Mutual-capacitance sensing with conductive overlay

Patent metadata

Field	Value
Publication number	US-12050751-B2
Application number	US-202117564499-A
Country	US
Kind code	B2
Filing date	Dec 29, 2021
Priority date	Sep 20, 2019
Publication date	Jul 30, 2024
Grant date	Jul 30, 2024

Abstract

A device includes an electrical circuit and a mutual-capacitance sensing circuit coupled to the electrical circuit. The mutual-capacitance sensing circuit includes mutual-capacitance sensing electrodes including a transmitter electrode and receiver electrode. The device also includes a conductive overlay over the mutual-capacitance sensing electrodes. The mutual-capacitance sensing circuit is configured to detect deflection of a portion of the conductive overlay relative to the mutual-capacitance sensing electrodes. The receiver electrode has a shape with an inner edge, and the transmitter electrode has a shape with an outer edge that is at least partially surrounded by the inner edge of the receiver electrode.

First claim

What is claimed is:

1. A device, comprising:
a first electrode including a first electrode outer edge, a first surface disposed on a substrate, and a second surface opposite the first surface; and
a second electrode including a second electrode inner edge, a second electrode outer edge, a third surface disposed on the substrate and a fourth surface opposite the third surface;
a space material disposed on the substrate; and
a conductive layer over the second surface of the first electrode, the conductive layer having a first portion disposed on the spacer material and a second portion that is configured to deflect toward the first and second electrodes, wherein the first electrode is disposed on the surface in an area aligned with a maximum deflection of the second portion and the second electrode is disposed on the substrate in an area not aligned with the maximum deflection.

2. The device of claim 1 , wherein the second portion of the conductive layer is configured to deflect such that a distance between an inner surface of the second portion and the second surface of the first electrode is less than a distance between the inner surface of the second portion and the fourth surface of the second electrode.

3. The device of claim 2 , wherein:
the second portion of the conductive layer comprises a concave upper surface and a convex lower surface when the second portion is deflected.

4. The device of claim 2 , wherein:
the conductive layer is electrically isolated from the first electrode and the second electrode.

5. The device of claim 1 , wherein:
the conductive layer is coupled to a ground potential.

6. The device of claim 1 , wherein:
the first electrode is a planar first electrode; and
the second electrode is a planar second electrode.

7. The device of claim 1 , wherein:
the second electrode inner edge is disposed adjacent to the first electrode outer edge.

8. The device of claim 1 , wherein:
the first electrode outer edge is at least partially surrounded by the second electrode inner edge.

9. The device of claim 1 , wherein the second electrode comprises a first surface and a second surface opposite the first surface, wherein the first surface is disposed on the substrate and the conductive layer is disposed over the second surface of the second electrode.

10. The device of claim 1 , wherein the second surface of the first electrode comprises a circular surface.

11. The device of claim 1 , wherein:
a position of the first electrode relative to the second electrode is based on one of an application, a monitoring portion size, and a desired sensitivity.

12. The device of claim 1 , wherein:
an inner edge of the spacer material at least partially surrounds the second electrode outer edge.

13. The device of claim 12 , wherein:
a thickness of the spacer material represents an offset distance between an inner surface of the second portion of the conductive layer and the second surface of the first electrode.

14. The device of claim 13 , wherein:
deflection of the second portion of the conductive layer results in a reduced offset distance.

15. A device, comprising:
a first electrode including a first electrode outer edge, a first surface disposed on a substrate, and a second surface opposite the first surface; and
a second electrode including a second electrode inner edge and a second electrode outer edge;
a conductive layer over the second surface of the first electrode; and
a spacer material between the conductive layer and the first electrode, wherein a thickness of the spacer material represents an offset distance, wherein deflection of the conductive layer results in a reduced offset distance, and wherein the reduced offset distance results in a distorted sense signal at the second electrode.

16. The device of claim 15 , wherein:
the distorted sense signal charges a capacitor.

17. The device of claim 16 , further comprising:
a signal analyzer configured to assert a deflection detection signal in response to a charge of the capacitor being less than a threshold.

18. The device of claim 16 , further comprising:
a signal analyzer configured to assert a deflection detection signal in response to a charge of the capacitor being between an upper threshold and a lower threshold.

19. The device of claim 15 , wherein:
the distorted sense signal includes a positive peak and a negative peak.

20. The device of claim 19 , wherein:
the positive peak is detected based on one of a plurality of distortion parameters including:
a rising slope of the positive peak;
a falling slope of the positive peak; and
a change in a peak magnitude of the positive peak.

Assignees

• Texas Instruments Inc

Inventors

• Spevak Peter

Classifications

• G06F3/0448

  Details of the electrode shape, e.g. for enhancing the detection of touches, for generating specific electric field shapes, for enhancing display quality · CPC title

• G06F3/0416

  Control or interface arrangements specially adapted for digitisers · CPC title

• G06F2203/04107

  Shielding in digitiser, i.e. guard or shielding arrangements, mostly for capacitive touchscreens, e.g. driven shields, driven grounds · CPC title

• G06F3/0445

  using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer · CPC title

• G06F3/0444 Primary

  using a single conductive element covering the whole sensing surface, e.g. by sensing the electrical current flowing at the corners · CPC title