags associated with the locations of detected touches.

13. The capacitive touchscreen system of claim 1, wherein the drive/sense processor is further configured to generate tags associated with the magnitudes of detected touches.

14. The capacitive touchscreen system of claim 1, wherein the angle is about 90 degrees.

15. The capacitive touchscreen system of claim 1, wherein the first and second pluralities of electrically conductive traces are disposed in substantially parallel but vertically-offset first and second planes, respectively.

16. The capacitive touchscreen system of claim 1, wherein the first and second pluralities of electrically conductive traces are disposed in substantially the same plane.

17. The capacitive touchscreen system of claim 1, wherein the first and second pluralities of electrically conductive traces are disposed on a substrate comprising an electrically insulative material.

18. The capacitive touchscreen system of claim 17, wherein the substrate is substantially optically transparent.

19. The capacitive touchscreen system of claim 1, wherein the drive and sense circuits are incorporated into an integrated circuit.

20. The capacitive touchscreen system of claim 1, wherein the touchscreen system is incorporated into or forms a portion of an LCD, a computer display, a laptop computer, a personal data assistant (PDA), a mobile telephone, a radio, an MP3 player, a portable music player, a stationary device, a television, a stereo, an exercise machine, an industrial control, a control panel, an outdoor control device and a household appliance.

21. A capacitive touchscreen system, comprising:

a touchscreen comprising a first plurality of electrically conductive traces arranged in rows or columns, and a second plurality of electrically conductive traces arranged in rows or columns arranged at an angle with respect to the rows or columns of the first plurality of electrodes, mutual capacitances existing between the first and second pluralities of traces at locations where the first and second pluralities of traces intersect, such mutual capacitances changing in the presence of one or more fingers or other touch devices brought into proximity thereto;

a first multiplexer connected to both the first plurality of electrically conductive traces and to the second plurality of electrically conductive traces for selecting either the first plurality of electrically conductive traces or the second plurality of electrically conductive traces;

a second multiplexer connected to both the first plurality of electrically conductive traces and to the second plurality of electrically conductive traces for selecting either the first plurality of electrically conductive traces or the second plurality of electrically conductive traces;

a plurality of sense circuits operably connected to the first multiplexer and to the second multiplexer, one each of such sense circuits being operably and selectably connectable to a corresponding one of the first or second pluralities of traces under the control of a drive/sense processor operably connected thereto, each sense circuit comprising a charge integrator circuit operably connected to a corresponding comparator, and

a drive circuit operably connected to the first and second multiplexers and configured to drive at least some of the first plurality of traces or second plurality of traces therethrough;

wherein the drive/sense processor operably is connected to the first and second multiplexers, the plurality of sense circuits and the drive circuit, the drive/sense processor being configured to control the operation of the plurality of sense circuits to sense at least some of the mutual capacitances through the first or second pluralities of traces, the sense circuits, and the first or second multiplexers, and to control the operation of the drive circuit to drive at least some of the first or second pluralities of traces through the first or second multiplexers, the drive circuit and the first and second multiplexers being controlled by the drive/sense processor such that when the mutual capacitances are being sensed by the sense circuits through the first plurality of traces the drive circuit is driving the second plurality of traces, and further such that when the mutual capacitances are being sensed by the sense circuits through the second plurality of traces the drive circuit is driving the first plurality of traces.

22. The capacitive touchscreen system of claim 21, wherein each charge integrator circuit comprises an operational amplifier and a capacitor operably connected to a negative input and an output of the operational amplifier.

23. The capacitive touchscreen system of claim 22, wherein the capacitor is a sample-and-hold capacitor.

24. The capacitive touchscreen system of claim 21, wherein the drive/sense processor is configured to control the drive circuit such that the traces of the first or second pluralities of electrically conductive traces are driven substantially simultaneously.

25. The capacitive touchscreen system of claim 21, wherein the drive/sense processor is configured to control the plurality of sense circuits such that the traces of the first or second pluralities of electrically conductive traces are sensed substantially simultaneously.

26. The capacitive touchscreen system of claim 21, wherein the drive and sense circuits are incorporated into an integrated circuit.

27. The capacitive touchscreen system of claim 21, wherein the touchscreen system is incorporated into or forms a portion of an LCD, a computer display, a laptop computer, a personal data assistant (PDA), a mobile telephone, a radio, an MP3 player, a portable music player, a stationary device, a television, a stereo, an exercise machine, an industrial control, a control panel, an outdoor control device and a household appliance.

28. A method of detecting touches on a capacitive touchscreen system comprising a touchscreen comprising a first plurality of electrically conductive traces arranged in rows or columns, and a second plurality of electrically conductive traces arranged in rows or columns arranged at an angle with respect to the rows or columns of the first plurality of electrodes, mutual capacitances existing between the first and second pluralities of traces at locations where the first and second pluralities of traces intersect, such mutual capacitances changing in the presence of one or more fingers or other touch devices brought into proximity thereto, a first multiplexer connected to both the first plurality of electrically conductive traces and to the second plurality of electrically conductive traces for selecting either the first plurality of electrically conductive traces or the second plurality of electrically conductive traces, a second multiplexer connected to both the first plurality of electrically conductive traces and to the second plurality of electrically conductive traces for selecting either the first plurality of electrically conductive traces or the second plurality of electrically conductive traces, a plurality of sense circuits operably connected to the first multiplexer, one each of such sense circuits being operably and selectably connectable to a corresponding one of the first plurality of traces or second plurality of traces under the control of a drive/sense processor operably connected thereto, each sense circuit comprising a charge integrator circuit operably connected to a corresponding comparator, and a drive circuit operably connected to the second multiplexer and configured to drive at least some of the first plurality of traces or second plurality of traces therethrough, wherein the drive/sense processor operably is connected to the first and second multiplexers, the plurality of sense circuits and the drive circuit, the drive/sense processor being configured to control the operation of the plurality of sense circuits to sense at least some of the mutual capacitances through the first or second pluralities of traces, the sense circuits, and the first multiplexer, and to control the operation of the drive circuit to drive at least some of the first or second pluralities of traces through the second multiplexer, the drive circuit and the first and second multiplexers being controlled by the drive/sense processor such that when the mutual capacitances are being sensed by the sense circuits through the first plurality of traces the drive circuit is driving the second plurality of traces, and further such that when the mutual capacitances are being sensed by the sense circuits through the second plurality of traces the drive circuit is driving the first plurality of traces, the method comprising:

(a) driving the first plurality of electrically conductive traces through the drive circuit;

(b) sensing the mutual capacitances through the second plurality of electrically conductive traces and the sense circuits;

(c) driving the second plurality of electrically conductive traces through the drive circuit;

(d) sensing the mutual capacitances through the first plurality of electrically conductive traces and the sense circuits, and

(e) detecting the locations of one or more touches on the touchscreen on the basis of sensed mutual capacitances exceeding predetermined voltage thresholds.

29. The method of claim 28, further comprising driving substantially simultaneously at least some of the first or second pluralities of electrically conductive traces with the drive circuit.

30. The method of claim 28, further comprising sensing substantially simultaneously at least some of the mutual capacitances through the first or second pluralities of electrically conductive traces with the sense circuits.

31. The method of claim 28, wherein sensing comprises detecting voltages associated with the mutual capacitances that exceed predetermined threshold voltages.

32. The method of claim 28, further comprising detecting the locations of multiple simultaneous or near-simultaneous touches on the touchscreen through comparators in the sense circuits detecting voltages associated with the mutual capacitances corresponding thereto that exceed predetermined threshold voltages.

33. The method of claim 28, further comprising driving selected ones of the first or second pluralities of traces through the drive circuit on the basis of the locations of touches that have already been detected.

34. The method of claim 28, further comprising controlling sensing selected ones of the first and second pluralities of traces with the sense circuits on the basis of locations of touches that have already been detected.

35. The method of claim 28, further comprising generating tags associated with the locations of detected touches.

36. The method of claim 28, further comprising generating tags associated with the magnitudes of detected touches.

37. A method of detecting touches on a capacitive touchscreen system comprising a touchscreen comprising a first plurality of electrically conductive traces arranged in rows or columns, and a second plurality of electrically conductive traces arranged in rows or columns arranged at an angle with respect to the rows or columns of the first plurality of electrodes, mutual capacitances existing between the first and second pluralities of traces at locations where the first and second pluralities of traces intersect, such mutual capacitances changing in the presence of one or more fingers or other touch devices brought into proximity thereto, a first multiplexer connected to both the first plurality of electrically conductive traces and to the second plurality of electrically conductive traces for selecting either the first plurality of electrically conductive traces or the second plurality of electrically conductive traces, a second multiplexer connected to both the first plurality of electrically conductive traces and to the second plurality of electrically conductive traces for selecting either the first plurality of electrically conductive traces or the second plurality of electrically conductive traces, a plurality of sense circuits operably connected to the first multiplexer and to the second multiplexer, one each of such sense circuits being operably and selectably connectable to a corresponding one of the first plurality of traces or second plurality of traces under the control of a drive/sense processor operably connected thereto, each sense circuit comprising a charge integrator circuit operably connected to a corresponding comparator, and a drive circuit operably connected to the first and second multiplexers and configured to drive at least some of the first plurality of traces or second plurality of traces through the first or second multiplexers, wherein the drive/sense processor operably is connected to the first and second multiplexers, the plurality of sense circuits and the drive circuit, the drive/sense processor being configured to control the operation of the plurality of sense circuits to sense at least some of the mutual capacitances through the first or second pluralities of traces, the sense circuits, and the first or second multiplexers, and to control the operation of the drive circuit to drive at least some of the first or second pluralities of traces through the first or second multiplexers, the drive circuit and the first and second multiplexers being controlled by the drive/sense processor such that when the mutual capacitances are being sensed by the sense circuits through the first plurality of traces the drive circuit is driving the second plurality of traces, and further such that when the mutual capacitances are being sensed by the sense circuits through the second plurality of traces the drive circuit is driving the first plurality of traces, the method comprising:

(a) driving the first plurality of electrically conductive traces through the drive circuit;

(b) sensing the mutual capacitances through the second plurality of electrically conductive traces and the sense circuits;

(c) driving the second plurality of electrically conductive traces through the drive circuit;

(d) sensing the mutual capacitances through the first plurality of electrically conductive traces and the sense circuits, and

(e) detecting the locations of one or more touches on the touchscreen on the basis of sensed mutual capacitances exceeding predetermined voltage thresholds.

38. The method of claim 37, further comprising driving substantially simultaneously at least some of the first or second pluralities of electrically conductive traces with the drive circuit.

39. The method of claim 37, further comprising sensing substantially simultaneously at least some of the mutual capacitances through the first or second pluralities of electrically conductive traces with the sense circuits.

40. The method of claim 37, wherein sensing comprises detecting voltages associated with the mutual capacitances that exceed predetermined threshold voltages.

41. The method of claim 37, further comprising detecting the locations of multiple simultaneous or near-simultaneous touches on the touchscreen through comparators in the sense circuits detecting voltages associated with the mutual capacitances corresponding thereto that exceed predetermined threshold voltages.

42. The method of claim 37, further comprising driving selected ones of the first or second pluralities of traces through the drive circuit on the basis of the locations of touches that have already been detected.

43. The method of claim 37, further comprising controlling sensing selected ones of the first and second pluralities of traces with the sense circuits on the basis of locations of touches that have already been detected.

44. The method of claim 37, further comprising generating tags associated with the locations of detected touches.

45. The method of claim 37, further comprising generating tags associated with the magnitudes of detected touches.