Method and apparatus for improved input sensing using a display processor reference signal

• US 8,970,546 B2
• Filed: 08/31/2012
• Issued: 03/03/2015
• Est. Priority Date: 08/31/2012
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Schwartz, Adam, Reynolds, Joseph Kurth
• Primary Examiner(s): Cheng, Joe H
• Application Number:
  US13/602,049
• Publication Number:
  US 20140062937A1
• Time in Patent Office: 914 Days
• Field of Search: 345/156, 345/173, 345/174, 345/179, 345/204, 178/18.06
• US Class Current: 345/174
• CPC Class Codes: G06F 2203/04108 Touchless 2D- digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus, also when it does not touch, but is proximate to the digitiser's interaction surface without distance measurement in the Z direction
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• 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 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer

Abstract

Embodiments of the invention generally provide a method and apparatus that is configured to reduce the effects of interference that is undesirably provided to a transmitter signal that is delivered from a transmitter signal generating device to a sensor processor to determine if an input object is disposed within a touch sensing region of a touch sensing device. In one embodiment, the sensor processor includes a receiver channel that has circuitry that is configured to separately receive a transmitter signal delivered from a display processor and a sensor processor reference signal that is based on a display processor reference signal to reliably sense the presence of an object. Embodiments of the invention described herein thus provide an improved apparatus and method for reliably sensing the presence of an object by a touch sensing device.

Claims

1. An input device, comprising:

a plurality of transmitter electrodes comprising a plurality of common electrodes configured to operate in a first mode for capacitive sensing and configured to operate in a second mode for updating a display device;

a plurality of receiver electrodes;

a display processor coupled to the plurality of transmitter electrodes and configured to drive at least one of the transmitter electrodes with a transmitter signal for capacitive sensing; and

a sensor processor coupled to the plurality of receiver electrodes and configured to receive resulting signals with the plurality of receiver electrodes when at least one of the common electrodes are driven for capacitive sensing, wherein the sensor processor comprises one or more receiver channels, and wherein each of the one or more receiver channels is coupled to a receiver electrode of the plurality of receiver electrodes, and each of the one or more receiver channels have;

a first receiver channel input port configured to receive at least a portion of the resulting signals; and

a second receiver channel input port configured to receive a sensor processor reference signal that is based on a display processor reference signal,

wherein each of the one or more receiver channels is configured to provide an output signal based on a comparison of the at least a portion of the resulting signals and the sensor processor reference signal.

2. The input device of claim 1, wherein each of the one or more receiver channels comprises a charge accumulator, wherein the second receiver channel input port is coupled to a reference input of the charge accumulator.

3. The input device of claim 1, wherein the display processor reference signal is configured to be electrically coupled to a ground of the sensor processor.

4. The input device of claim 1, wherein the sensor processor further comprises a reference channel configured to provide a reference channel output wherein the reference channel has a first reference channel input port that is configured to receive a reference channel input signal and a second reference channel input port that is in electrical communication with the second receiver channel input port and is configured to receive the sensor processor reference signal.

5. The input device of claim 4, wherein the sensor processor reference signal is based on at least one of the display processor reference signal and a second display processor reference signal.

6. The input device of claim 4, wherein the reference channel input signal is based on at least one of the display processor reference signal and a second display processor reference signal.

7. The input device of claim 4, wherein the reference channel input signal is based on the transmitter signal.

8. The input device of claim 7, wherein the transmitter signal is generated from a level shifter that translates a sensor processor transmitter signal into voltage levels based on at least one of the display processor reference signal and a second display processor reference signal.

9. A sensor processor for an input device, comprising:

a sensor circuitry coupled to a plurality of sensor electrodes, wherein the sensor processor is coupled to a display processor that is configured to drive a plurality of common electrodes for updating a display device, wherein the sensor processor comprises at least one receiver channel configured to receive resulting signals with at least one of the plurality of sensor electrodes and to receive a sensor processor reference signal that is based on a display processor reference signal, and wherein the receiver channel is further configured to provide an receiver channel output signal based on at least a portion of the received resulting signals and the sensor processor reference signal.

10. The sensor processor of claim 9, wherein the display processor reference signal is configured to be electrically coupled to a ground of the sensor processor.

11. The sensor processor of claim 9, wherein the sensor processor further comprises:

a reference channel that is configured to provide a reference channel output signal, wherein the reference channel is configured to receive a first signal based on the first display processor reference signal and wherein an output of the sensor processor is based on the receiver channel output signal and the reference channel output signal.

12. The sensor processor of claim 11, wherein the reference channel is further configured to receive a second signal based on a second display processor reference signal.

13. The sensor processor of claim 11, wherein the receiver channel is configured to provide the receiver channel output signal to an analog-to-digital converter and wherein the reference channel is configured to provide the reference channel output signal to the analog-to-digital converter, and wherein the output of the sensor processor that is based on the receiver channel output signal and the reference channel output signal comprises the output of the sensor processor being based on an output of the analog-to-digital converter.

14. The sensor processor of claim 9, wherein the display processor is further configured to drive the common electrodes for capacitive sensing comprising transmitting a transmitter signal with at least one of the common electrodes, and wherein the sensor processor comprises a reference channel that is configured to receive at least a portion of the transmitter signal and the sensor processor reference signal.

15. The sensor processor of claim 9, wherein the sensor processor further comprises a reference channel that has a first reference channel input port that is configured to receive a reference channel input signal and a second reference channel input port that is in electrical communication with the second receiver channel input port and is configured to receive the sensor processor reference signal, wherein the reference channel input signal is based on a transmitter signal that is generated from a level shifter that translates a sensor processor transmitter signal into voltage levels based on at least one of the display processor reference signal and a second display processor reference signal.

16. The sensor processor of claim 9, wherein the display processor is further configured to drive the plurality of common electrodes for capacitive sensing and wherein receiving resulting signals with the plurality of sensor electrodes comprises receiving resulting signals when the display processor drives the plurality of common electrodes for capacitive sensing.

17. The sensor processor of claim 9, wherein the sensor processor is further configured to drive the plurality of sensor electrodes for capacitive sensing, and wherein receiving resulting signals with the plurality of sensor electrodes comprises receiving the resulting signals with the plurality of sensor electrodes when the sensor processor drives the plurality of sensor electrodes for capacitive sensing.

18. A processing system for an input device, the processing system comprising:

a display processor configured to drive a plurality of common electrodes for updating a display device, the display processor comprising a display processor reference signal,

a sensor processor configured to receive resulting signals from a plurality of sensor electrodes, wherein the sensor processor comprises a first reference channel configured to generate a first reference channel output signal at least partially based on the display processor reference signal, wherein the processing system is configured to determine positional information for an input object in a sensing region of the input device at least based in part on the resulting signals and the first reference channel output signal.

19. The processing system of claim 18, wherein the display processor is further configured to drive the plurality of common electrodes for capacitive sensing comprising driving at least one of the plurality of common electrodes with a transmitter signal, wherein receiving resulting signals from a plurality of sensor electrodes comprises receiving a resulting signal when at least one of the plurality of common electrodes are driven with a transmitter signal, and wherein the first reference channel output signal is further generated based on the transmitter signal.

20. A processing system for an input device of claim 19, wherein the first reference channel is further configured to receive a first reference channel input signal based on at least part of the transmitter signal and the display processor reference signal.

21. The display processor of claim 20, wherein receiving the first reference channel input signal based on at least part of the transmitter signal wherein the transmitter signal is generated from a level shifter that translates a sensor processor transmitter signal into voltage levels based on at least one of the display processor reference signal and a second display processor reference signal.

22. The processing system of claim 18, wherein the display processor is further configured to drive the plurality of common electrodes for capacitive sensing comprising driving at least one of the plurality of common electrodes with a transmitter signal, wherein the transmitter signal comprises a waveform that transitions from a first voltage potential to a second voltage potential, wherein receiving resulting signals from a plurality of sensor electrodes comprises receiving a resulting signal when at least one of the plurality of common electrodes are driven with a transmitter signal, and wherein the first reference channel output signal is further generated based on a modulated signal that is based on the first voltage potential.

23. The processing system of claim 18, wherein the first reference channel is further configured to receive a first reference channel input signal based on at least part of a transmitter signal and a second reference channel input signal that is based on the display processor reference signal.

24. The processing system of claim 18, wherein the sensor processor comprises one or more receiver channels, and wherein each of the one or more receiver channels is coupled to a sensor electrode of the plurality of sensor electrodes, and each of the one or more receiver channels has:

a first receiver channel input port configured to receive at least a portion of the resulting signals; and

a second receiver channel input port configured to receive a sensor processor reference signal that is based in part on the display processor reference signal,

wherein each of the one or more receiver channels is configured to provide a receiver channel output signal based on a comparison of the signals received at the first receiver channel input port and the second receiver channel input port.

25. The processing system of claim 18, wherein the display processor reference signal is configured to be electrically coupled to a system ground of the sensor processor.

26. The processing system of claim 18, wherein the first reference channel is further configured to receive a first reference channel input signal that is based on a transmitter signal that is generated from a level shifter that translates a sensor processor transmitter signal into voltage levels based on at least one of the display processor reference signal and a second display processor reference signal.

27. The processing system of claim 18, wherein the sensor processor is further configured to drive the plurality of sensor electrodes for capacitive sensing, and wherein receiving the resulting signals from the plurality of sensor electrodes comprises receiving the resulting signals from the plurality of sensor electrodes when the plurality of sensor electrodes are driven for capacitive sensing.

28. The processing system of claim 27, wherein driving the plurality of sensor electrodes for capacitive sensing comprises driving the plurality of sensor electrodes with a signal comprising a waveform that transitions from a first voltage potential to a second voltage potential, and wherein the first reference channel is configured to receive a generated modulated signal that is based on the first voltage potential.

29. A method of sensing an input object in a sensing region of an input device, comprising:

driving a display update on at least one of a plurality of common electrodes, the common electrodes configured for capacitive sensing and updating a display device;

driving a transmitter signal onto at least one of a plurality of common electrodes;

receiving a resulting signal from one or more receiver electrodes, wherein the resulting signal comprises effects corresponding to the transmitter signal; and

comparing the resulting signal with a sensor processor reference signal that is based on a display processor reference signal.

30. The method of claim 29, wherein comparing the resulting signal with the sensor processor reference signal further comprises:

providing the resulting signal to a first input of a charge accumulator; and

providing the sensor processor reference signal to a second input of the charge accumulator, wherein the charge accumulator is configured to;

form a receiver channel output signal using the resulting signal and the sensor processor reference signal; and

output the receiver channel output signal to a host system for sensing the presence of an object near the one or more receiver electrodes.

31. The method of claim 29, wherein comparing the resulting signal with the sensor processor reference signal further comprises:

providing the resulting signal to a receiver channel;

providing the display processor reference signal to a reference channel; and

comparing the output of the receiver channel to the output of the reference channel.

32. The method of claim 31, further comprising:

outputting the receiver channel output signal to a host system to provide data for sensing the input object in the sensing region of the input device.

33. The method of claim 29, wherein driving the transmitter signal is provided by a display processor, and driving of the transmitter signal is based on a communication signal provided by a sensor processor, said sensor processor coupled to the one or more receiver electrodes, wherein the method further comprises:

level shifting the communication signal, wherein level shifting comprises;

receiving the communication signal; and

adjusting the voltage level of the received communication signal to form an adjusted communication signal; and

delivering the adjusted communication signal to the display processor or a reference channel disposed in the sensor processor.