Electronic device including device ground coupled finger coupling electrode and array shielding electrode and related methods

• US 9,581,628 B2
• Filed: 05/03/2013
• Issued: 02/28/2017
• Est. Priority Date: 05/04/2012
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Setlak, Dale R., Gozzini, Giovanni
• Primary Examiner(s): Pappas, Claire X
• Assistant Examiner(s): CASAREZ, BENJAMIN X.
• Application Number:
  US13/886,520
• Publication Number:
  US 20130314105A1
• Time in Patent Office: 1,397 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• CPC Class Codes: G01R 3/00 Apparatus or processes specially adapted for the manufacture or maintenance of measuring instruments , e.g. of probe tips
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing
• CPC Class Codes: G06V 40/1329 Protecting the fingerprint sensor against damage caused by the finger
• CPC Class Codes: Y10T 29/49204 Contact or terminal manufacturing

Abstract

An electronic device may include a housing and circuitry carried by the housing and having a device ground associated therewith. The electronic device may also include an array of biometric finger sensing pixel electrodes and an array shielding electrode outside the array of biometric finger sensing pixels. A finger coupling electrode may be outside the array shielding electrode and coupled to the device ground. The electronic device may also include drive circuitry capable of generating a drive signal for the array of biometric finger sensing pixel electrodes and a compensating drive signal for the array shielding electrode.

Claims

1. An electronic device comprising:

a housing;

circuitry carried by said housing and having a device ground associated therewith;

an array of biometric finger sensing pixel electrodes configured to sense biometric data;

an array shielding electrode outside said array of biometric finger sensing pixels;

a finger coupling electrode outside said array shielding electrode and coupled to the device ground, the finger coupling electrode being coupled to the device ground causing noise in the sensed biometric data relative to the finger coupling electrode; and

drive circuitry capable of generating a drive signal for said array of biometric finger sensing pixel electrodes and a compensating drive signal comprising a scaled replica of the drive signal for said array shielding electrode, the compensating drive signal reducing the noise in the sensed biometric data.

2. The electronic device of claim 1, further comprising sense amplifier circuitry coupled to said array of biometric finger sensing pixel electrodes and having a circuit reference associated therewith different than the device ground;

and wherein said drive circuitry is capable of generating the drive signal between the device ground and the circuit reference.

3. The electronic device of claim 1, wherein said array shielding electrode comprises a plurality of shielding pixel electrodes.

4. The electronic device of claim 1, further comprising a reference electrode between said array shielding electrode and said array of biometric finger sensing pixel electrodes.

5. The electronic device of claim 4, further comprising a dummy biometric finger sensing pixel electrode area between said array of biometric finger sensing pixel electrodes and said reference electrode.

6. The electronic device of claim 1, further comprising a dielectric cap over said array of biometric finger sensing pixel electrodes.

7. The electronic device of claim 1, further comprising a semiconductor substrate carrying said array of biometric finger sensing pixel electrodes.

8. The electronic device of claim 1, wherein said circuitry comprises wireless communications circuitry capable of performing at least one wireless communications function.

9. The electronic device of claim 1, further comprising an input device carrying said array of biometric finger sensing pixel electrodes.

10. The electronic device of claim 1, wherein said drive circuitry is capable of generating the drive signal as a square wave at an amplitude in a range of 10 to 20 volts and at a frequency of 1 to 5 MHz.

11. A finger biometric sensor to be coupled to circuitry carried by a housing of an electronic device, the circuitry having a device ground associated therewith, the finger biometric sensor comprising:

an array of biometric finger sensing pixel electrodes configured to sense biometric data;

an array shielding electrode outside said array of biometric finger sensing pixels;

a finger coupling electrode outside said array shielding electrode and coupled to the device ground, the finger coupling electrode being coupled to the device ground causing noise in the sensed biometric data relative to the finger coupling electrode; and

drive circuitry capable of generating a drive signal for said array of biometric finger sensing pixel electrodes and a compensating drive signal comprising a scaled replica of the drive signal for said array shielding electrode, the compensating drive signal reducing noise in the sensed biometric data.

12. The finger biometric sensor of claim 11, further comprising sense amplifier circuitry coupled to said array of biometric finger sensing pixel electrodes and having a circuit reference associated therewith different than the device ground;

and wherein said drive circuitry is capable of generating the drive signal between the device ground and the circuit reference.

13. The finger biometric sensor of claim 11, wherein said array shielding electrode comprises a plurality of shielding pixel electrodes.

14. The finger biometric sensor of claim 11, further comprising a reference electrode between said array shielding electrode and said array of biometric finger sensing pixel electrodes.

15. The finger biometric sensor of claim 14, further comprising a dummy biometric finger sensing pixel electrode area between said array of biometric finger sensing pixel electrodes and said reference electrode.

16. The finger biometric sensor of claim 11, further comprising a dielectric cap over said array of biometric finger sensing pixel electrodes.

17. The finger biometric sensor of claim 11, further comprising a semiconductor substrate carrying said array of biometric finger sensing pixel electrodes.

18. The finger biometric sensor of claim 11, wherein said drive circuitry is capable of generating the drive signal as a square wave at an amplitude in a range of 10 to 20 volts and at a frequency of 1 to 5 MHz.

19. A method of making an electronic device comprising circuitry having a device ground associated therewith, the method comprising:

forming an array shielding electrode outside an array of biometric finger sensing pixel electrodes;

forming a finger coupling electrode outside the array shielding electrode and coupled to the device ground, the finger coupling electrode being coupled to the device ground causing noise in sensed biometric data relative to the finger coupling electrode; and

forming drive circuitry capable of generating a drive signal for the array of biometric finger sensing pixels and a compensating drive signal comprising a scaled replica of the drive signal for the array shielding electrode, the compensating drive signal reducing the noise in the sensed biometric data.

20. The method of claim 19, further comprising forming sense amplifier circuitry coupled to the array of biometric finger sensing pixel electrodes and having a circuit reference associated therewith different than the device ground;

and wherein the drive circuitry is capable of generating the drive signal between the device ground and the circuit reference.

21. The method of claim 19, wherein forming the array shielding electrode comprises forming a plurality of shielding pixel electrodes.

22. The method of claim 19, further comprising forming a reference electrode between the array shielding electrode and the array of biometric finger sensing pixel electrodes.

23. The method of claim 22, further comprising forming a dummy biometric finger sensing pixel electrode area between the array of biometric finger sensing pixel electrodes and the reference electrode.

24. The method of claim 19, further comprising positioning a dielectric cap over the array of biometric finger sensing pixel electrodes.

25. The method of claim 19, wherein forming the drive circuitry comprises forming the drive circuitry to be capable of generating the drive signal as a square wave at an amplitude in a range of 10 to 20 volts and at a frequency of 1 to 5 MHz.