Capacitive Sensing Array Having Electrical Isolation

• US 20150070079A1
• Filed: 09/09/2013
• Published: 03/12/2015
• Est. Priority Date: 09/09/2013
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Yang, Zhiping, Wang, Hanfeng
• Granted Patent: US 10,296,773 B2
• Time in Patent Office: Days
• US Class Current: 327/517
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing

Abstract

A capacitive fingerprint sensor that may be formed of an array of sensing elements. Each capacitive sensing element of the array may register a voltage that varies with the capacitance of a capacitive coupling. A finger may capacitively couple to the individual capacitive sensing elements of the sensor, such that the sensor may sense a capacitance between each capacitive sensing element and the flesh of the fingerprint. The capacitance signal may be detected by sensing the change in voltage on the capacitive sensing element as the relative voltage between the finger and the sensing chip is changed. Alternately, the capacitance signal may be detected by sensing the change in charge received by the capacitive sensing elements as the relative voltage between the finger and the sensing chip is changed.

Claims

1. An electronic device, comprising:

a sensor chip comprising an array of individual capacitive sensing elements;

an electronic component positioned nearby the sensor pad within the electronic device; and

an electrical isolation wall electrically separating the sensor pad and electronic component.

2. The electronic device of claim 1, wherein the electrical isolation wall comprises at least one electrical component electrically connected to the sensor chip.

3. The electronic device of claim 2, wherein the electrical isolation wall is electrically connected to a controller chip, the controller chip operative to supply a voltage to the sensor chip.

4. The electronic device of claim 3, wherein:

the controller chip is operative to supply a first voltage to the sensor chip along a first voltage path; and

the sensor chip is further operative to supply a second voltage to the sensor chip along a second voltage path.

5. The electronic device of claim 4, wherein

a first inductor is connected between the controller chip and the sensor chip as part of the first voltage path;

and

a second inductor is connected between the controller chip and the sensor chip as part of the second voltage path.

6. The electronic device of claim 5, wherein a ground of the controller chip and a ground of the sensor chip are electrically connected by a ground path;

and

a third inductor forms at least a portion of the ground path.

7. The electronic device of claim 6, further comprising:

a clock signal path from the controller chip to the sensor chip; and

a resistor in-line in the clock signal path.

8. The electronic device of claim 7, wherein the electrical isolation wall comprises the first inductor, the second inductor, the third inductor and the resistor.

9. The electronic device of claim 8, wherein the electronic component is an antenna.

10. An electronic device, comprising:

a housing;

an antenna at least partially within the housing;

an input element separate from and adjacent the housing;

a sensor positioned beneath the input element;

a controller chip electrically connected to the sensor; and

an electrical isolation element electrically isolating the antenna from the sensor.

11. The electronic device of claim 10, wherein the sensor is a biometric sensor.

12. The electronic device of claim 10, wherein the antenna comprises a cellular antenna.

13. The electronic device of claim 12, wherein the electrical isolation element filters high-frequency signals from traveling between the sensor and the antenna.

14. The electronic device of claim 13, wherein the electrical isolation element comprises at least one inductor operative to filter AC signal components.

15. The electronic device of claim 14, wherein the filter cutoff is 100 MHz.

16. The electronic device of claim 10, further comprising a drive ring electrically coupled to the sensor.

17. The electronic device of claim 10, wherein the electrical isolation element comprises a plurality of electronic components, at least one electronic component in-line with each of a plurality of electrical connections between a controller chip and the sensor.

18. The electronic device of claim 17, wherein the plurality of electrical connections comprise:

at least one voltage path;

at least one clock signal path; and

at least one ground path.

19. The electronic device of claim 18, further comprising a diode in-line in the at least one voltage path and serially connected to one of the plurality of electronic components.

20. The electronic device of claim 19, further comprising a capacitor operative to supply voltage through the diode to the sensor at least momentarily during operation of the sensor.

21. The electronic device of claim 20, wherein the capacitor and diode are positioned adjacent one another.

22. The electronic device of claim 21, further comprising a second capacitor positioned between the diode and a ground of the controller chip;

wherein

the second capacitor is positioned adjacent the diode 706 in a silicon layout.

23. The electronic device of claim 22, wherein the capacitor, diode and second capacitor are physically positioned to minimize an inductance of a current loop through the diode.