System and method for determining resistance in an input device

• US 8,952,925 B2
• Filed: 03/22/2012
• Issued: 02/10/2015
• Est. Priority Date: 03/22/2012
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Bulea, Mihai
• Primary Examiner(s): Boddie, William
• Assistant Examiner(s): Gyawali, Bipin
• Application Number:
  US13/427,202
• Publication Number:
  US 20130249850A1
• Time in Patent Office: 1,055 Days
• Field of Search: None
• US Class Current: 345/174
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• 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

Abstract

A processing system for an input device includes a transmitter module, a receiver module, and a determination module. The transmitter module includes transmitter circuitry and is configured to apply a first differential drive signal across a transmitter electrode to produce a first voltage variation across the transmitter electrode. The receiver module is configured to receive a first resulting signal with a receiver electrode when the first voltage variation is produced across the transmitter electrode. The determination module is configured to determine at least one of a resistance of the transmitter electrode and a resistance of a conductive trace coupled to the transmitter electrode based on the first resulting signal. As a result, an error in the position of an input object can be corrected.

Claims

1. A processing system for an input device, the processing system comprising:

a transmitter module including transmitter circuitry, the transmitter module configured to apply a first differential drive signal across a transmitter electrode to produce a first voltage variation across the transmitter electrode;

a receiver module, the receiver module configured to receive a first resulting signal with a receiver electrode when the first voltage variation is produced across the transmitter electrode; and

a determination module configured to determine at least one of a resistance of the transmitter electrode and a resistance of a conductive trace coupled to the transmitter electrode based on the first resulting signal;

wherein applying the first differential drive signal comprises;

substantially simultaneously driving a first end of the transmitter electrode with a first drive signal and driving a second end of the transmitter electrode with a second drive signal.

2. The processing system of claim 1, wherein the transmitter module is further configured to apply a second differential drive signal across the transmitter electrode to produce a second voltage variation across the transmitter electrode, wherein

the receiver module is further configured to receive a second resulting signal when the second voltage variation is produced across the transmitter electrode, and wherein

the determination module is further configured to determine at least one of the resistance of the transmitter electrode and the resistance of the conductive trace coupled to the transmitter electrode based on the second resulting signal.

3. The processing system of claim 2, wherein the transmitter module is further configured to apply a third differential drive signal across the transmitter electrode to produce a third voltage variation across the transmitter electrode, wherein

the receiver module is configured to receive a third resulting signal when the third voltage variation is produced across the transmitter electrode, and wherein

the determination module is further configured to determine at least one of the resistance of the transmitter electrode and the resistance of the conductive trace coupled to the transmitter electrode based on the third resulting signal.

4. The processing system of claim 2, wherein the first differential drive signal has a first amplitude, the second differential drive signal has a second amplitude, and wherein the first amplitude is different from the second amplitude.

5. The processing system of claim 1, wherein applying the first differential drive signal comprises substantially simultaneously driving a first end of the transmitter electrode with a first drive signal having a first polarity and driving a second end of the transmitter electrode with a second drive signal having a second polarity, and wherein the first polarity is different from the second polarity.

6. The processing system of claim 1, wherein the first drive signal is mathematically independent of the second drive signal.

7. A capacitive sensor device comprising:

a transmitter electrode;

a conductive trace coupled to the transmitter electrode;

a receiver electrode; and

a processing system communicatively coupled to the transmitter electrode and the receiver electrode, the processing system configured to;

apply a first differential drive signal across the transmitter electrode to produce a first voltage variation across the transmitter electrode;

receive with the receiver electrode a first resulting signal when the first voltage variation is produced across the transmitter electrode; and

determine at least one of a resistance of the transmitter electrode and a resistance of the conductive trace based on the first resulting signal;

wherein applying the first differential drive signal comprises substantially simultaneously driving a first end of the transmitter electrode with a first drive signal and driving a second end of the transmitter electrode with a second drive signal.

8. The capacitive sensor device of claim 7, wherein the processing system is further configured to apply a second differential drive signal across the transmitter electrode to produce a second voltage variation,

receive with the receiver electrode a second resulting signal when the second voltage variation is produced across the transmitter electrode, and

determine at least one of a resistance of the transmitter electrode and a resistance of the conductive trace coupled to the transmitter electrode based on the second resulting signal.

9. The capacitive sensor device of claim 8, the processing system further configured to:

apply a third differential drive signal across the transmitter electrode to produce a third voltage variation across the transmitter electrode,

receive a third resulting signal when the third voltage variation is produced across the transmitter electrode, and

determine at least one of the resistance of the transmitter electrode and the resistance of the conductive trace coupled to the transmitter electrode based on the third resulting signal.

10. The capacitive sensor device of claim 8, wherein the first differential drive signal has a first amplitude, the second differential drive signal has a second amplitude, and wherein the first amplitude is different from the second amplitude.

11. The capacitive sensor device of claim 7, wherein the first drive signal has a first polarity and the second drive signal has a second polarity, and wherein the first polarity is different from the second polarity.

12. The capacitive sensor device of claim 7, wherein applying the first differential drive signal comprises substantially simultaneously driving a first end of the transmitter electrode with a first drive signal and driving a second end of the transmitter electrode with a substantially constant voltage.

13. The capacitive sensor device of claim 7, wherein applying the first differential drive signal comprises:

substantially simultaneously driving a first end of the transmitter electrode with a first drive signal and driving a second end of the transmitter electrode with a second drive signal, wherein the first drive signal is substantially orthogonal to the second drive signal.

14. A method of determining resistances in an input device having a transmitter electrode and a conductive trace coupled thereto, the method comprising:

applying a first differential drive signals across the transmitter electrode to produce a first voltage variation across the transmitter electrode;

receiving with a receive electrode a first resulting signal comprising effects of the first voltage variation when the first voltage variation is produced across the transmitter electrode; and

determining at least one of a resistance of the transmitter electrode and a resistance of the conductive trace based on the first resulting signal;

wherein applying the first differential drive signal comprises substantially simultaneously driving a first end of the transmitter electrode with a first drive signal and driving a second end of the transmitter electrode with a second drive signal.

15. The method of claim 14, further comprising:

applying a second differential drive signal across the transmitter electrode to produce a second voltage variation across the transmitter electrode;

receiving a second resulting signal when the second voltage variation is produced across the transmitter electrode; and

determining at least one of the resistance of the transmitter electrode and the resistance of the conductive trace coupled to the transmitter electrode based on the second resulting signal.

16. The method of claim 15, further comprising:

applying a third differential drive signal across the transmitter electrode to produce a third voltage variation across the transmitter electrode;

receiving a third resulting signal when the third voltage variation is produced across the transmitter electrode; and

determining at least one of the resistance of the transmitter electrode and the resistance of the conductive trace coupled to the transmitter electrode based on the third resulting signal.

17. The method of claim 15, wherein the first differential drive signal has a first amplitude, the second differential drive signal has a second amplitude, and wherein the first amplitude is different from the second amplitude.

18. The method of claim 14, wherein the first drive signal has a first polarity and the second drive signal has a second polarity, and wherein the first polarity is different from the second polarity.

19. The method of claim 14, wherein applying the first differential drive signal comprises substantially simultaneously driving a first end of the transmitter electrode with a first drive signal and driving a second end of the transmitter electrode with a substantially constant voltage.

20. The method of claim 14, wherein applying the first differential drive signal comprises:

substantially simultaneously driving a first end of the transmitter electrode with a first drive signal and driving a second end of the transmitter electrode with a second drive signal, wherein the first drive signal is substantially orthogonal to the second drive signal.