Capacitive sensor driving technique that enables hybrid sensing or equalization

• US 9,459,367 B2
• Filed: 02/10/2014
• Issued: 10/04/2016
• Est. Priority Date: 10/02/2013
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Ludden, Christopher A.
• Primary Examiner(s): Koval, Melissa
• Assistant Examiner(s): Monsur, Nasima
• Application Number:
  US14/176,952
• Publication Number:
  US 20150226871A1
• Time in Patent Office: 967 Days
• Field of Search: 324/676, 324/658, 324/649, 324/600, 324/661, 324/679, 324/686, 345/174, 345/173, 345/179, 345/104, 345/158, 345/175
• US Class Current: 1/1
• CPC Class Codes: G01V 3/08 operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices with electromagnetic waves G01V3/12

Abstract

Embodiments described herein include an input device that drives an equalization signal onto an electrode that may be capacitively coupled to a sensor electrode used for capacitive sensing. The equalization signal may include a plurality of pulses that are synchronized to be out of phase with a capacitive sensing signal driven on the sensor electrode. For example, as the capacitive sensing signal transitions from a low voltage to a high voltage, the equalization signal transitions from a high voltage to a low voltage. Doing so increases the voltage difference between the electrodes and increases the slew rate of the capacitive sensing signal. In further embodiments, where the input device includes a display device, the equalization signal may be driven onto display electrodes that are used when updating a display.

Claims

1. A processing system for a capacitive sensing device, the processing system comprising:

a first module for the capacitive sensing device, wherein the first module is configured to drive a first electrode with a capacitive sensing signal comprising a plurality of sensing cycles linked by respective voltage transitions; and

a second module for the capacitive sensing device, wherein the second module is configured to drive a second electrode with an equalization pulse during at least one of the voltage transitions, wherein the first electrode is capacitively coupled to the second electrode via the capacitance;

wherein the second electrode is configured to perform at least one of capacitive sensing and display updating and is capacitively coupled to the first electrode, wherein the equalization pulse is out of phase with the capacitive sensing signal such that a voltage change of the equalization pulse is opposite the at least one voltage transition, and wherein a duration of the equalization pulse is less than a duration of one of the plurality of sensing cycles.

2. The processing system of claim 1, wherein the second module is a receiver module configured to receive a resulting signal used for capacitive sensing via the second electrode, the resulting signal is based on, at least in part, the capacitive sensing signal driven on the first electrode.

3. The processing system of claim 1, wherein the first module is configured to measure a change in capacitance between the first electrode and earth ground.

4. The processing system of claim 1, wherein the second module is a display module configured to drive a voltage onto the second electrode when updating an image on a display.

5. The processing system of claim 1, wherein the second module drives a sequence of equalization pulses that at least partially overlap in time with the respective voltage transitions, wherein a respective voltage change of each of the equalization pulses is in a opposite direction of the respective voltage transitions.

6. The processing system of claim 1, wherein the equalization pulse decreases a settling time of the capacitive sensing signal as the capacitive sensing signal changes from a first voltage to a second voltage during the respective voltage transitions.

7. The processing system of claim 1, further comprising a display module configured to drive a voltage onto the first electrode when updating an image on a display.

8. The processing system of claim 7, further comprising:

a first integrated controller comprising the first module, the second module, and the display module.

9. The processing system of claim 7, further comprising:

a first integrated controller comprising the first module and the second module; and

a second integrated controller comprising the display module.

10. The processing system of claim 7, further comprising:

a first integrated controller comprising the first module and the display module;

a second integrated controller comprising the second module.

11. An input device comprising:

a plurality of sensor electrodes that establish a sensing region of the input device;

a processing system coupled to the plurality of sensor electrodes, the processing system is configured to;

drive a first electrode of the plurality of sensor electrodes with a capacitive sensing signal comprising a plurality of sensing cycles linked by respective voltage transitions;

drive a second electrode with an equalization pulse during at least one of the voltage transitions, wherein the second electrode is configured to perform at least one of capacitive sensing and display updating and is capacitively coupled to the first electrode, wherein the equalization pulse is out of phase with the capacitive sensing signal such that a voltage change of the equalization pulse is opposite the at least one voltage transition, and wherein a duration of the equalization pulse is less than a duration of one of the plurality of sensing cycles.

12. The input device of claim 11, wherein the second electrode is one of the plurality of sensor electrodes, and wherein the processing system is configured to receive a resulting signal used for capacitive sensing via the second electrode, the resulting signal is based on, at least in part, the capacitive sensing signal driven on the first electrode.

13. The input device of claim 11, wherein the first module is configured to measure a change in capacitance between the first electrode and earth ground.

14. The processing system of claim 11, wherein second electrode is a display electrode, wherein the processing system is configured to drive a voltage onto the second electrode when updating an image on a display.

15. The input device of claim 11, wherein the processing system is configured to drive a sequence of equalization pulses at least partially overlapping in time with each of the respective voltage transitions, wherein a respective voltage change of each of the equalization pulses is in an opposite direction of the respective voltage transitions.

16. The input device of claim 11, wherein the processing system is configured to drive a voltage onto the first electrode when updating an image on a display.

17. The input device of claim 11, wherein the first and second electrodes are arranged on a same surface.

18. The input device of claim 11, wherein the first electrode is on a different layer than the second electrode, wherein at least a portion of the first electrode overlaps the second electrode.

19. A method of performing capacitive sensing, the method comprising:

driving a capacitive sensing signal onto a first electrode, the capacitive sensing signal comprising a plurality of sensing cycles linked by respective voltage transitions;

driving an equalization pulse onto a second electrode during at least one of the voltage transitions, wherein the second electrode is configured to perform at least one of capacitive sensing and display updating and is capacitively coupled to the first electrode, wherein the equalization pulse is out of phase with the capacitive sensing signal such that a voltage change of the equalization pulse is opposite the at least one voltage transition, and wherein a duration of the equalization pulse is less than a duration of one of the plurality of sensing cycles.

20. The method of claim 19, further comprising receiving a resulting signal via a receiver electrode, the resulting signal is based on, at least in part, the capacitive sensing signal driven on the first electrode.

21. The method of claim 19, further comprising measuring a change in capacitance between the first electrode and earth ground.