Flexible timing and multiplexing for a display device comprising an integrated capacitive sensing device

• US 9,176,621 B2
• Filed: 09/24/2012
• Issued: 11/03/2015
• Est. Priority Date: 11/18/2011
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Lillie, Jeffrey S., Knausz, Imre, Ozbas, Murat
• Primary Examiner(s): Yodichkas, Aneeta
• Assistant Examiner(s): Castiaux, Brent D
• Application Number:
  US13/625,031
• Publication Number:
  US 20130127779A1
• Time in Patent Office: 1,135 Days
• Field of Search: 345173-215
• US Class Current: 1/1
• 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 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

Embodiments of the invention generally provide an input device that simultaneously transmits a multiplexed signal across two or more transmitter electrodes used in touch detection. The multiplexed includes two or more component signals that are transmitted on respective electrodes (or channels). The component signals are then decoded and correlated to indicate a positional location of an input object. Various multiplexing schemas—e.g., code division multiplexing, frequency division multiplexing, orthogonal frequency division multiplexing, and the like—may be used to generate the multiplex signal and then demultiplex the received results.

Claims

1. A processing system coupled to transmitter electrodes and receiver electrodes, the processing system comprising:

a driver module coupled to the transmitter electrodes, each of the transmitter electrodes comprising one or more common electrodes configured for display updating and touch detection,

wherein the driver module is configured to simultaneously drive a first one of the transmitter electrodes with a first signal and second one of the transmitter electrodes with a second signal, wherein the first signal and the second signal are based on different codes of a plurality of distinct digital codes, wherein each of the distinct digital codes is substantially mathematically independent from each other, and wherein the driver module is configured to drive the first and second signals when display updating is inactive;

a polarity shifter configured to selectively invert the first signal relative to the second signal during a first time period;

a receiver module coupled to the receiver electrodes, the receiver module configured to receive, using the receiver electrodes, resulting signals based on the first and second signals; and

a determination module configured to generate demodulated output signals by demodulating the resulting signals based on the distinct digital codes and to determine positional information for an input object at least partially based on the demodulated output signals.

2. The processing system of claim 1, wherein the distinct digital codes are part of a code division multiplexing schema.

3. The processing system of claim 1, wherein the first and second signals are the same frequency, wherein the first signal is phase shifted relative to the second signal.

4. The processing system of claim 1, wherein the polarity shifter is configured to selectively invert the second signal relative to the first signal during a second time period subsequent to the first time period.

5. The processing system of claim 1, wherein driving the first and second signals simultaneously increases the signal to noise ratio relative to transmitting only one of the first and second signals individually.

6. The processing system of claim 1, wherein the driver module drives the first signal and the second signal by generating a plurality of control signals used to activate logic circuitry.

7. The processing system of claim 1, wherein the driver module is configured to generate the first and second signals by switching between a first and a second voltage potential.

8. The processing system of claim 7, wherein the first voltage potential is a common voltage of a display device used when updating the display screen.

9. A display device having an integrated capacitive sensing device, the display device comprising:

receiver electrodes;

transmitter electrodes, each of the transmitter electrodes comprising one or more common electrodes configured for display updating and touch detection;

logic circuitry disposed on a substrate comprising the transmitter electrodes;

a processor coupled to the transmitter electrodes via the logic circuitry, wherein, during a first period, the processor is configured to transmit control signals to the logic circuitry to simultaneously drive a first one of the transmitter electrodes with a first signal and second one of the transmitter electrodes with a second signal, wherein the first signal and the second signal are based on different codes of a plurality of distinct digital codes, wherein each of the distinct digital codes is substantially mathematically independent from each other, and wherein the processor is configured to drive the first and second signals when display updating is inactive,

wherein the logic circuitry comprises switching logic that generates the first and second signals by switching between a first and a second voltage potentials based on at least one of the control signals, and wherein the processor drives a polarity signal, wherein the switching logic is configured to invert the first signal relative to the second signal during a first time period based on the polarity signal;

wherein the processor is coupled to the receiver electrodes and configured to receive, using the receiver electrodes, resulting signals based on the first and second signals during the first period,

wherein the processor is configured to generate demodulated output signals by demodulating the resulting signals based on the distinct digital codes and to determine positional information for an input object at least partially based on the demodulated output signals.

10. The display device of claim 9, wherein the logic circuitry comprises a first plurality of cascaded memory elements, wherein each of the first plurality of memory elements selects a group of at least two transmitter electrodes for performing touch detection.

11. The display device of claim 10, wherein the logic circuitry comprises a second plurality of cascaded memory elements, wherein each of the second plurality of memory elements selects a group of at least two of the common electrodes when updating a display screen in the display device.

12. The display device of claim 10, wherein the first plurality of cascaded memory elements is a shift register.

13. The display device of claim 9, wherein the switching logic is configured to invert the second signal relative to the first signal during a second time period subsequent to the first time period based on the polarity signal.

14. The display device of claim 9, wherein the processor is mounted on the substrate and the receiver electrodes are disposed on the substrate.

15. A method for performing touch detection, the method comprising:

transmitting simultaneously a first transmitter signal on a first transmitter electrode and a second transmitter signal on a second transmitter electrode, wherein each of the transmitter electrodes comprises one or more common electrodes configured for both updating displayed information in a display screen and performing touch detection,

wherein the first and second transmitter signals are respective channels of a multiplexed signal generated according to a multiplexing schema, and wherein the first and second transmitter signals are transmitted when display updating is inactive, and wherein a polarity signal inverts the first signal relative to the second signal during a first time period;

receiving a first resulting signal on a first receiver electrode based on the first transmitter signal and a second resulting signal on a second receiver electrode based on the second transmitter signal;

demultiplexing the first and second resulting signals; and

determining positional information for an input object at least partially based on the demultiplexed signals.

16. The method of claim 15, wherein the multiplexing schema is one of:

code division multiplexing and frequency division multiplexing.

17. The method of claim 15, wherein the first and second transmitter signals are orthogonal.

18. The method of claim 15, wherein the polarity signal inverts the second signal relative to the first signal during a second time period subsequent to the first time period.