System for and method of protecting an integrated circuit from over currents

• US 20070207681A1
• Filed: 04/03/2006
• Published: 09/06/2007
• Est. Priority Date: 04/08/2005
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Atrua Technologies Incorporated (Apple Inc.)
• Inventors: Ngo, Hung, Zabroda, Oleksiy, Cheng, Ericson
• Granted Patent: US 8,231,056 B2
• Time in Patent Office: Days
• US Class Current: 439/717
• CPC Class Codes: G06V 40/1329 Protecting the fingerprint sensor against damage caused by the finger

Abstract

A contact detector having power switches for disconnecting power to portions of the contact sensor when an over current is detected is disclosed. The power switches thus protect the contact sensor from over-current as the result of latch-up or other current-generating conditions. These current-generating conditions are often the result of ESD events on a surface of the contact detector. A contact detector comprises an exposed surface for detecting the presence of an object, an insulating surface, and a protection element disposed under the insulating surface for controlling power to the contact detector. The protection element is configured to disconnect power to the contact detector when a current to the contact detector is detected above a threshold. Preferably, the contact detector is a finger swipe sensor, but it can be a finger placement sensor or any other type of device that functions on contact with a finger or other patterned object.

Claims

1. A contact detector comprising:

a. an exposed surface for detecting the presence of an object;

b. an insulating surface; and

c. a protection element disposed under the insulating surface for controlling power to the contact detector.

2. The contact detector of claim 1, wherein the protection element is configured to disconnect power to the contact detector when a current to the contact detector is detected above a threshold.

3. The contact detector of claim 2, wherein the contact detector forms a finger image sensor.

4. The contact detector of claim 3, wherein the finger image sensor is a finger swipe sensor.

5. The contact detector of claim 4, wherein the finger swipe sensor is a capacitive sensor comprising a sensing array.

6. The contact detector of claim 3, wherein the finger image sensor is a finger placement sensor.

7. The contact detector of claim 1, wherein the exposed surface overlies an analog block for capturing analog data generated by contacting the contact detector and a digital block for processing digital data generated from the analog data.

8. The contact detector of claim 7, wherein the analog data is finger image data and the digital data corresponds to the finger image data.

9. The contact detector of claim 8, wherein the first protection element comprises a first switch for controlling power to the analog block and a second switch first for controlling power to the digital block.

10. The contact detector of claim 9, wherein the first switch and the second switch are configured to cooperatively disconnect power to the analog block and the digital block and selectively reconnect power to the analog block and the digital block.

11. The contact detector of claim 1, further comprising a state machine for placing each of the first switch and the second switch into a selected one of an operating mode, a stand-by mode, and a disconnect mode.

12. The contact detector of claim 1, wherein the insulating surface borders opposing ends of the exposed surface.

13. The contact detector of claim 1, wherein the insulating surface surrounds the exposed surface.

14. A fingerprint sensor comprising:

a. an exposed surface overlying a plurality of blocks, each block containing a contact detector element for detecting the presence of a patterned image on the exposed surface;

b. an insulating surface; and

c. a plurality of protection elements disposed under the insulating surface for controlling power to the plurality of blocks.

15. The fingerprint sensor of claim 14, wherein each protection element from the plurality of protection elements is configured to disconnect power to a corresponding block from the plurality of blocks when a current to the block exceeds a threshold.

16. The fingerprint sensor of claim 15, wherein the plurality of blocks comprise an array of sensing elements for capturing fingerprint images.

17. The fingerprint sensor of claim 15, wherein the plurality of blocks also comprise digital components for processing swiped finger image data.

18. The fingerprint sensor of claim 14, wherein the insulating surface comprises a non-conductive material.

19. The fingerprint sensor of claim 18, wherein the insulating material further comprises a grounded conductive material overlying the non-conductive material.

20. The fingerprint sensor of claim 15, wherein signals transmitted to and from the plurality of power elements are static.

21. A method of forming a fingerprint sensor comprising:

a. forming electronic components in a semiconductor substrate for capturing finger image data;

b. forming a power protection element in the semiconductor substrate for controlling power to the electronic components; and

c. forming an insulating layer over the power protection element, thereby leaving a surface over the electronic components exposed and the power protection element un-exposed.

22. The method of claim 21, wherein the electronic components form a finger swipe sensor.

23. The method of claim 21, wherein the electronic components form a finger placement sensor.

24. The method of claim 21, further comprising coupling a state machine to the power protection element, wherein the state machine is for controlling the power protection element to selectively disconnect power to the electronic components in the event an over current is detected on the electronic components.

25. The method of claim 24, wherein the state machine is also for controlling the power protection element to selectively reconnect power to the first electronic components after a pre-determined time.

26. The method of claim 21, wherein the state machine is disposed under the insulating layer.

27. The method of claim 21, wherein the insulating layer comprises a non-conductive material.

28. The method of claim 21, wherein the power protection element generates and receives static control signals.

29. The method of claim 21, wherein the electronic components comprise transistors and forming electronic components and forming a power protection element both comprise spacing the transistors to minimize latch-up.

30. A method of forming a fingerprint sensor comprising:

a. forming multiple electronics components in a semiconductor substrate, the multiple electronics for capturing and processing finger image data;

b. forming multiple power protection elements in the semiconductor substrate, each power protection element for controlling power to a corresponding one of the multiple electronic components; and

c. forming a protection layer over the multiple power protection elements, thereby leaving the multiple electronic components exposed and the multiple power protection elements un-exposed.

31. The method of claim 30, wherein the multiple electronics form a finger swipe sensor.

32. The method of claim 30, wherein the multiple electronics for a finger placement sensor.