COMMON MODE NOISE REDUCTION IN CAPACITIVE TOUCH SENSING

• US 20170185182A1
• Filed: 12/29/2015
• Published: 06/29/2017
• Est. Priority Date: 12/29/2015
• Status: Active Grant

• Current Assignee: STMicroelectronics International N.V. (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Asia Pacific Pte Limited (STMicroelectronics NV)
• Inventors: CHANDRAN, Praveesh, KORAPATI, Lokesh Kumar, NAGARAJAN, Mythreyi
• Granted Patent: US 10,120,509 B2
• Time in Patent Office: Days
• CPC Class Codes: G06F 2203/04102 Flexible digitiser, i.e. constructional details for allowing the whole digitising part of a device to be flexed or rolled like a sheet of paper
• 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 3/0443 using a single layer of sensing electrodes

Abstract

The present disclosure is directed to a system and method to remove common mode noise projected onto a touch sensor array from a display. The system is configured to activate two rows of electrodes at the same time, while coupling remaining rows of electrodes to ground. A first one of the two activated rows is used for detection of a touch and a second one of the two activated rows is used to detect common mode noise from the display. The common mode noise detected by the second row is removed from signals received from a plurality of columns of the touch sensor array.

Claims

1. A device, comprising:

a touch sensor array that includes;

a plurality of rows, each row having a plurality of electrodes;

a plurality of columns of electrodes, each column having a plurality of electrodes;

a plurality of first current to voltage amplifiers, each one of the plurality of first current to voltage amplifiers coupled to one the plurality of columns;

a plurality of differential amplifiers, each one of the plurality of differential amplifiers coupled to one of the plurality of first current to voltage amplifiers; and

a second current to voltage amplifier configured to be coupled to one of the plurality of rows, an output of the second current to voltage amplifier being coupled to each one of the plurality of differential amplifiers.

2. The device of claim 1, further comprising a transparent layer on the touch sensor array.

3. The device of claim 2, further comprising a display, the touch sensor array being positioned between the transparent layer and the display.

4. The device of claim 3 wherein the display includes a polarizing layer and a thin film transistor layer.

5. The device of claim 3 wherein the display is flexible.

6. The device of claim 3 wherein a distance between the display and the touch sensor array is less than 10 microns.

7. A method, comprising:

reducing parasitic capacitance in a touch sensor from a display, the reducing including;

activating a plurality of columns of electrodes;

activating a first row of electrodes of a plurality of rows of electrodes;

coupling a second row of electrodes to a noise-reducing circuit; and

coupling remaining ones of the plurality of rows of electrodes to ground.

8. The method of claim 7, further comprising detecting a touch by a user with the plurality of column electrodes.

9. The method of claim 8, further comprising determining a third row of electrodes to activate based on a location of the touch.

10. A system, comprising:

a display;

a touch sensor array coupled to the display, the touch sensor array including;

a plurality of rows of electrodes;

a plurality of columns of electrodes; and

a plurality of amplifiers, a first one of the plurality of amplifiers coupled to one of the plurality of rows of electrodes and each remaining amplifier coupled to one of the plurality of columns of electrodes.

11. The system of claim 10 wherein the touch sensor array includes a plurality of differential amplifiers, each differential amplifier coupled to the first one of the plurality of amplifiers.

12. The system of claim 11 wherein each differential amplifier is coupled to one of the remaining amplifiers that are coupled to the ones of the plurality of columns of electrodes.

13. The system of claim 10, further comprising a touch sensor controller configured to activate and deactivate the plurality of rows and columns of electrodes of the touch sensor array.

14. The system of claim 10, further comprising an application specific integrated circuit coupled to the remaining amplifiers that are coupled to one of the plurality of columns of electrodes.

15. The system of claim 10 wherein the display is a liquid crystal display.