Front-end signal compensation

• US 9,323,405 B2
• Filed: 09/30/2013
• Issued: 04/26/2016
• Est. Priority Date: 01/03/2007
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Hotelling, Steve Porter, Land, Brian Richards
• Primary Examiner(s): NGUYEN, JENNIFER T
• Application Number:
  US14/042,462
• Publication Number:
  US 20140028621A1
• Time in Patent Office: 939 Days
• Field of Search: 345/173, 345/174, 345/178, 178/18.06
• US Class Current: 1/1
• 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 2203/04107 Shielding in digitiser, i.e. guard or shielding arrangements, mostly for capacitive touchscreens, e.g. driven shields, driven grounds
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/044 by capacitive means
• 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 touch surface device having improved sensitivity and dynamic range is disclosed. In one embodiment, the touch surface device includes a touch-sensitive panel having at least one sense node for providing an output signal indicative of a touch or no-touch condition on the panel; a compensation circuit, coupled to the at least one sense node, for generating a compensation signal that when summed with the output signal removes an undesired portion of the output signal so as to generated a compensated output signal; and an amplifier having an inverting input coupled to the output of the compensation circuit and a non-inverting input coupled to a known reference voltage.

Claims

1. A touch controller, comprising:

a drive circuit configured for driving a first set of one or more first drive lines of a touch sensor panel with a stimulation signal, and configured for driving a second set of one or more second drive lines of the touch sensor panel with an inversion of the stimulation signal; and

one or more sense circuits configured for receiving one or more compensated touch signals from the touch sensor panel and generating a signal indicative of an amount of touch detected at the touch sensor panel.

2. The touch controller of claim 1, where the drive circuit is configured for driving the first set of drive lines in a sequence while simultaneously driving the second set of second drive lines.

3. The touch controller of claim 1, wherein each of the sense circuits comprises:

an amplifier having an inverting input coupled for receiving the compensated touch signal and a non-inverting input coupled to a known reference voltage; and

a feedback capacitor coupled between an output of the amplifier and the inverting input.

4. The touch controller of claim 1, wherein the touch controller is incorporated into a handheld computing device.

5. A method for generating compensated touch signals, comprising:

driving a first set of one or more first drive lines of a touch sensor panel with a stimulation signal;

driving a second set of one or more second drive lines of the touch sensor panel with an inversion of the stimulation signal;

receiving one or more compensated touch signals from the touch sensor panel; and

generating one or more signals indicative of an amount of touch detected at the touch sensor panel.

6. The method of claim 5, further comprising driving the first set of drive lines in a sequence while simultaneously driving the second set of drive lines.

7. A touch sensor panel, comprising:

one or more first drive lines configured for receiving a stimulation signal from a touch controller;

one or more second drive lines configured for receiving an inversion of the stimulation signal; and

one or more sense lines configured for capacitively coupling with the one or more first drive lines to generate a touch signal on each of the sense lines, and capacitively coupling with the one or more second drive lines to generate a compensation signal on each of the sense lines.

8. The touch sensor panel of claim 7, wherein the one or more sense lines are further configured to render the one or more second drive lines substantially insensitive to touch.

9. The touch sensor panel of claim 7, where each of the sense lines is further configured to sum the touch signal and the compensation signal on that sense line to generate a compensated touch signal on that sense line.

10. The touch sensor panel of claim 7, wherein each of the sense lines is further configured such that an amplitude of the compensation signal on that sense line is selected to be an average of a maximum and minimum amplitude of the touch signal on that sense line, wherein the maximum amplitude corresponds to a detected “

no touch”

condition and the minimum amplitude corresponds to a detected “

max touch”

condition.

11. The touch sensor panel of claim 9, wherein each of the sense lines is further configured such that summing the touch signal and the compensation signal on each sense line substantially removes a static portion of the touch signal to generate the compensated touch signal.

12. The touch sensor panel of claim 8, wherein the one or more sense lines substantially cover the one or more second drive lines.

13. The touch sensor panel of claim 7, incorporated into a handheld computing device.

14. A method of generating compensated touch signals, comprising:

receiving a stimulation signal at one or more first drive lines of a touch sensor panel;

receiving an inversion of the stimulation signal at one or more second drive lines;

capacitively coupling one or more sense lines with the one or more first drive lines to generate a touch signal on each of the sense lines; and

capacitively coupling the one or more sense lines with the one or more second drive lines to generate a compensation signal on each of the sense lines.

15. The method of claim 14, further comprising rendering the one or more second drive lines substantially insensitive to touch.

16. The method of claim 14, further comprising summing the touch signal and the compensation signal on each sense line to generate a compensated touch signal on that sense line.

17. The method of claim 14, further comprising configuring each sense line such that an amplitude of the compensation signal on that sense line is selected to be an average of a maximum and minimum amplitude of the touch signal on that sense line, wherein the maximum amplitude corresponds to a detected “

no touch”

condition and the minimum amplitude corresponds to a detected “

max touch”

condition.

18. The method of claim 16, further comprising substantially removing a static portion of the touch signal by summing the touch signal and the compensation signal on each sense line to generate the compensated touch signal.

19. The method of claim 15, further comprising rendering the one or more second drive lines substantially insensitive to touch by substantially covering the one or more second drive lines with the one or more sense lines.

20. A handheld computing device including a touch sensor panel, the touch sensor panel comprising:

one or more first drive lines configured for receiving a stimulation signal from a touch controller;

one or more second drive lines configured for receiving an inversion of the stimulation signal; and

one or more sense lines configured for capacitively coupling with the one or more first drive lines to generate a touch signal on each of the sense lines, and capacitively coupling with the one or more second drive lines to generate a compensation signal on each of the sense lines.