ACTIVE CANCELING OF DISPLAY NOISE IN SIMULTANEOUS DISPLAY AND TOUCH SENSING

• US 20170090671A1
• Filed: 09/30/2015
• Published: 03/30/2017
• Est. Priority Date: 09/30/2015
• Status: Active Grant

• Current Assignee: Omnivision TDDI Ontario Limited Partnership
• Original Assignee: Synaptics Incorporated
• Inventors: KHAZENI, Kasra, REYNOLDS, Joseph Kurth
• Granted Patent: US 10,061,437 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/04164 Connections between sensors and controllers, e.g. routing lines between electrodes and connection pads
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/04184 Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally
• CPC Class Codes: G06F 3/044 by capacitive means
• 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

Techniques for removing display-based corrupting components from a capacitive sensing signal when display and capacitive sensing is performed at or nearly at the same time. A routing carrying display related signals (e.g., a source signal for sub-pixel updating) may induce a corrupting current into a routing for carrying capacitive sensing signals. This corrupting current would reduce the ability to determine presence of an input object via the sensing signal. Therefore, the corrupting signal is effectively removed from a signal received from a sensor electrode when driven for sensing. The corrupting component may be removed either in analog or digitally. In analog, the corrupting component is removed via a tunable capacitance. Digitally, a corrupting component is calculated as an impulse response convolved with the source driver voltage. This corrupting component is then subtracted from a digital value output by the sensing circuitry to obtain a “clean” value.

Claims

1. A processing system configured for simultaneously updating a display and performing capacitive sensing, the processing system comprising:

a source driver configured to drive a source line with a source driver signal during a first time period and to receive resulting signals on a routing trace coupled to a sensor electrode during a second time period that at least partially overlaps with the first time period, the routing trace and the source line being routed proximate each other; and

an interference remover configured to remove source driver effects in the resulting signals that exist due to driving the source line with the source driver signal, by removing an interference signal that is generated based on the source driver signal.

2. The processing system of claim 1, wherein the interference remover is configured to remove the source driver effects by:

subtracting the interference signal from the resulting signal.

3. The processing system of claim 1, wherein:

the interference signal is based on the source driver signal and an impulse response associated with receiver circuitry configured to process the resulting signals.

4. The processing system of claim 3, wherein the interference signal comprises:

the impulse response convolved with the source driver signal.

5. The processing system of claim 1, wherein:

the interference signal is based on the source driver signal, a second source driver signal applied on a second source line, and an impulse response associated with receiver circuitry.

6. The processing system of claim 1, wherein:

the source line and the routing trace are disposed in a common layer.

7. The processing system of claim 1, wherein:

the source line and the routing trace are disposed in separate layers; and

the source line is parallel to the routing trace.

8. The processing system of claim 1, wherein the interference remover includes:

a capacitor.

9. The processing system of claim 8, wherein the interference remover further comprises:

a digital-to-analog converter, configured to scale and negate a voltage associated with the source driver signal to generate a scaled signal, and to apply the scaled signal to the capacitor to generate the interference signal.

10. An input device configured for simultaneously updating a display and performing capacitive sensing, the input device comprising:

a sensor electrode coupled to a routing trace;

a display element coupled to a source line, the source line and the routing trace being routed proximate each other; and

a processing system coupled to the routing trace and the source line, the processing system comprising;

a source driver configured to drive the source line with a source driver signal during a first time period and to receive resulting signals on the routing trace during a second time period that at least partially overlaps with the first time period, and

an interference remover configured to remove source driver effects in the resulting signals that exist due to driving the source line with the source driver signal, by removing an interference signal that is generated based on the source driver signal.

11. The input device of claim 10, wherein the interference remover is configured to remove the source driver effects by:

subtracting the interference signal from the resulting signal.

12. The input device of claim 10, wherein:

the interference signal is based on the source driver signal and an impulse response associated with receiver circuitry configured to process the resulting signals.

13. The input device of claim 12, wherein the interference signal comprises:

the impulse response convolved with the source driver signal.

14. The input device of claim 10, wherein:

the interference signal is based on the source driver signal, a second source driver signal applied on a second source line, and an impulse response associated with receiver circuitry.

15. The input device of claim 10, wherein:

the source line and the routing trace are disposed in a common layer.

16. The input device of claim 10, wherein:

the source line and the routing trace are disposed in separate layers; and

the source line is parallel to the routing trace.

17. The input device of claim 10, wherein the interference remover includes:

a capacitor.

18. The input device of claim 17, wherein the interference remover further comprises:

a digital-to-analog converter, configured to scale and negate a voltage associated with the source driver signal to generate a scaled signal, and to apply the scaled signal to the capacitor to generate the interference signal.

19. A method for simultaneously updating a display and performing capacitive sensing, the method comprising:

driving a source line with a source driver signal during a first time period;

receiving resulting signals on a routing trace coupled to a sensor electrode during a second time period that at least partially overlaps with the first time period, the routing trace and the source line being routed proximate each other; and

removing source driver effects in the resulting signals that exist due to driving the source line with the source driver signal, by removing an interference signal that is generated based on the source driver signal.

20. The method of claim 19, wherein:

the interference signal is based on the source driver signal and an impulse response associated with receiver circuitry configured to process the resulting signals.