CAPACITANCE SENSING CIRCUITS, METHODS AND SYSTEMS HAVING GROUND INSERTION ELECTRODES

• US 20130015868A1
• Filed: 09/27/2011
• Published: 01/17/2013
• Est. Priority Date: 07/15/2011
• Status: Active Grant

• Current Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Peng, Tao
• Granted Patent: US 9,927,926 B2
• Time in Patent Office: Days
• US Class Current: 324/688
• 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 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• 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
• CPC Class Codes: G06F 3/0448 Details of the electrode shape, e.g. for enhancing the detection of touches, for generating specific electric field shapes, for enhancing display quality

Abstract

A capacitance sensing system can include a plurality of transmit (TX) electrodes disposed in a first direction; a plurality of first electrodes disposed in a second direction and coupled to the TX electrodes by a mutual capacitance, and coupled to a capacitance sense circuit when at least one TX electrode receives a transmit signal; and a plurality of second electrodes structures, interspersed with the first electrodes and coupled to a ground node at least while the one TX electrode receives the transmit signal.

Claims

1. A capacitance sensing system, comprising:

a plurality of transmit (TX) electrodes disposed in a first direction;

a plurality of first electrodes disposed in a second direction and coupled to the TX electrodes by a mutual capacitance, and coupled to a capacitance sense circuit when at least one TX electrode receives a transmit signal; and

a plurality of second electrodes structures, interspersed with the first electrodes and coupled to a ground node at least while the one TX electrode receives the transmit signal.

2. The capacitance sensing system claim 1, wherein:

the second electrode structures have a static connection to the ground node.

3. The capacitance sensing system claim 1, further including:

a plurality of electrode switches that selectively couple the second electrode structures or first electrodes to a shield signal.

4. The capacitance sensing system claim 1, further including:

a plurality of electrode switches that selectively isolate the second electrode structures or first electrodes.

5. The capacitance sensing system claim 1, wherein:

the first electrodes and second electrode structures alternate with one another in the second direction.

6. The capacitance sensing system claim 5, wherein:

each first electrodes comprises a plurality of sensing plates formed on a flat surface and electrically connected to one another, each sensing plate having an opening formed therein; and

the second electrode structures are formed within the openings of the first electrode sensing plates.

7. The capacitance sensing system claim 1, further including:

a plurality of electrode switches that selectively couple to the first electrodes and second electrode structures between the ground node and the capacitance sense circuit.

8. The capacitance sensing system claim 1, wherein:

the TX and the first electrodes each comprise a plurality of sensing plates formed on a flat surface and electrically connected to one another by narrow sections, including bridging connections that extend over the flat surface and non-bridging connections formed on the flat surface.

9. The capacitance sensing system claim 1, further including:

a display device physically coupled to the TX electrodes, first electrodes and second electrode structures, and configured to transmit images through the TX electrodes, first electrodes, and second electrode structures.

10. A method, comprising:

in at least a first sensing phase,

driving at least one transmit (TX) electrode with a transmit signal;

detecting a mutual capacitance between first electrodes and the at least one TX electrode; and

maintaining a connection between second electrode structures and a ground node at least while the one TX electrode is driven with the transmit signal, the second electrode structures being interspersed with the first electrodes.

11. The method of claim 10, wherein

maintaining the connection between the second electrode structures and the ground node includes enabling a static connection to the ground node while a mutual capacitance is detected with the second electrodes.

12. The method of claim 10, wherein

in at least a second sensing phase,

driving at least one transmit (TX) electrode with a transmit signal;

detecting a mutual capacitance between second electrode structures and the at least one TX electrode; and

maintaining a connection between the first electrodes and the ground node at least while the one TX electrode is driven with the transmit signal.

13. The method of claim 12, wherein

at least one second electrode structure is formed between each adjacent first electrode.

14. The method of claim 10, further including:

maintaining a connection between fourth electrode structures and the ground node at least while the one TX electrode is driven with the transmit signal, the fourth electrode structures being interspersed with the TX electrodes.

15. The method of claim 10, further including:

displaying an image through the TX electrodes, first electrodes, and second electrode structures with a display device.

16. A capacitance sensing system, comprising:

a plurality of conductive plates formed on a surface and joined to one another by narrow sections to form transmit (TX) and receive (RX) electrodes; and

switch circuits that selectively connect at least some of the RX or TX electrodes to a ground node while at least one TX electrode is coupled to a TX signal and a plurality of RX electrodes are coupled to a capacitance sense circuit.

17. The capacitance sensing system of claim 16, wherein:

the switch circuits further selectively connect at least some of the TX or RX electrodes to a shield signal.

18. The capacitance sensing system of claim 16, wherein:

the switch circuits further selectively electrically isolate at least some of the TX or RX electrodes.

19. The capacitance sensing system of claim 16, wherein:

the TX electrodes include alternating first and second TX electrodes; and

the switch circuits connect the first TX electrodes to the ground node while the second TX electrodes are driven with the TX signal, and connect the second TX electrodes to the ground node while the first TX electrodes are driven with the TX signal.

20. The capacitance sensing system of claim 16, wherein:

the conductive plates of at least the TX electrodes each include

a first section having an opening formed therein, and

a second section that extends into the opening of a first section of an adjacent TX electrode.