Capacitance sensing circuits, methods and systems having ground insertion electrodes

• US 9,927,926 B2
• Filed: 09/27/2011
• Issued: 03/27/2018
• 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
• Primary Examiner(s): Phan, Minh
• Assistant Examiner(s): Andrews, Brent J
• Application Number:
  US13/246,467
• Publication Number:
  US 20130015868A1
• Time in Patent Office: 2,373 Days
• Field of Search: 324176, 324650-693, 345173
• 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, wherein;

at least one of the plurality of TX electrodes is coupled to a TX node and at least one other of the plurality of TX electrodes is coupled to a ground node in a first mode,

the at least one other of the plurality of TX electrodes is coupled to the TX node and the at least one of the plurality of TX electrodes is coupled to the ground node in a second mode, and

the TX electrodes are coupled to the TX node or the ground node through a switch;

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 from the TX node in the first mode, wherein each of the first electrodes comprises a plurality of sensing plates electrically connected to one another, wherein all of the sensing plates of the plurality of first electrodes are formed on one flat coplanar surface; and

a plurality of second electrode 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, further including:

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

3. The capacitance sensing system claim 1, wherein:

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

4. The capacitance sensing system claim 3, wherein:

at least one sensing plate of the first electrodes includes an opening formed therein; and

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

5. 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.

6. 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.

12. The capacitance sensing system of claim 1 further comprising:

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

7. A method, comprising:

driving at least a first transmit (TX) electrode with a transmit signal by coupling the first TX electrode to a TX node and coupling a second TX electrode to a ground node in a first mode;

driving the second TX electrode with the transmit signal by coupling the second TX electrode to the TX node and coupling the first TX electrode to the ground node in a second mode, wherein the TX electrodes are coupled to the TX node or the ground node through a switch;

detecting a mutual capacitance between a plurality of receive (RX) electrodes and the first TX electrode, wherein each of the plurality of RX electrodes comprises a plurality of sensing plates electrically connected to one another, all of the sensing plates formed on one coplanar, flat surface; and

maintaining a connection between a plurality of second electrode structures and a ground node at least while the first TX electrode is driven with the transmit signal from the TX node in the first mode, the plurality of second electrode structures interspersed with the RX electrodes.

8. The method of claim 7, wherein

at least one of the plurality of second electrode structure structures is formed between each adjacent first electrode of the plurality of first electrodes.

9. The method of claim 7, further including:

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

13. The method of claim 7 further comprising:

in at least a second sensing phase,

driving the at least one transmit (TX) electrode with the 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.

10. A capacitance sensing system, comprising:

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

all of the conductive plates are formed on one flat coplanar surface, and

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; and

a plurality of switch circuits that selectively connect at least some of the RX or TX electrodes to a ground node while a first TX electrode is coupled to a TX signal and the plurality of RX electrodes are coupled to a capacitance sense circuit, wherein the first TX electrode is coupled to a TX node through a first switch circuit to provide the TX signal to the first TX electrode and a second TX electrode is coupled to a ground node through a second switch in a first mode, and wherein the first TX electrode is coupled to the ground node through the first switch and the second TX electrode is coupled to the TX node through the second switch to provide the TX signal to the second TX electrode in a second mode.

11. The capacitance sensing system of claim 10, wherein:

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

14. The capacitance sensing system of claim 10, 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, and

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