CAPACITIVE TOUCH SENSOR SYSTEM

• US 20100051354A1
• Filed: 08/28/2008
• Published: 03/04/2010
• Est. Priority Date: 08/28/2008
• Status: Active Grant

• Current Assignee: STMicroelectronics Asia Pacific Pte Limited (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Asia Pacific Pte Limited (STMicroelectronics NV)
• Inventors: Ng, Chee Yu, Ningrat, Kusuma Adi, Noviello, Giuseppe
• Granted Patent: US 8,963,843 B2
• Time in Patent Office: Days
• US Class Current: 178/18.60
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/044 by capacitive means
• 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

A method of matrix sensing using delay-based capacitance sensing, including using X-axis lines as active lines for capacitance measurements and using Y-axis lines as a disturbance to identify the location of a touch in a key matrix is disclosed. A sensing signal is applied to the X-axis lines, and a disturbance signal is applied to the Y-axis lines. If a location is touched, cross-capacitance is reduced, which is measured by sweeping data along the X-axis lines.

Claims

1. A method of matrix sensing using delay-based capacitance sensing, the method comprising:

using a plurality of X-axis lines as active lines for capacitance measurements; and

using a plurality of Y-axis lines as a disturbance to identify the location of a touch in a key matrix.

2. The method of claim 1 wherein a sensing signal is applied to the X-axis lines.

3. The method of claim 1 wherein a disturbance signal is applied to the Y-axis lines.

4. The method of claim 1 wherein if a location is touched, cross-capacitance is reduced, which is measured by sweeping data along the X-axis lines.

5. The method of claim 1 further comprising using a single X-axis line and N Y-axis lines.

6. The method of claim 5 wherein a maximum number of keys that can be pressed along the X-axis line is equal to N−

1.

7. The method of claim 1 further comprising performing the method in a matrix configuration.

8. The method of claim 1 further comprising performing the method in a diamond-shaped matrix.

9. The method of claim 1 further comprising an M×

N matrix, wherein M is the number of lines in the X-axis, N is the number of lines in the Y-axis, and assuming the maximum number of channels affected by a touch is three, the maximum number of touches allowed in a single X-line is (N/3−

1).

10. The method of claim 1 wherein “

ghost touch”

is substantially eliminated without using an additional matrix channel.

11. A touch pad or touch screen comprising:

a plurality of X-axis lines used as active lines for capacitance measurements; and

a plurality of Y-axis lines used as a disturbance to identify the location of a touch in a key matrix.

12. The touch pad or touch screen of claim 11 further comprising a sensing signal applied to the X-axis lines.

13. The touch pad or touch screen of claim 11 further comprising a disturbance signal applied to the Y-axis lines.

14. The touch pad or touch screen of claim 11 wherein if a location is touched, cross-capacitance is reduced, which is measured by sweeping data along the X-axis lines.

15. The touch pad or touch screen of claim 11 further comprising using a single X-axis line and N Y-axis lines.

16. The touch pad or touch screen of claim 15 wherein a maximum number of keys that can be pressed is equal to N−

1.

17. The touch pad or touch screen of claim 11 further comprising a matrix configuration.

18. The touch pad or touch screen of claim 11 further comprising a diamond-shaped matrix.

19. The touch pad or touch screen of claim 11 further comprising an M×

N matrix, wherein M is the number of lines in the X-axis, N is the number of lines in the Y-axis, and assuming the maximum number of channels affected by a touch is three, the maximum number of touches allowed in a single X-line is (N/3−

1).

20. The touch pad or touch screen of claim 11 wherein “

ghost touch”

is substantially eliminated without using an additional matrix channel.