Common mode noise mitigation for integrated touch screens
Some touch screens can be formed by at least partially integrating touch sensing circuitry into a display pixel stackup. In some examples, noise can be introduced into touch sensor panel measurements, for example, from display data lines of a display device proximate to the touch sensor panel. In some examples, rows or columns of touch electrodes can be split and a first portion of the touch sensor panel can be stimulated to measure capacitance and noise and a second portion of the touch sensor panel can be unstimulated and measure noise. In some examples, both the first and the second portions of the touch sensor panel can be stimulated using orthogonal stimulation codes. In some examples, measurements from the first and/or second portions of the touch sensor panel can be subtracted from measurements from the other portion of the touch sensor panel to eliminate or reduce common mode noise.
1. A device comprising:
drive circuitry configured to stimulate drive electrodes of a touch sensor panel;
sense circuitry configured to receive sense signals from sense electrodes of the touch sensor panel; and
logic circuitry coupled to the drive circuitry and the sense circuitry, configured to:
during a first phase of a mutual capacitance scan of the touch sensor panel:
simultaneously driving a first plurality of drive electrodes;
sensing one or more first sense signals from one or more first sense electrodes, wherein the one or more first sense signals includes a first touch signal and a first common mode noise signal;
sensing one or more second sense signals from one or more second sense electrodes, wherein the one or more second sense signals includes a second common mode noise signal; and
filtering the first common mode noise from the one or more first sense signals based on the second common mode noise signal from the one or more second sense signals; and
during a second phase of the mutual capacitance scan of the touch sensor panel:
simultaneously driving a second plurality of drive electrodes, different from the first plurality of drive electrodes;
sensing one or more third sense signals from the one or more second sense electrodes, wherein the one or more third sense signals includes a second touch signal and a third common mode noise signal;
sensing one or more fourth sense signals from the one or more first sense electrodes, wherein the one or more fourth sense signals includes a fourth common mode noise signal;
filtering a third common mode noise from the one or more third sense signals based on the fourth common mode noise signal from the one or more fourth sense signals.
2. The device of claim 1 , wherein at least one of the one or more first sense electrodes and at least one of the one or more second sense electrodes are arranged in a column.
3. The device of claim 1 , wherein:
the one or more first sense signals and the one or more second sense signals are concurrently sensed; and
the one or more third sense signals and the one or more fourth sense signals are concurrently sensed.
4. The device of claim 1 , further comprising:
a first display drive electrode, disposed beneath the one or more first sense electrodes and the one or more second sense electrodes, configured to provide data to a display.
5. The device of claim 1 , wherein the sense circuitry comprises:
a first single-ended amplifier coupled to one of the one or more first sense electrodes;
a second single-ended amplifier coupled to one of the one or more second sense electrodes; and
a summing circuit configured to subtract an output of the second single-ended amplifier from an output of the first single-ended amplifier.
6. The device of claim 1 , wherein the sense circuitry comprises:
a first single-ended amplifier coupled to one of the one or more first sense electrodes;
a second single-ended amplifier coupled to one of the one or more second sense electrodes;
a common mode amplifier, coupled to the one of the one or more first sense electrodes and one of the one or more second sense electrodes, configured to filter common mode noise; and
an analog-to-digital converter (ADC).
7. The device of claim 1 , wherein the sense circuitry comprises:
a first differential amplifier coupled to one of the one or more first sense electrodes and one of the one or more second sense electrodes;
a common mode amplifier, coupled to the one of the one or more first sense electrodes and one of the one or more second sense electrodes, configured to filter common mode noise; and
an analog-to-digital converter (ADC).
8. The device of claim 1 , wherein the sense circuitry comprises:
a first differential amplifier coupled to one of the one or more first sense electrodes and one of the one or more second sense electrodes; and
an analog-to-digital converter (ADC).
9. The device of claim 1 , wherein:
the sense circuitry comprises a plurality of sense channels, including a first sense channel and a second sense channel, wherein the sense circuitry is configured to:
during a first sense mode:
perform a differential measurement using the first sense channel and the second sense channel; and
during a second sense mode:
perform a first single-ended measurement using the first sense channel; and
perform a second single-ended measurement using the second sense channel.
10. A method comprising:
during a first phase of a mutual capacitance scan of a touch sensor panel:
simultaneously driving a first plurality of drive electrodes;
sensing one or more first sense signals from one or more first sense electrodes, wherein the one or more first sense signals includes a first touch signal and a first common mode noise signal;
sensing one or more second sense signals from one or more second sense electrodes, wherein the one or more second sense signals includes a second common mode noise signal; and
filtering the first common mode noise from the one or more first sense signals based on the second common mode noise signal from the one or more second sense signals; and
during a second phase of the mutual capacitance scan of the touch sensor panel:
simultaneously driving a second plurality of drive electrodes, different from the first plurality of drive electrodes;
sensing one or more third sense signals from the one or more second sense electrodes, wherein the one or more third sense signals includes a second touch signal and a third common mode noise signal;
sensing one or more fourth sense signals from the one or more first sense electrodes, wherein the one or more fourth sense signals includes a fourth common mode noise signal; and
filtering a third common mode noise from the one or more third sense signals based on the fourth common mode noise signal from the one or more fourth sense signals.
11. The method of claim 10 , wherein the one or more first sense signals and the one or more second sense signals are concurrently sensed.
12. The method of claim 10 , further comprising:
during a first sense mode:
performing a differential measurement using a first sense channel and a second sense channel; and
during a second sense mode:
performing a first single-ended measurement using the first sense channel; and
performing a second single-ended measurement using the second sense channel.
13. A non-transitory computer readable storage medium, the computer readable medium containing instructions that, when executed by a device including one or more processors, performs a method comprising:
during a first phase of a mutual capacitance scan of the touch sensor panel:
simultaneously driving a first plurality of drive electrodes;
sensing one or more first sense signals from one or more first sense electrodes, wherein the one or more first sense signals includes a first touch signal and a first common mode noise signal;
sensing one or more second sense signals from one or more second sense electrodes, wherein the one or more second sense signals includes a second common mode noise signal; and
filtering the first common mode noise from the one or more first sense signals based on the second common mode noise signal from the one or more second sense signals; and
during a second phase of the mutual capacitance scan of the touch sensor panel:
simultaneously driving a second plurality of drive electrodes, different from the first plurality of drive electrodes;
sensing one or more third sense signals from the one or more second sense electrodes, wherein the one or more third sense signals includes a second touch signal and a third common mode noise signal;
sensing one or more fourth sense signals from the one or more first sense electrodes, wherein the one or more fourth sense signals includes a fourth common mode noise signal; and
filtering a third common mode noise from the one or more third sense signals based on the fourth common mode noise signal from the one or more fourth sense signals.
14. The non-transitory computer readable storage medium of claim 13 , wherein the one or more first sense signals and the one or more second sense signals are concurrently sensed.
15. The non-transitory computer readable storage medium of claim 13 , the method further comprising:
during a first sense mode:
performing a differential measurement using a first sense channel and a second sense channel; and
during a second sense mode:
performing a first single-ended measurement using the first sense channel; and
performing a second single-ended measurement using the second sense channel.