Detection of defects in touch sensors

Patent metadata

Field	Value
Publication number	US-9921683-B2
Application number	US-201213483465-A
Country	US
Kind code	B2
Filing date	May 30, 2012
Priority date	May 30, 2012
Publication date	Mar 20, 2018
Grant date	Mar 20, 2018

Abstract

Defects in a touch sensor are detected by coupling the sensor lines to a common signal line. Each of the sensor lines is tested by disconnecting the sensor line from the common signal line, connecting it to a voltage (e.g., ground) and comparing the voltage on the common signal line to a reference voltage. Detected defects include a short circuit between any two transmit and/or receive lines and a short between any transmit or receive line to ground.

First claim

What is claimed is:

1. A method of detecting defects associated with sensor lines in a touch sensor comprising:
controlling one of a first plurality of switches to couple a first sensor line of a plurality of sensor lines to a first voltage;
controlling a second plurality of switches to simultaneously couple other sensor lines of the plurality of sensor lines to a common signal line; and
while the other sensor lines are simultaneously coupled to the common signal
line and the first sensor line is coupled to the first voltage and is disconnected from the common signal line, comparing a voltage present on the common signal line to a reference voltage to determine if a defect exists that is associated with the first sensor line.

2. A method of detecting defects associated with sensor lines in a touch sensor comprising:
simultaneously coupling a plurality of sensor lines to a common signal line; and
while the plurality of sensor lines are simultaneously coupled to the common signal line:
coupling a first voltage to a first sensor line that is disconnected from the common signal line; and
comparing a voltage present on the common signal line to a reference voltage to determine if a defect exists that is associated with the first sensor line;
decoupling the first sensor line from the first voltage;
coupling the first sensor line to the common signal line;
disconnecting a second sensor line from the common signal line, a second plurality of sensor lines being simultaneously coupled to the common signal line; and
while the second plurality of sensor lines are simultaneously coupled to the common signal line: coupling the disconnected second sensor line to the first voltage; and
comparing the voltage present on the common signal line to the reference voltage to determine if a defect exists that is associated with the disconnected second sensor line.

3. The method as recited in claim 2 wherein the plurality of sensor lines includes transmit lines and receive lines of a touch sensor.

4. The method as recited in claim 1 further comprising supplying as the reference voltage a bandgap voltage reference.

5. The method as recited in claim 1 further comprising supplying a second voltage to the common signal line.

6. The method as recited in claim 5 further comprising supplying as the reference voltage a voltage value that is less than the second voltage.

7. The method as recited in claim 6 wherein the reference voltage is approximately half the second voltage.

8. The method as recited in claim 1 wherein the first voltage is ground.

9. The method as recited in claim 8 further comprising determining the defect exists in response to the voltage present on the common signal line being lower than the reference voltage.

10. The method as recited in claim 1 wherein the plurality of sensor lines includes transmit lines and receive lines of the touch sensor.

11. An apparatus comprising:
a plurality of sensor lines in a touch panel;
a first plurality of switches to selectively couple the plurality of sensor lines to a common signal line;
a second plurality of switches to selectively couple the plurality of sensor lines to a first voltage;
control logic configured to couple a first sensor line of the plurality of sensor lines to the first voltage through one of the second plurality of switches and configured to simultaneously couple other sensor lines of the plurality of sensor lines to the common signal line through corresponding switches of the first plurality of switches; and
compare logic to compare a voltage on the common signal line to a reference voltage while the first sensor line is coupled to the first voltage and the other sensor lines are simultaneously coupled to the common signal line,
wherein a value of an output of the compare logic indicates whether a defect exists in the first sensor line.

12. The apparatus as recited in claim 11 wherein the control logic is further configured to cause an output of the compare logic to be stored.

13. The apparatus as recited in claim 11 wherein the control logic is further configured to:
decouple the first sensor line from the first voltage;
couple the first sensor line to the common signal line;
decouple a second sensor line of the plurality of sensor lines from the common signal line while others of the plurality of sensor lines remain coupled to the common signal line; and
couple the second sensor line to the first voltage.

14. The apparatus as recited in claim 11 wherein the reference voltage is a bandgap voltage reference.

15. The apparatus as recited in claim 11 wherein the voltage on the common signal line is at a second voltage, absent a defect, and at a third voltage if there is a defect in the first sensor line.

16. The apparatus as recited in claim 15 wherein a value of the second voltage, absent a defect, is higher than the third voltage.

17. The apparatus as recited in claim 11 further comprising a voltage divider circuit supplying the reference voltage.

18. The apparatus as recited in claim 11 wherein the first voltage is ground.

19. The apparatus as recited in claim 11 wherein the other sensor lines of the plurality of sensor lines includes transmit lines and receive lines of a touch sensor.

Assignees

• Cooley Daniel J
• Sonntag Jeffrey L
• Silicon Lab Inc

Inventors

• Cooley Daniel J
• Sonntag Jeffrey L

Classifications

• G06F3/0418 Primary

  for error correction or compensation, e.g. based on parallax, calibration or alignment · CPC title

• G01R31/025

  Physics · mapped topic

• G01R31/52

  Testing for short-circuits, leakage current or ground faults · CPC title

• G06F3/0446

  using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes · CPC title