Reconfigurable circuit topology for both self-capacitance and mutual capacitance sensing

• US 9,933,879 B2
• Filed: 11/25/2013
• Issued: 04/03/2018
• Est. Priority Date: 11/25/2013
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Yao, Weijun, Brahma, Kingsuk, Syed, Taif A.
• Primary Examiner(s): Flores, Roberto
• Application Number:
  US14/089,418
• Publication Number:
  US 20150145802A1
• Time in Patent Office: 1,590 Days
• CPC Class Codes: G06F 2203/04106 Multi-sensing digitiser, i.e. digitiser using at least two different sensing technologies simultaneously or alternatively, e.g. for detecting pen and finger, for saving power or for improving position detection
• CPC Class Codes: G06F 3/041662 using alternate mutual and self-capacitive scanning
• 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 sensor panel configured to switch between a mutual capacitance touch sensing architecture and a self-capacitance touch sensing architecture is provided. The touch sensor panel includes circuitry that can switch the configuration of touch electrodes to act as either drive lines in a mutual capacitance configuration or as sense electrodes in a self-capacitance configuration. The touch sensor panel also includes circuitry that can switch the configuration of touch electrodes to act as either sense lines in a mutual capacitance configuration or as sense electrode in a self-capacitance configuration. By splitting a self-capacitance touch mode into a drive line self-capacitive mode and sense line self-capacitive mode, the touch sensor panel is able to reuse components thus requiring less space, weight and power.

Claims

1. A method for switchably operating a touch sensor panel in a self-capacitance mode and a mutual capacitance mode, the method comprising:

in the mutual capacitance mode;

configuring a first set of multiple lines as drive lines in a mutual capacitance configuration;

configuring a second set of multiple lines as sense lines in the mutual capacitance configuration; and

uncoupling the first set of multiple lines and the second set of multiple lines from a shield buffer and coupling an input of the shield buffer to a reference voltage; and

in the self-capacitance mode;

configuring the first set of multiple lines as sense electrodes in a self-capacitance configuration;

uncoupling the second set of multiple lines from a sense amplifier;

coupling the second set of multiple lines to a shield buffer and coupling the input of the shield buffer to a shield voltage, different from the reference voltage;

coupling the first set of multiple lines with the sense amplifier;

configuring the second set of multiple lines as sense electrodes in the self-capacitance configuration;

uncoupling the first set of multiple lines from the sense amplifier;

coupling the first set of multiple lines to a shield buffer and coupling the input of the shield buffer to the shield voltage; and

coupling the second set of multiple lines with the sense amplifier.

2. The method of claim 1, wherein configuring the first set of multiple lines as drive lines comprises coupling one or more stimulation sources to the first set of multiple lines.

3. The method of claim 1, wherein configuring the first set and the second set of multiple lines as sense electrodes comprises coupling a set of sensing circuits to the first set and the second set of multiple lines.

4. The method of claim 3, wherein the sensing circuitry used to configure the first set of multiple lines as sense electrodes is the same sensing circuitry used to configure the second set of multiple lines as sense electrodes.

5. The method of claim 3, wherein the sensing circuitry is connected to a DC voltage source during the mutual capacitance mode and to an AC voltage source during the self-capacitance mode.

6. The method of claim 1 further comprising:

configuring the first set of multiples lines to be connected to a voltage source while sensing the second set of multiple lines; and

configuring the second set of multiple lines to be connected to the voltage source while sensing the first set of multiple lines.

7. The method of claim 6, wherein the voltage source produces a signal having substantially the same frequency and phase as a stimulation signal used to sense the first set of multiple lines and the second set of multiple lines.

8. The method of claim 7, wherein the voltage source is also used to stimulate the first set of multiple lines while sensing the first set of multiple lines and to stimulate the second set of multiple lines while sensing the second set of multiple lines.

9. The method of claim 1, further comprising switchably coupling an input of the sense amplifier to a first line of the first set of multiple lines and to a second line of the second set of multiple lines.

10. A touch sensitive device capable of operating in both a self-capacitance and a mutual capacitance mode, the device comprising:

a touch sensor panel, the touch sensor panel including both a first set of multiple lines and a second set of multiple lines;

switching circuitry coupled to both the first set of multiple lines and the second set of multiple lines;

a sense amplifier; and

a processor capable of;

in the mutual capacitance mode;

configuring the first set of multiple lines as drive lines in a mutual capacitance configuration; and

configuring the second set of multiple lines as sense lines in the mutual capacitance configuration; and

uncoupling the first set of multiple lines and the second set of multiple lines from a shield buffer and coupling an input of the shield buffer to a reference voltage; and

in the self-capacitance mode;

configuring the first set of multiple lines as sense electrodes in a self-capacitance configuration;

uncoupling the second set of multiple lines from the sense amplifier;

coupling the second set of multiple lines to a shield buffer and coupling the input of the shield buffer to a shield voltage, different from the reference voltage;

coupling the sense amplifier with the first set of multiple lines;

configuring the second set of multiple lines as sense electrodes in the self-capacitance configuration;

uncoupling the first set of multiple lines from the sense amplifier;

coupling the first set of multiple lines to a shield buffer and coupling the input of the shield buffer to the shield voltage; and

coupling the sense amplifier with the second set of multiple lines.

11. The device of claim 10, wherein configuring the first set of multiple lines as drive lines comprises coupling one or more stimulation sources to the first set of multiple lines.

12. The device of claim 10, wherein configuring the first set and second set of multiple lines as sense electrodes comprises coupling a set of sensing circuits to the first and second sets of multiple lines.

13. The device of claim 12, wherein the sensing circuitry used to configure the first set of multiple lines as sense electrodes is the same sensing circuitry used to configure the second set of multiple lines as sense electrodes.

14. The device of claim 12, wherein the sensing circuitry is connected to a DC voltage source during the mutual capacitance mode and to an AC voltage source the self-capacitance mode.

15. The device of claim 10, wherein the processor is further capable of:

configuring the first set of multiples lines to be connected to a voltage source while sensing the second set of multiple lines; and

configuring the second set of multiple lines to be connected to the voltage source while sensing the first set of multiple lines.

16. The device of claim 15, wherein the voltage source produces a signal having substantially the same frequency and phase as a stimulation signal used to sense the first set of multiple lines and the second set of multiple lines.

17. The device of claim 16, wherein the voltage source is also used to stimulate the first set of multiple lines while sensing the first set of multiple lines and to stimulate the second set of multiple lines while sensing the second set of multiple lines.

18. The device of claim 10, wherein the sense amplifier comprises an input switchably coupled to a first line of the first set of multiple lines and to a second line of the second set of multiple lines.

19. A non-transitory computer readable storage medium having stored thereon a set of instructions for switching a touch sensor panel between a self-capacitance mode and a mutual capacitance mode, that when executed by a processor causes the processor to:

in the mutual capacitance mode;

configure a first set of multiple lines as drive lines in a mutual capacitance configuration; and

uncoupling the first set of multiple lines and the second set of multiple lines from a shield buffer and coupling an input of the shield buffer to a reference voltage; and

configure a second set of multiple lines as sense lines in the mutual capacitance configuration; and

in the self-capacitance mode;

configure the first set of multiple lines as sense electrodes in a self-capacitance configuration;

uncouple the second set of multiple lines from a sense amplifier;

coupling the second set of multiple lines to a shield buffer and coupling the input of the shield buffer to a shield voltage, different from the reference voltage;

couple the first set of multiple lines with the sense amplifier;

configure the second set of multiple lines as sense electrodes in the self-capacitance configuration;

uncouple the first set of multiple lines from the sense amplifier;

coupling the first set of multiple lines to a shield buffer and coupling the input of the shield buffer to the shield voltage; and

couple the second set of multiple lines with the sense amplifier.

20. The non-transitory computer readable storage medium of claim 19, wherein configuring the first set of multiple lines as drive lines comprises coupling one or more stimulation sources to the first set of multiple lines.

21. The non-transitory computer readable storage medium of claim 19, wherein configuring the first set and second set of multiple lines as sense electrodes comprises coupling a set of sensing circuits to the first and second set of multiple lines.

22. The non-transitory computer readable storage medium of claim 21, wherein the sensing circuitry used to configure the first set of multiple lines as sense electrodes is the same sensing circuitry used to configure the second set of multiple lines as sense electrodes.

23. The non-transitory computer readable storage medium of claim 21, wherein the sensing circuitry is connected to a DC voltage source during the mutual capacitance mode and to an AC voltage source during the self-capacitance mode.

24. The non-transitory computer readable storage medium of claim 19, wherein the processor is further caused to:

configure the first set of multiples lines to be connected to a voltage source while sensing the second set of multiple lines; and

configure the second set of multiple lines to be connected to the voltage source while sensing the first set of multiple lines.

25. The non-transitory computer readable storage medium of claim 24, wherein the voltage source produces a signal having substantially the same frequency and phase as a stimulation signal used to sense the first set of multiple lines and the second set of multiple lines.

26. The non-transitory computer readable storage medium of claim 25, wherein the voltage source is also used to stimulate the first set of multiple lines while sensing the first set of multiple lines and to stimulate the second set of multiple lines while sensing the second set of multiple lines.

27. The non-transitory computer readable storage medium of claim 19, wherein the processor is further capable of switchably coupling an input of the sense amplifier to a first line of the first set of multiple lines and to a second line of the second set of multiple lines.