Capacitive Touchscreen System with Drive-Sense Circuits

• US 20110298745A1
• Filed: 06/02/2010
• Published: 12/08/2011
• Est. Priority Date: 06/02/2010
• Status: Active Grant

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: Avago Technologies ECBU IP Singapore Pte Limited (Broadcom, Inc.)
• Inventors: Souchkov, Vitali
• Granted Patent: US 8,766,930 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• 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-sense circuits operably connected to X and Y lines of the touchscreen may be interchangeably and selectably configured as either sense circuits or drive circuits by a drive/sense processor operably connected thereto.

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 touch devices brought into proximity thereto;

first drive-sense circuits, one each of such first drive-sense circuits being operably connectable to a corresponding one of the first plurality of traces by switching circuitry, each first drive-sense circuit being operably connectable to its corresponding trace and to a first amplifier, a first capacitor being operably connected to a first negative input and a first output of the first amplifier, and to a first comparator operably connected to the first output of the first amplifier,

second drive-sense circuits, one each of such second drive-sense circuits being operably connectable to a corresponding one of the second plurality of traces by switching circuitry, each second drive-sense circuit being operably connectable to its corresponding trace and a second amplifier, a second capacitor being operably connected to a second negative input and a second output of the second amplifier, and to a second comparator operably connected to the second output of the second amplifier, and

a drive/sense processor operably connected to the first and second drive-sense circuits, respectively, and configured;

(a) to control the first plurality of first drive-sense circuits to drive at least some of the first plurality of traces and to control the second plurality of second drive-sense circuits to sense at least some of the mutual capacitances through the second plurality of traces, and (b) to control the second drive-sense circuits to drive at least some of the second plurality of traces and to control the first drive-sense circuits to sense at least some of the mutual capacitances through the first plurality of traces.

2. The capacitive touchscreen system of claim 1, wherein the first and second drive-sense circuits comprise charge integrator circuits.

3. The capacitive touchscreen system of claim 1, wherein the capacitors in the first and second drive-sense circuits are sample-and-hold capacitors.

4. The capacitive touchscreen system of claim 1, wherein each of the first and Second drive-sense circuits comprises logic circuitry configured to permit each of the first and second drive-sense circuits to operate selectably as drive circuits or as sense circuits.

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

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

7. The capacitive touchscreen system of claim 1, wherein each of the comparators in the first and second drive-sense circuits is configured to detect a voltage associated with its corresponding mutual capacitance at a predetermined threshold voltage.

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

9. The capacitive touchscreen system of claim 1, wherein the drive/sense processor is further configured to control the first and second drive-sense circuits to sense substantially simultaneously multiple mutual capacitances on the touchscreen.

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

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

12. 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.

13. The capacitive touchscreen system of claim 1, wherein the drive/sense processor is further configured to control sensing selected ones of the mutual capacitances on the basis of the locations of touches that have already been detected.

14. 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.

15. 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.

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

17. 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.

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

19. The capactive touchscreen system of claim 1, wherein the first and second pluralities of electrically conductive traces comprise iridium tin oxide (“

ITO”

).

20. The capacitive touchscreen system of claim 1, wherein the first and second pluralities of electrically conductive traces form a 9×

16 sensor array, an 8×

12 sensor array, or a 12×

20 sensor array.

21. The capacitive touchscreen system of claim 1, wherein a liquid crystal display is disposed beneath the first and second pluralities of electrically conductive traces.

22. The capacitive touchscreen system of claim 1, wherein an image display is disposed beneath the first and second pluralities of electrically conductive traces.

23. 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.

24. The capacitive touchscreen system of claim 21, wherein the substrate is substantially optically transparent.

25. They capacitive touchscreen system of claim 1, wherein the first and second drive-sense circuits are incorporated into an integrated circuit.

26. 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 a household appliance, and an electronic device.

27. 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 touch devices brought into proximity thereto, first drive-sense circuits, one each of such first drive-sense circuits being operably connectable to a corresponding one of the first plurality of traces by switching circuitry, each first drive-sense circuit being operably connectable to its corresponding trace and to a first amplifier, a first capacitor being operably connected to a first negative input and a first output of the first amplifier, and to a first comparator operably connected to the first output of the first amplifier, second drive-sense circuits, one each of such second drive-sense circuits being operably connectable to a corresponding one of the second plurality of traces by switching circuitry, each second drive-sense circuit being operably connectable to its corresponding trace and a second amplifier, a second capacitor being operably connected to a second negative input and a second output of the second amplifier, and to a second comparator operably connected to the second output of the second amplifier, and a drive/sense processor operably connected to the first and second drive-sense circuits, respectively, and configured:

(i) to control the first drive-sense circuits to drive at least some of the first plurality of traces and to control the second drive-sense circuits to sense at least some of the mutual capacitances through the second plurality of traces, and (ii) to control the second drive-sense circuits to drive at least some of the second plurality of traces and to control the first drive-sense circuits to sense at least some of the Mutual capacitances through the first plurality of traces, the method comprising;

(a) driving the first plurality of electrically conductive traces through the first drive-sense circuits;

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

(c) driving the second plurality of electrically conductive traces through the second drive-sense circuits;

(d) sensing the mutual capacitances through the first plurality of electrically conductive traces and the first drive-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.

28. The method of claim 27, further comprising driving substantially simultaneously the first plurality of electrically conductive traces through the first or second drive-sense circuits.

29. The method of claim 27, further comprising driving substantially simultaneously the second plurality of electrically conductive traces through the first or second drive-sense circuits.

30. The method of claim 27, further comprising sensing, substantially simultaneously at least some of the mutual capacitances through the first drive-sense circuits.

31. The method of claim 27, further comprising sensing substantially simultaneously at least some of the mutual capacitances through the second drive-sense circuits.

32. The method of claim 27, wherein sensing comprises detecting voltages associated with mutual capacitances.

33. The method of claim 27, further comprising detecting the locations of multiple simultaneous or near-simultaneous touches on the touchscreen through comparators detecting voltages associated with the mutual capacitances corresponding thereto.

34. The method of claim 27, further comprising driving selected ones of the first and second drive-sense circuits on the basis of the locations of touches that have already been detected.

35. The method of claim 27, further comprising controlling sensing selected ones of the first and second drive-sense circuits on the basis of locations of touches that have already been detected.

36. The method of claim 27, further comprising generating tags associated with the locations of detected touches.

37. The method of claim 27, further comprising generating tags associated with the magnitudes of detected touches.