Method and apparatus for improved input sensing using a display processor reference signal
Embodiments of the invention generally provide a method and apparatus that is configured to reduce the effects of interference that is undesirably provided to a transmitter signal that is delivered from a transmitter signal generating device to a sensor processor to determine if an input object is disposed within a touch sensing region of a touch sensing device. In one embodiment, the sensor processor includes a receiver channel that has circuitry that is configured to separately receive a transmitter signal delivered from a display processor and a sensor processor reference signal that is based on a display processor reference signal to reliably sense the presence of an object. Embodiments of the invention described herein thus provide an improved apparatus and method for reliably sensing the presence of an object by a touch sensing device.
1. An input device, comprising:
a plurality of transmitter electrodes, wherein each of the plurality of transmitter signals comprises at least one common electrode of the display configured to be driven for display updating and capacitive sensing;
a plurality of receiver electrodes;
a display processor configured to drive at least one transmitter electrode of the plurality transmitter electrodes with a transmitter signal for capacitive sensing; and
a sensor processor configured to receive resulting signals with the plurality of receiver electrodes when the at least one transmitter electrode is driven, wherein the sensor processor comprises:
one or more receiver channels, and wherein each of the one or more receiver channels is configured to be coupled to at least one sensor electrode of the plurality of receiver electrodes; and
a reference channel configured to provide a reference channel output signal, wherein the reference channel has a first reference channel input port that is configured to receive a reference channel input signal, wherein the reference channel input signal is based on the transmitter signal; and wherein each of the one or more receiver channels is configured to provide an output signal based on at least a portion of the resulting signals and the reference channel output signal.
2. The input device of claim 1 , wherein the sensor processor further comprises a second reference channel configured to provide a second reference channel output signal, wherein the second reference channel is configured to receive a second reference channel input signal, wherein the second reference channel input signal is based on the transmitter signal.
3. The input device of claim 2 , wherein the output signal is further based on the second reference channel output signal.
4. The input device of claim 1 , wherein the one or more receiver channels is coupled to a sensor processor reference signal that is based on at least one of a display processor reference signal.
5. The input device of claim 4 , wherein the display processor reference signal is configured to be electrically coupled to a ground of the sensor processor.
6. The input device of claim 1 , wherein the reference channel comprises a second reference channel input port that is configured to receive a sensor processor reference signal based on a display processor reference signal.
7. The input device of claim 1 , wherein reference channel comprises a charge accumulator, wherein the first reference channel input port is coupled to a first input of the charge accumulator.
8. The input device of claim 1 further comprising a capacitive element coupled to the first reference channel input port and wherein said transmitter signal is driven onto the capacitive element.
9. A sensor processor for an input device, comprising:
a sensor circuitry coupled to a plurality of sensor electrodes, wherein the sensor processor is coupled to a display processor that is configured to drive a plurality of common electrodes for updating a display device, wherein the sensor processor comprises at least one receiver channel configured to receive resulting signals with at least one of the plurality of sensor electrodes, wherein said resulting signals comprise effects corresponding to a transmitter signal, and a reference channel configured to provide a reference channel output signal, wherein the reference channel has a first reference channel input port that is configured to receive a reference channel input signal, wherein the reference channel input signal is based on the transmitter signal; and wherein each of the one or more receiver channels is configured to provide an output signal based on at least a portion of the resulting signals and the reference channel output signal.
10. The sensor processor of claim 9 , wherein a display processor reference signal is configured to be electrically coupled to a ground of the sensor processor.
11. The sensor processor of claim 9 , wherein the transmitter signal is configured to be capacitively coupled to the first reference channel input port.
12. The sensor processor of claim 9 , wherein the sensor processor further comprises a second reference channel configured to provide a second reference channel output signal, wherein the second reference channel is configured to receive a second reference channel input signal, wherein the second reference channel input signal is based on the transmitter signal.
13. The sensor processor of claim 12 , wherein the output signal is further based on the second reference channel output signal.
14. The sensor processor of claim 9 , wherein the at least receiver channels is coupled to a sensor processor reference signal that is based on at least one of a display processor reference signal.
15. The sensor processor of claim 9 , wherein the display processor is further configured to drive the plurality of common electrodes for capacitive sensing with the transmitter signal.
16. A processing system for an input device, the processing system comprising:
a display processor configured to drive a plurality of common electrodes for updating a display device, the display processor configured to drive at least one common electrode of the plurality of common electrodes with a transmitter signal for capacitive sensing; and
a sensor processor configured to receive resulting signals with the plurality of receiver electrodes when the at least one common electrode of the plurality of common electrodes is driven with the transmitter signal, wherein the sensor processor comprises one or more receiver channels, and wherein each of the one or more receiver channels is configured to be coupled to at least one sensor electrode of the plurality of receiver electrodes; and a reference channel configured to provide a reference channel output signal, wherein the reference channel has a first reference channel input port that is configured to receive a reference channel input signal, wherein the reference channel input signal is based on the transmitter signal; and wherein each of the one or more receiver channels is configured to provide an output signal based on at least a portion of the resulting signals and the reference channel output signal.
17. The processing system of claim 16 , wherein the transmitter signal is configured to be capacitively coupled to the first reference channel input port.
18. The processing system of claim 16 , wherein the sensor processor further comprises a second reference channel configured to provide a second reference channel output signal, wherein the second reference channel is configured to receive a second reference channel input signal, wherein the second reference channel input signal is based on the transmitter signal.
19. The processing system of claim 18 , wherein the output signal is further based on the second reference channel output signal.
20. The processing system of claim 16 , wherein the at least receiver channels is coupled to a sensor processor reference signal that is based on at least one of a display processor reference signal.