Charge pump having AC and DC outputs for touch panel bootstrapping and substrate biasing

• US 9,806,608 B2
• Filed: 02/12/2016
• Issued: 10/31/2017
• Est. Priority Date: 02/13/2015
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Yao, Weijun, Stronks, David A., Bae, Hopil, Brahma, Kingsuk, Yao, Wei Hsin, Bi, Yafei, Li, Yingxuan
• Primary Examiner(s): Cheng, Joe H
• Application Number:
  US15/043,405
• Publication Number:
  US 20160241139A1
• Time in Patent Office: 627 Days
• CPC Class Codes: G06F 1/3262 Power saving in digitizer or tablet
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• 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 3/044 by capacitive means
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• CPC Class Codes: H01L 23/642 Capacitive arrangements H01L23/49589, H01L23/645, H01L23/647, H01L23/66 take precedence; capacitive effects between wiring layers on the semiconductor body H01L23/5222
• CPC Class Codes: H02M 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps

Abstract

A charge pump that can be configured to operate in a first mode and a second mode is disclosed. The charge pump can comprise a charging capacitor coupled to a first node and configured to transfer a first DC voltage to the first node. The charge pump can also comprise a first output node and a second output node coupled to the first node. During the first mode, the first output node can be configured to output a second DC voltage based on the first DC voltage, and the second output node can be configured to output a third DC voltage based on the first DC voltage. During the second mode, the first output node can be configured to output the second DC voltage, and the second output node can be configured to output an AC voltage, the AC voltage being offset by the third DC voltage.

Claims

1. A charge pump configured to operate in a first mode and a second mode, the charge pump comprising:

a charging capacitor coupled to a first node and configured to transfer a first direct current (DC) voltage to the first node;

a first output node coupled to the first node; and

a second output node coupled to the first node,

wherein;

during the first mode, the first output node is configured to output a second DC voltage based on the first DC voltage, and the second output node is configured to output a third DC voltage based on the first DC voltage, and

during the second mode, the first output node is configured to output the second DC voltage based on the first DC voltage, and the second output node is configured to output an alternating current (AC) voltage, the AC voltage being offset by the third DC voltage.

2. The charge pump of claim 1, wherein:

the first output node is coupled to the first node via a first switch, and

the second output node is coupled to the first node via a second switch.

3. The charge pump of claim 2, wherein the first switch and the second switch are controlled by a single clock signal.

4. The charge pump of claim 2, wherein the first switch and the second switch are controlled by different clock signals.

5. The charge pump of claim 1, wherein the second DC voltage and the third DC voltage are the same.

6. The charge pump of claim 1, further comprising:

a first holding capacitor having a first terminal and a second terminal, the first terminal coupled to the first output node; and

a second holding capacitor having a third terminal and a fourth terminal, the third terminal coupled to the second output node,

wherein the second DC voltage is further based on the first holding capacitor, and the third DC voltage is further based on the second holding capacitor.

7. The charge pump of claim 6, wherein the first holding capacitor and the second holding capacitor have substantially the same capacitance.

8. The charge pump of claim 6, wherein:

the second terminal of the first holding capacitor is coupled to a first reference DC voltage, and

the fourth terminal of the second holding capacitor is coupled to;

a second reference DC voltage during the first mode, and

an AC voltage source during the second mode.

9. The charge pump of claim 8, wherein the first reference DC voltage and the second reference DC voltage are ground voltages.

10. The charge pump of claim 8, further comprising:

switching circuitry coupled between;

the fourth terminal of the second holding capacitor, and

the second reference DC voltage and the AC voltage source,

wherein during the first mode, the switching circuitry is configured to couple the fourth terminal of the second holding capacitor to the second reference DC voltage, and during the second mode, the switching circuitry is configured to couple the fourth terminal of the second holding capacitor to the AC voltage source.

11. The charge pump of claim 1, wherein the first output node is configured to be coupled to a substrate on which the charge pump is formed.

12. The charge pump of claim 1, wherein the second output node is configured to be coupled to the touch screen.

13. The charge pump of claim 12, wherein the second output node is configured to be coupled to a gate line of a display pixel included in the touch screen.

14. The charge pump of claim 13, wherein the second output node is further configured to be coupled to sense circuitry, the sense circuitry configured to sense touch at the display pixel.

15. A charge pump configured to operate in a first mode and a second mode, the charge pump comprising:

means for transferring a first direct current (DC) voltage to a first node;

means for coupling a first output node to the first node; and

means for coupling a second output node to the first node,

wherein;

during the first mode, the first output node is configured to output a second DC voltage based on the first DC voltage, and the second output node is configured to output a third DC voltage based on the first DC voltage, and

during the second mode, the first output node is configured to output the second DC voltage based on the first DC voltage, and the second output node is configured to output an alternating current (AC) voltage, the AC voltage being offset by the third DC voltage.

16. The charge pump of claim 15, further comprising:

means for coupling a first terminal of a first holding capacitor to the first output node, the first holding capacitor having the first terminal and a second terminal;

means for coupling a third terminal of a second holding capacitor to the second output node, the second holding capacitor having the third terminal and a fourth terminal,

wherein the second DC voltage is further based on the first holding capacitor, and the third DC voltage is further based on the second holding capacitor.

17. The charge pump of claim 16, wherein:

the second terminal of the first holding capacitor is coupled to a first reference DC voltage, and

the fourth terminal of the second holding capacitor is coupled to;

a second reference DC voltage during the first mode, and

an AC voltage source during the second mode.

18. The charge pump of claim 17, further comprising:

means for;

during the first mode, coupling the fourth terminal of the second holding capacitor to the second reference DC voltage, and

during the second mode, coupling the fourth terminal of the second holding capacitor to the AC voltage source.

19. The charge pump of claim 15, further comprising:

means for coupling the first output node to a substrate on which the charge pump is formed.

20. The charge pump of claim 15, further comprising:

means for coupling the second output node to a gate line of a display pixel included in a touch screen.

21. A method of operating a charge pump in a first mode and a second mode, the method comprising:

transferring a first direct current (DC) voltage to a first node;

coupling a first output node to the first node; and

coupling a second output node to the first node,

wherein;

during the first mode, the first output node is configured to output a second DC voltage based on the first DC voltage, and the second output node is configured to output a third DC voltage based on the first DC voltage, and

during the second mode, the first output node is configured to output the second DC voltage based on the first DC voltage, and the second output node is configured to output an alternating current (AC) voltage, the AC voltage being offset by the third DC voltage.

22. The method of claim 21, further comprising:

coupling a first terminal of a first holding capacitor to the first output node, the first holding capacitor having the first terminal and a second terminal;

coupling a third terminal of a second holding capacitor to the second output node, the second holding capacitor having the third terminal and a fourth terminal,

wherein the second DC voltage is further based on the first holding capacitor, and the third DC voltage is further based on the second holding capacitor.

23. The method of claim 22, further comprising:

coupling the second terminal of the first holding capacitor to a first reference DC voltage;

during the first mode, coupling the fourth terminal of the second holding capacitor to a second reference DC voltage; and

during the second mode, coupling the fourth terminal of the second holding capacitor to an AC voltage source.

24. The method of claim 21, further comprising:

coupling the first output node to a substrate on which the charge pump is formed.

25. The method of claim 21, further comprising:

coupling the second output node to a gate line of a display pixel included in a touch screen.