Charge recycling for multi-touch controllers

• US 8,432,364 B2
• Filed: 02/25/2008
• Issued: 04/30/2013
• Est. Priority Date: 02/25/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Krah, Christoph Horst
• Primary Examiner(s): Amadiz, Rodney
• Application Number:
  US12/037,001
• Publication Number:
  US 20090212642A1
• Time in Patent Office: 1,891 Days
• Field of Search: 345 94-101, 345173-178, 178 1801- 1811, 178 2001- 2004
• US Class Current: 345/173
• CPC Class Codes: G06F 1/3203 Power management, i.e. event-based initiation of a power-saving mode
• CPC Class Codes: G06F 1/3262 Power saving in digitizer or tablet
• 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: H03K 19/0019 by energy recovery or adiabatic operation
• CPC Class Codes: H03K 7/08 Duration or width modulation ; Duty cycle modulation

Abstract

The recycling of charge when two or more of the drive lines of a touch sensor panel are being simultaneously stimulated with the in-phase and anti-phase components of a stimulation signal is disclosed. To perform charge recycling, a discharge path can be selectively formed between drive lines being stimulated with the in-phase and anti-phase components of the stimulation signal. A multiplexer can be coupled to the driver of each drive line and the common discharge path. When charge recycling is to be performed, control logic can configure the multiplexers to isolate the driver and connect the drive lines being stimulated with the in-phase component of the stimulation signal with the drive lines being stimulated with the anti-phase component of the stimulation signal. The capacitance on the charged-up drive lines can then discharge to the capacitance on the discharged drive lines.

Claims

1. An apparatus for recycling charge during stimulation of a touch sensor panel, comprising:

a plurality of drivers coupled to a first group of one or more drive lines of the touch sensor panel and a second group of one or more drive lines of the touch sensor panel, the plurality of drivers configured for simultaneously driving the first and second groups with stimulation signals;

a plurality of first multiplexers coupled to the first and second groups and configurable for providing a first charge recycling path for the first and second groups, the first charge recycling path for recycling charge stored in capacitances on the drive lines of the first and second groups.

2. The apparatus of claim 1, the plurality of drivers further configured for simultaneously driving the first and second groups with stimulation signals of opposite polarity, and the plurality of first multiplexers further configurable for providing the first charge recycling path between the first and second groups for recycling charge between the first and second groups.

3. The apparatus of claim 2, further comprising control logic coupled to the plurality of multiplexers for configuring the multiplexers to partially discharge a first capacitance formed at the first group through the first charge recycling path while simultaneously partially charging a second capacitance formed at the second group.

4. The apparatus of claim 3, further comprising:

a charge recycling switch coupled between each driver and a holding capacitor; and

a ground switch coupled between each driver and ground;

wherein the control logic is further coupled to the charge recycling switches and ground switches for configuring both sets of switches to recycle charge into the holding capacitor when a capacitance formed at an output of the driver is discharged through the driver.

5. The apparatus of claim 3, the control logic comprising a charge recycling modulation block for configuring the multiplexers using a pulse width modulated (PWM) control signal to regulate the discharging of the first capacitance and the charging of the second capacitance.

6. The apparatus of claim 2, the plurality of first multiplexers further configurable for providing a second charge recycling path between a third group of one or more drive lines and a fourth group of one or more drive lines, the second charge recycling path for recycling charge between the third and fourth groups.

7. The apparatus of claim 2, further comprising a touch sensor panel including the first and second groups of one or more drive lines, and wherein the plurality of drivers, the plurality of multiplexers, and the touch sensor panel are incorporated within a computing system.

8. The apparatus of claim 7, wherein the computing system is incorporated within a mobile telephone.

9. The apparatus of claim 7, wherein the computing system is incorporated within a media player.

10. The apparatus of claim 7, wherein the computing system is incorporated within a personal computer.

11. The apparatus of claim 1, the plurality of drivers further configured for simultaneously driving the first and second groups with stimulation signals of a same frequency and phase, and the plurality of first multiplexers further configurable for providing the first charge recycling path from the first and second groups to a holding capacitor.

12. The apparatus of claim 11, further comprising control logic coupled to the plurality of multiplexers for configuring the multiplexers to partially discharge the charge stored in the capacitances on the drive lines of the first and second groups through the first charge recycling path and into the holding capacitor, and for configuring the multiplexers to partially charge the capacitances on the drive lines of the first and second groups through the first charge recycling path with charge stored in the holding capacitor.

13. The apparatus of claim 1, further comprising control logic coupled to the plurality of multiplexers for selectively configuring the multiplexers to recycle the charge stored in the capacitances on the drive lines of the first and second groups according to whether a regular panel scan or an auto-scan is to be performed.

14. A method for recycling charge during stimulation of a touch sensor panel, comprising:

simultaneously driving a first group of one or more drive lines of the touch sensor panel and a second group of one or more drive lines of the touch sensor panel with stimulation signals;

providing a first charge recycling path for the first and second groups, the first charge recycling path for recycling charge stored in capacitances on the drive lines of the first and second groups.

15. The method of claim 14, further comprising simultaneously driving the first and second groups with stimulation signals of opposite polarity, and providing the first charge recycling path between the first and second groups for recycling charge between the first and second groups.

16. The method of claim 15, further comprising partially discharging a first capacitance formed at the first group through the first charge recycling path while simultaneously partially charging a second capacitance formed at the second group by transferring charge from the first capacitance to the second capacitance.

17. The method of claim 16, further comprising discharging the first capacitance and charging the second capacitance by configuring a driver logic connected to the first group to provide a discharge path to a holding capacitor to recycle charge into the holding capacitor.

18. The method of claim 16, further comprising using a pulse width modulated (PWM) control signal to regulate the discharging of the first capacitance and the charging of the second capacitance.

19. The method of claim 15, further comprising providing a second charge recycling path between a third group of one or more drive lines and a fourth group of one or more drive lines, the second charge recycling path for recycling charge between the third and fourth groups.

20. The method of claim 19, further comprising partially discharging a third capacitance formed at the third group through the second charge recycling path while simultaneously partially charging a fourth capacitance formed at the fourth group by transferring charge from the third capacitance to the fourth capacitance.

21. The method of claim 14, further comprising simultaneously driving the first and second groups with stimulation signals of a same frequency and phase, and providing a first discharge path from the first and second groups to a holding capacitor.

22. The method of claim 21, further comprising partially discharging the charge stored in the capacitances on the drive lines of the first and second groups through the first charge recycling path and into the holding capacitor, and partially charging the capacitances on the drive lines of the first and second groups through the first charge recycling path with charge stored in the holding capacitor.

23. The method of claim 14, further comprising selectively recycling the charge stored in the capacitances on the drive lines of the first and second groups according to whether a regular panel scan or an auto-scan is to be performed.

24. A digital media player including an apparatus for recycling charge during stimulation of a touch sensor panel, the apparatus comprising:

a plurality of drivers coupled to a first group of one or more drive lines of the touch sensor panel and a second group of one or more drive lines of the touch sensor panel, the plurality of drivers configured for simultaneously driving the first and second groups with stimulation signals; and

a plurality of first multiplexers coupled to the first and second groups and configurable for providing a first charge recycling path for the first and second groups, the first charge recycling path for recycling charge stored in capacitances on the drive lines of the first and second groups.

25. A personal computer including an apparatus for recycling charge during stimulation of a touch sensor panel, the apparatus comprising:

a plurality of drivers coupled to a first group of one or more drive lines of the touch sensor panel and a second group of one or more drive lines of the touch sensor panel, the plurality of drivers configured for simultaneously driving the first and second groups with stimulation signals; and

a plurality of first multiplexers coupled to the first and second groups and configurable for providing a first charge recycling path for the first and second groups, the first charge recycling path for recycling charge stored in capacitances on the drive lines of the first and second groups.