Sensing unit, sensing arrangement and sensing method for touch panel application

• US 8,952,922 B2
• Filed: 04/27/2011
• Issued: 02/10/2015
• Est. Priority Date: 04/30/2010
• Status: Active Grant

• Current Assignee: Elan Microelectronics Corporation
• Original Assignee: Elan Microelectronics Corporation
• Inventors: Lin, Chia-Hsing, Tao, Yi-Hsin, Hsu, Wen-Jun, Lee, I-Shu, Hsu, Shih-Yuan
• Primary Examiner(s): Wang-Hurst, Kathy
• Assistant Examiner(s): Tung, David
• Application Number:
  US13/095,134
• Publication Number:
  US 20110267312A1
• Time in Patent Office: 1,385 Days
• Field of Search: 345173-174, 324/600, 324658-690
• US Class Current: 345/174
• CPC Class Codes: G06F 2203/04107 Shielding in digitiser, i.e. guard or shielding arrangements, mostly for capacitive touchscreens, e.g. driven shields, driven grounds
• 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

Two sensing units are configured as an exciter and a sensor connected to two trace lines, respectively, for mutual capacitance sensing from the capacitance units including these two trace lines. The two sensing units connect the two trace lines together to balance them to a same voltage level first, and then disconnect them from each other. Thereafter, the exciter connects the first trace line to an excitation node to induce a charge change on the second trace line, and the sensor senses the charge change to detect the variation of the mutual capacitance between the two trace lines.

Claims

1. A sensing arrangement for touch panel application, comprising:

a first sensing unit connected to a first trace line, when the first sensing unit operates with an exciter mode, the first sensing unit has a first phase and a second phase, and switches the first trace line to connect to an excitation node during the second phase; and

a second sensing unit connected to a second trace line and connected to the first sensing unit through an equalization line, when the second sensing unit operates with a sensor mode, the second sensing unit has the first phase and the second phase, and supplies a charge current to the second trace line and generates a mirror current proportional to the charge current during the second phase;

wherein the first and the second sensing units use the equalization line to balance the first and second trace lines to a same voltage level during the first phase;

wherein the first sensing unit comprises;

a first equalization switch connected between the first trace line and the equalization line;

an excitation switch connected between the first trace line and the excitation node; and

a first current mirror connected to the first trace line through a charge switch;

wherein the second sensing unit comprises;

a second equalization switch connected between the second trace line and the equalization line;

a second current mirror operative to supply the charge current and generate the mirror current; and

a sample switch connected between the second current mirror and the output node.

2. The sensing arrangement of claim 1, wherein the excitation node is grounded.

3. The sensing arrangement of claim 1, further comprising an integrator connected to the output node for accumulating charges of the mirror current so as to generate an output voltage.

4. The sensing arrangement of claim 3, wherein the integrator comprises a capacitor.

5. The sensing arrangement of claim 3, further comprising a reset switch connected to the output node for resetting the integrator.

6. The sensing arrangement of claim 1, wherein the second sensing unit further comprises:

a second charge switch connected between the second trace line and the second current mirror; and

a ground switch connected between the second trace line and a ground node.

7. The sensing arrangement of claim 6, wherein the second sensing unit further comprises a second excitation switch connected between the second trace line and a the excitation node.

8. The sensing arrangement of claim 1, wherein the first and second sensing units are located in two different sensing chips, respectively.

9. The sensing arrangement of claim 1, wherein the multiple operational modes further comprises a fixed-driven mode for fixing the second trace line to the excitation node.

10. The sensing arrangement of claim 1, wherein the multiple operational modes further comprises a non-driven mode for making the second trace line floating.