Panel mismatch compensation for touch enabled displays

• US 10,156,940 B2
• Filed: 03/11/2014
• Issued: 12/18/2018
• Est. Priority Date: 03/11/2014
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Krah, Christoph Horst
• Primary Examiner(s): SIMPSON, LIXI CHOW
• Application Number:
  US14/205,125
• Publication Number:
  US 20150261340A1
• Time in Patent Office: 1,743 Days
• CPC Class Codes: G06F 2203/04104 Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger
• 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 3/04182 Filtering of noise external to the device and not generated by digitiser components
• 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

Abstract

A controller with mismatch compensation for a touch panel is disclosed. A multi-stimulus controller for a touch panel can be formed on a single integrated circuit (single-chip) that can include a transmit section that can generate a plurality of drive signals, a plurality of transmit channels that can transmit the drive signals simultaneously to drive the touch panel, a receive channel that can receive a sense signal resulting from the driving of the touch panel, and a demodulation section that can demodulate the received sense signal to obtain sensing results, the demodulation section including a demodulator and a vector operator. The transmit section can include a pair of adjustable gain buffers that can adjust the gain of stimulation signals to account for the signal path length mismatch of various transmit signal paths.

Claims

1. A controller for a touch sensor panel, the controller comprising:

transmit circuitry configured to generates a plurality of drive signals;

a plurality of transmit channels configured to transmit the plurality of drive signals simultaneously to drive the touch sensor panel; and

a plurality of adjustable gain buffers coupled to the transmit circuitry, wherein the plurality of adjustable gain buffers are directly connected to a plurality of outputs of at least one digital-to-analog converter (DAC), wherein gain of one or more of the plurality of adjustable gain buffers is adjustable to adjust an amplitude of one or more of the plurality of drive signals, thereby compensating the plurality of drive signals from the transmit circuitry for differences in path lengths in the touch sensor panel.

2. The controller of claim 1, further comprising:

one or more receive channels configured to receive sense signals resulting from the driving of the touch sensor panel; and

sense circuitry coupled to the one or more receive channels and configurable to detect changes in the sense signals on the one or more receive channels;

wherein the path lengths include signal paths from the plurality of transmit channels to the one or more receive channels.

3. The controller of claim 1, wherein at least one of the plurality of adjustable gain buffers amplifies at least one of the plurality of drive signals by at least one amplification factor, and wherein a magnitude of the at least one amplification factor for the at least one of the plurality of adjustable gain buffers is different from a magnitude of another amplification factor for at least another of the plurality of adjustable gain buffers.

4. The controller of claim 1, wherein the plurality of adjustable gain buffers comprises a first adjustable gain buffer and a second adjustable gain buffer, the first adjustable gain buffer directly connected to a positive phase output of the at least one DAC and the second adjustable gain buffer directly connected to a negative phase output of the at least one DAC.

5. The controller of claim 1, wherein at least one of the plurality of adjustable gain buffers amplifies at least one of the plurality of drive signals by at least one amplification factor, and

wherein the at least one amplification factor for the at least one of the plurality of adjustable gain buffers is selected based on a scan step, each scan step associated with compensation gains for a given phase configuration.

6. The controller of claim 5, wherein a plurality of amplification factors for the plurality of adjustable gain buffers is stored in transmit logic, the transmit logic coupled to the plurality of adjustable gain buffers.

7. A controller for a touch sensor panel, the controller comprising:

transmit circuitry configured to generates a plurality of drive signals;

a plurality of transmit channels that transmit the plurality of drive signals simultaneously to drive the touch sensor panel; and

a plurality of adjustable gain buffers coupled to the transmit circuitry, wherein gain of one or more of the plurality of adjustable gain buffers is adjustable to adjust an amplitude of one or more of the plurality of drive signals, thereby compensating the plurality of drive signals from the transmit circuitry for differences in path lengths in the touch sensor panel,

wherein at least one of the plurality of adjustable gain buffers amplifies at least one of the plurality of drive signals by at least one amplification factor, and wherein a magnitude of the at least one amplification factor for the at least one of the plurality of adjustable gain buffers is different from a magnitude of another amplification factor for at least another of the plurality of adjustable gain buffers.

8. The controller of claim 7, further comprising:

one or more receive channels configured to receive sense signals resulting from the driving of the touch sensor panel; and

sense circuitry coupled to the one or more receive channels and configurable to detect changes in the sense signals on the one or more receive channels;

wherein the path lengths include signal paths from the plurality of transmit channels to the one or more receive channels.

9. The controller of claim 7, wherein the plurality of adjustable gain buffers are directly connected to a plurality of outputs of at least one digital-to-analog converter (DAC).

10. The controller of claim 9, wherein the plurality of adjustable gain buffers comprises a first adjustable gain buffer and a second adjustable gain buffer, the first adjustable gain buffer directly connected to a positive phase output of the at least one DAC and the second adjustable gain buffer directly connected to a negative phase output of the at least one DAC.

11. The controller of claim 7, wherein the at least one amplification factor for the at least one of the plurality of adjustable gain buffers is selected based on a scan step, each scan step associated with compensation gains for a given phase configuration.

12. The controller of claim 11, wherein a plurality of amplification factors for the plurality of adjustable gain buffers is stored in transmit logic, the transmit logic coupled to the plurality of adjustable gain buffers.

13. A method for generating stimulation signals for a touch sensor panel, the method comprising:

generating a plurality of drive signals; and

compensating the plurality of drive signals using a plurality of adjustable gain buffers, wherein gain of one or more of the plurality of adjustable gain buffers is adjustable to adjust an amplitude of one or more of the plurality of drive signals, wherein compensating the plurality of drive signals comprises configuring at least one of the plurality of adjustable gain buffers to amplify at least one of the plurality of drive signals by at least one amplification factor, wherein a magnitude of the at least one amplification factor for the at least one of the plurality of adjustable gain buffers is different from a magnitude of another amplification factor for at least another of the plurality of adjustable gain buffers.

14. The method of claim 13, wherein compensating the plurality of drive signals comprises:

adjusting the at least one amplification factor for the at least one of the plurality of adjustable gain buffers based on a scan step, each scan step associated with compensation gains for a given phase configuration.

15. The method of claim 14, wherein compensating the plurality of drive signals further comprises:

receiving the at least one amplification factor at the at least one of the adjustable gain buffers.

16. A method for generating a plurality of amplification factors for a plurality of adjustable gain buffers in a touch sensor panel, the method comprising:

generating a plurality of drive signals when no touch event occurs at the touch sensor panel;

sensing at one or more receive channels a total charge at an input to one or more sense amplifiers coupled to the one or more receive channels; and

selecting an amplification factor for gain of at least one of the plurality of adjustable gain buffers, wherein;

the gain is adjustable to adjust an amplitude of at least one of the plurality of drive signals,

the amplification factor corresponds to the gain resulting in a minimum total charge sensed on the one or more receive channels, and

the amplification factor for the at least one of the plurality of adjustable gain buffers is different from another amplification factor for at least another of the plurality of adjustable gain buffers.

17. The method of claim 16, wherein:

selecting the amplification factor comprises selecting one or more amplification factors for one or more gains of one or more of the plurality of adjustable gain buffers for a plurality of scan steps, each scan step associated with compensation gains for a given phase configuration.

18. A non-transitory computer readable storage medium having stored thereon a set of instructions for generating a plurality of amplification factors for a plurality of adjustable gain buffers in a touch sensor panel, that when executed by a processor causes the processor to:

generate a plurality of drive signals when no touch event occurs at the touch sensor panel;

sense at one or more receive channels a total charge at an input to one or more sense amplifiers coupled to the one or more receive channels; and

select an amplification factor for gain of at least one of the plurality of adjustable gain buffers, wherein;

the gain is adjustable to adjust an amplitude of at least one of the plurality of drive signals,

the amplification factor corresponds to the gain resulting in a minimum total charge sensed on the one or more receive channels, and

the amplification factor for the at least one of the plurality of adjustable gain buffers is different from another amplification factor for at least another of the plurality of adjustable gain buffers.

19. The non-transitory computer readable storage medium of claim 18, wherein the processor selects one or more amplification factors for one or more gains of one or more of the plurality of adjustable gain buffers for a plurality of scan steps, each scan step associated with compensation gains for a given phase configuration.

20. A non-transitory computer readable storage medium having stored thereon a set of instructions for generating stimulation signals for a touch sensor panel, that when executed by a processor causes the processor to:

generate a plurality of drive signals; and

compensate the plurality of drive signals using a plurality of adjustable gain buffers, wherein gain of one or more of the plurality of adjustable gain buffers is adjustable to adjust an amplitude of one or more of plurality of drive signals;

wherein the processor configures at least one of the plurality of adjustable gain buffers to amplify at least one of the plurality of drive signals by at least one amplification factor, wherein a magnitude of the at least one amplification factor for the at least one of the plurality of adjustable gain buffers is different from a magnitude of another amplification factor for at least another of the plurality of adjustable gain buffers.

21. The non-transitory computer readable storage medium of claim 20, wherein the processor adjusts the at least one amplification factor for the at least one of the plurality of adjustable gain buffers based on a scan step, each scan step associated with compensation gains for a given phase configuration.

22. The non-transitory computer readable storage medium of claim 21, wherein the processor supplies the at least one amplification factor to the at least one of the adjustable gain buffers.