Display noise filter for a sensing device
An input device comprises a plurality of sensor electrodes and a processing system coupled to the plurality of sensor electrodes. The processing system comprises a sensor driver. The sensor driver comprises clock synchronization circuitry, a blocking pulse generator, and a sensor module. The clock synchronization circuitry is configured to receive an external clock signal, and synchronize an internal clock signal with the external clock signal. The blocking pulse generator is configured to generate a first blocking pulse based on the internal clock signal. The sensor module comprises sensing circuitry and is configured to pause acquisition of a resulting signal from a sensor electrode based on the first blocking pulse.
1. A sensor driver comprising:
clock synchronization circuitry configured to:
receive an external clock signal from a source external to the sensor driver, wherein the external clock signal is generated by a display driver; and
synchronize an internal clock signal of the sensor driver with the external clock signal;
a blocking pulse generator configured to generate a first blocking pulse having at least one of a rising edge and a falling edge associated with the synchronized internal clock signal; and
a sensor module comprising sensing circuitry and configured to pause acquisition of a resulting signal from a sensor electrode based on the first blocking pulse, wherein the sensor module further comprises:
a mixer; and
an analog-to-digital converter coupled to the mixer, wherein pausing the acquisition of the resulting signal comprises disconnecting the mixer from the analog-to-digital converter based on the rising edge of the first blocking pulse.
2. The sensor driver of claim 1 , wherein a width of the first blocking pulse is wider than a width of a first pulse of the synchronized internal clock signal.
3. The sensor driver of claim 2 , wherein the rising edge of the first blocking pulse occurs before or is aligned with a rising edge of the first pulse of the synchronized internal clock signal, and wherein the falling edge of the first blocking pulse occurs after a falling edge of the first pulse of the synchronized internal clock signal.
4. The sensor driver of claim 1 , wherein a width of the first blocking pulse is larger than a width of a pulse of the external clock signal.
5. The sensor driver of claim 1 , wherein the blocking pulse generator is further configured to generate a second blocking pulse, and wherein a width of the second blocking pulse is greater than or equal to a width of the first blocking pulse.
6. The sensor driver of claim 1 ,
wherein pausing the acquisition of the resulting signal comprises one of:
multiplying a mixing signal with the first blocking pulse; and
phase delaying the mixing signal with the first blocking pulse.
7. The sensor driver of claim 1 , wherein synchronizing the internal clock signal of the sensor driver with the external clock signal comprises adjusting a master clock signal of the sensor driver based on the external clock signal.
8. A method for capacitive sensing, the method comprising:
synchronizing an internal clock signal of a sensor driver with an external clock signal generated by a display driver external to the sensor driver;
generating a blocking pulse having at least one of a rising edge and a falling edge associated with the synchronized internal clock signal; and
pausing acquisition of a resulting signal from a sensor electrode with receiver circuitry based on the blocking pulse, wherein pausing the acquisition of the resulting signal comprises disconnecting a mixer of the sensor driver from an analog-to-digital converter coupled to the mixer based on the rising edge of the blocking pulse.
9. The method of claim 8 , wherein a width of the blocking pulse is wider than a width of a pulse of the synchronized internal clock signal.
10. The method of claim 8 , wherein the rising edge of the blocking pulse is aligned with or occurs before a rising edge of a pulse of the synchronized internal clock signal.
11. The method of claim 10 , wherein the falling edge of the blocking pulse is aligned with or occurs after a falling edge of the pulse of the synchronized internal clock signal.
12. The method of claim 8 , wherein a width of the blocking pulse is larger than a width of a pulse of the external clock signal.
13. The method of claim 8 , wherein pausing the acquisition of the resulting signal comprises one of:
multiplying a mixing signal of the mixer with the blocking pulse; and
phase delaying the mixing signal with the blocking pulse.
14. An input device comprising:
a plurality of sensor electrodes; and
a processing system coupled to the plurality of sensor electrodes, the processing system comprising:
a sensor driver having an internal clock signal and configured to:
receive an external clock signal from a display driver external to the sensor driver;
synchronize the internal clock signal with the external clock signal;
generate a blocking pulse having at least one of a rising edge and a falling edge associated with the synchronized internal clock signal; and
pause acquisition of a resulting signal from the sensor electrode of the plurality of sensor electrodes based on the blocking pulse, wherein the input device further comprises:
a mixer; and
an analog-to-digital converter coupled to the mixer, and wherein pausing the acquisition of the resulting signal comprises disconnecting the mixer from the analog-to-digital converter based on the rising edge of the blocking pulse.
15. The input device of claim 14 , wherein a width of the blocking pulse is wider than a width of a pulse of the synchronized internal clock signal.
16. The input device of claim 14 , wherein the rising edge of the blocking pulse is aligned with or occurs before a rising edge of a pulse of the synchronized internal clock signal.
17. The input device of claim 16 , wherein the falling edge of the blocking pulse is aligned with or occurs after a falling edge of the pulse of the synchronized internal clock signal.
18. The input device of claim 14 , wherein pausing the acquisition of the resulting signal comprises one of:
multiplying a mixing signal of the mixer with the blocking pulse; and
phase delaying the mixing signal with the blocking pulse.
19. The input device of claim 14 further comprising a display panel and wherein the display driver is configured to update the display panel, wherein the external clock signal is a horizontal synchronization signal of the display driver.
20. The sensor driver of claim 1 wherein the external clock signal generated by the display driver is a horizontal synchronization signal.
21. The method of claim 8 , wherein the external clock signal generated by the display driver is a horizontal synchronization signal.