High speed low power multi-touch touch device and controller therefor

• US 8,493,358 B2
• Filed: 05/19/2011
• Issued: 07/23/2013
• Est. Priority Date: 05/25/2010
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Rebeschi, Thomas J., Cordeiro, Craig A.
• Primary Examiner(s): Haley, Joseph
• Assistant Examiner(s): HOFFNER, LINH NGUYEN
• Application Number:
  US13/111,084
• Publication Number:
  US 20110291986A1
• Time in Patent Office: 796 Days
• Field of Search: 345/173, 345/174, 345/178, 345/179, 178/18.06, 178/18.07, 178/18.08, 178/19.01, 178/19.03, 178/19.04, 324/610, 324/611
• US Class Current: 345/174
• CPC Class Codes: G06F 2203/04104 Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

A touch-sensitive device includes a touch panel, a drive unit, a sense unit, and a measurement unit. A touch applied to a node of the panel changes a capacitive coupling between two electrodes (a drive electrode and a sense electrode) of the touch panel. The drive unit delivers a drive signal, which may comprise one or more drive pulses, to the drive electrode. The sense unit couples to the sense electrode, and generates a response signal that that is used to accumulate charge in a charge accumulator to provide an accumulated signal. The accumulated signal is responsive to the capacitive coupling between the electrodes, and is measured to provide an indication of a touch at the node.

Claims

1. A touch-sensitive apparatus, comprising:

a panel comprising a touch surface and a plurality of electrodes defining an electrode matrix, the plurality of electrodes comprising a plurality of drive electrodes and a plurality of receive electrodes, each drive electrode being capacitively coupled to each receive electrode at a respective node of the matrix, the panel being configured such that a touch on the touch surface proximate a given one of the nodes changes a coupling capacitance between the drive electrode and the receive electrode associated with the given node;

a drive unit configured to generate drive signals and to deliver the drive signals to the drive electrodes;

a sense unit including an open-loop transistor-based amplifier and configured to generate, in response to the drive signals, response signals for the plurality of receive electrodes, an amplitude of each of the response signals being responsive to the coupling capacitance at the associated node;

a charge accumulator adapted to provide an accumulated signal for each node based on a corresponding response signal generated by the sense unit; and

a measurement unit configured to measure the accumulated signals from the charge accumulator and to determine therefrom the positions of multiple temporally overlapping touches, if present, on the touch surface.

2. The apparatus of claim 1, wherein the transistor-based amplifier is unipolar.

3. The apparatus of claim 1, wherein the transistor-based amplifier comprises a first and second transistor.

4. The apparatus of claim 3, wherein the transistor-based amplifier includes no transistors other than the first and second transistors.

5. The apparatus of claim 3, wherein a collector of the first transistor couples to a base of the second transistor.

6. The apparatus of claim 3, wherein the charge accumulator is coupled between an emitter of the first transistor and a collector of the second transistor.

7. The apparatus of claim 1, wherein the sense unit further comprises a reference circuit coupled between the drive unit and the transistor-based amplifier.

8. The apparatus of claim 7, wherein the reference circuit generates the response signals, and the response signals are differentiated representations of the drive signals, the differentiation of each response signal being based on the coupling capacitance of the node associated with the response signal.

9. The apparatus of claim 7, wherein the reference circuit includes a resistance through which the coupling capacitance is discharged.

10. The apparatus of claim 7, wherein the transistor-based amplifier comprises a first and second transistor, and wherein a base of the first transistor couples to the reference circuit, and a collector of the first transistor couples to a base of the second transistor.

11. The apparatus of claim 7, wherein the transistor-based amplifier comprises a first and second transistor, and wherein the reference circuit is adapted to bias a base of the first transistor.

12. The apparatus of claim 7, wherein the reference circuit is unipolar.

13. The apparatus of claim 12, wherein the transistor-based amplifier is also unipolar.

14. The apparatus of claim 1, further comprising a reset circuit configured to reset the charge accumulator.

15. The apparatus of claim 1, wherein the measurement unit converts each accumulated signal into a digital representation.