METHOD AND APPARATUS FOR REDUCING COUPLED NOISE INFLUENCE IN TOUCH SCREEN CONTROLLERS

• US 20150205438A1
• Filed: 02/02/2015
• Published: 07/23/2015
• Est. Priority Date: 10/20/2009
• Status: Active Grant

• Current Assignee: Parade Technologies, Ltd.
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Kremin, Viktor, Konovalov, Anton
• Granted Patent: US 9,229,577 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/04184 Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally
• 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

Apparatuses and methods to reduce the influence of a noise signal on touch screen controllers are described. One apparatus includes a detector to determine a presence of a noise signal from a display coupled to a capacitive touch screen. The apparatus also includes a synchronization circuit to synchronize signals produced by a touch screen controller with the noise signal to reduce the influence of the noise signal on capacitance measurements by the touch screen controller.

Claims

1-20. -20. (canceled)

21. An apparatus comprising:

a detector to determine a presence of a noise signal from a display coupled to a capacitive touch screen; and

a synchronization circuit to synchronize signals produced by a touch screen controller with the noise signal to reduce an influence of the noise signal on capacitance measurements by the touch screen controller.

22. The apparatus of claim 21, wherein the synchronization circuit is a state machine.

23. The apparatus of claim 21, wherein the detector to determine the presence of the noise signal is to sense the noise signal on one or more electrodes of the capacitive touch screen that are not being scanned to detect a touch proximate the capacitive touch screen.

24. The apparatus of claim 23, wherein the one or more electrodes of the capacitive touch screen are scanned to detect the touch proximate the capacitive touch screen while the one or more electrodes are not being used by the detector to determine the presence of the noise signal.

25. The apparatus of claim 23, wherein the one or more electrodes of the capacitive touch screen are solely used by the detector to determine the presence of the noise signal.

26. The apparatus of claim 21, wherein the synchronization circuit to synchronize the signals produced by the touch screen controller with the noise signal is to

synchronize transmission (Tx) signals with the noise signal.

27. The apparatus of claim 21, further comprising

a counter to produce output pulses coupled to the synchronization circuit to produce a measurement in response to the output pulses, the counter to stop responsive to an output indicative of the presence of the noise signal, the synchronization circuit configured to be disabled when the counter is stopped.

28. The apparatus of claim 21, further comprising

a multiplexor to selectively connect one or more electrodes of the capacitive touch screen to the detector.

29. The apparatus of claim 21, further comprising

a noise filter to average the noise signal over a measurement interval.

30. The apparatus of claim 21, wherein the detector comprises a threshold comparator coupled to selected outputs of the display to produce an output indicative of the presence of the noise signal.

31. The apparatus of claim 30, wherein the detector is a digital circuit.

32. The apparatus of claim 30, wherein the selected outputs of the display comprise at least one transmission (Tx) electrode and at least one receiving (Rx) electrode.

33. The apparatus of claim 21, further comprising

a timer responsive to the detector to measure a duration between a selected number of noise pulses in at least one of a first mode and a second mode when the noise signal is pulsed noise.

34. The apparatus of claim 21, further comprising

a timeout counter to produce output pulses if the presence of the noise signal is not detected, the timeout counter coupled to the synchronization circuit to produce a measurement in response to the output pulses

35. A method comprising:

performing a listening scan to determine a presence of a noise signal from a display coupled to a capacitive touch screen;

generating signals to detect a touch proximate the capacitive touch screen; and

synchronizing the signals with the noise signal to reduce an influence of the noise signal on capacitance measurements used to detect the touch.

36. The method of claim 35, wherein performing a listening scan to determine the presence of the noise signal further comprises

scanning during a first window of time one or more electrodes of the capacitive touch screen to determine the presence of the noise signal.

37. The method of claim 36, wherein the generating the signals to detect the touch proximate the capacitive touch screen further comprises

scanning during a second window of time the one or more electrodes of the capacitive touch screen to detect the touch, wherein the first window of time is different than the second window of time.

38. The method of claim 35, further comprising

filtering the noise signal by using at least one of a window filter, an averaging filter, or a median filter.

39. A system comprising:

a display to produce images and a noise signal;

a capacitive touch screen overlaying the display;

a touch screen controller, coupled to the capacitive touch screen, comprising a detector and a synchronization circuit,

the detector to determine a presence of the noise signal from the display; and

the synchronization circuit to synchronize signals produced by the touch screen controller with the noise signal to reduce an influence of the noise signal on capacitance measurements by the touch screen controller.

40. The system of claim 39, wherein the detector to determine the presence of the noise signal is to sense the noise signal on one or more electrodes of the capacitive touch screen that are not being scanned to detect a touch proximate the capacitive touch screen.