Methods and circuits for measuring mutual and self capacitance

• US 9,423,427 B2
• Filed: 03/10/2014
• Issued: 08/23/2016
• Est. Priority Date: 02/27/2008
• Status: Active Grant

• Current Assignee: Parade Technologies, Ltd.
• Original Assignee: Parade Technologies, Ltd.
• Inventors: Maharyta, Andriy
• Primary Examiner(s): NGUYEN, HOAI AN D
• Application Number:
  US14/203,145
• Publication Number:
  US 20140266257A1
• Time in Patent Office: 897 Days
• Field of Search: 324/519, 324/600, 324/649, 324/658, 324/686, 702/47, 702/52, 340/545.4, 340/562, 733/350.4, 733/04.C, 735/143.2, 737/18, 737/24, 737/80, 738/623.37, 738/626.2, 73/6, 345/173, 345/174
• US Class Current: 1/1
• CPC Class Codes: G01D 5/24 by varying capacitance
• CPC Class Codes: G01D 5/241 by relative movement of capacitor electrodes
• CPC Class Codes: G01D 5/2412 by varying overlap
• CPC Class Codes: G01D 5/2417 by varying separation
• CPC Class Codes: G01R 17/00 Measuring arrangements involving comparison with a reference value, e.g. bridge
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• CPC Class Codes: G06F 3/016 Input arrangements with force or tactile feedback as computer generated output to the user
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing
• CPC Class Codes: H03K 17/962 Capacitive touch switches

Abstract

In an example embodiment, an apparatus includes a sensing device. The sensing device includes circuitry configured to sense self-capacitance and circuitry configured to sense mutual-capacitance, each configured to detect capacitance values corresponding to whether an object is proximate to a touch screen. The sensing device is configured to measure a first capacitance value using the self-capacitance circuitry during self-capacitance sensing operations and to measure a second capacitance value using the mutual-capacitance circuitry during mutual-capacitance sensing operations.

Claims

1. An apparatus comprising:

a sensing device coupled to a capacitive sense array including a plurality of capacitive sensors, wherein each capacitive sensor of the capacitive sense array includes a respective self capacitance component and a respective mutual capacitance component, and the sensing device further comprises;

self-capacitance circuitry electrically coupled to the respective self capacitance component of each capacitive sensor and configured to perform self-capacitance sensing operations to measure self capacitance of the respective capacitive sensor; and

mutual-capacitance circuitry electrically coupled to the respective mutual capacitance component of each capacitive sensor and configured to perform mutual capacitance sensing operations to measure mutual capacitance associated with the respective capacitive sensor;

wherein both the self-capacitance circuitry and the mutual-capacitance circuitry are coupled to each capacitive sensor by a respective single pair of electrodes associated with the respective capacitive sensor, and configured to detect whether an object is proximate to a touch screen by measuring the self and mutual capacitances of the respective capacitive sensor independently and simultaneously.

2. The apparatus of claim 1, further comprising a capacitive sensor coupled to the sensing device, the capacitive sensor including a first electrode and a second electrode, wherein the first electrode is configured to have a first self-capacitance and the second electrode is configured to have a second self-capacitance, and wherein the first electrode and the second electrode are configured to have mutual capacitance between them.

3. The apparatus of claim 2 wherein, during the self-capacitance sensing operations, the sensing device is configured to measure the first self-capacitance of the first electrode.

4. The apparatus of claim 3, wherein the sensing device further comprises an integration capacitor coupled to the first electrode, wherein the integration capacitor is used to measure the first self-capacitance of the first electrode.

5. The apparatus of claim 2, wherein, during the mutual-capacitance sensing operations, the sensing device is configured to measure the mutual capacitance between the first electrode and the second electrode.

6. The apparatus of claim 1, wherein the sensing device is configured to independently measure self-capacitance values using the self-capacitance circuitry and mutual capacitance values using the mutual-capacitance circuitry.

7. The apparatus of claim 1, wherein the sensing device further comprises a switching system that is configured to selectively switch to the self-capacitance circuitry during the self-capacitance sensing operations and to the mutual-capacitance circuitry during the mutual-capacitance sensing operations.

8. The apparatus of claim 1, wherein the sensing device further comprises a measurement circuit that is coupled to the self-capacitance circuitry and the mutual capacitance circuitry, wherein the measurement circuit is configured to measure self-capacitance values during the self-capacitance sensing operations and to measure mutual capacitance values during the mutual-capacitance sensing operations.

9. A method comprising:

at a sensing device coupled to a capacitive sense array including a plurality of capacitive sensors, wherein each capacitive sensor of the capacitive sense array includes a respective self capacitance component and a respective mutual capacitance component, and the sensing device includes a self-capacitance circuit and a mutual-capacitance circuit;

for each capacitive sensor;

coupling the self-capacitance circuitry to the respective self capacitance component of the respective capacitive sensor via a respective single pair of electrodes associated with the respective capacitive sensor, wherein the self-capacitance circuitry is configured to perform self-capacitance sensing operations to measure self capacitance of the respective capacitive sensor;

coupling the mutual-capacitance circuitry to the respective mutual capacitance component of the respective capacitive sensor via the respective single pair of electrodes associated with the respective capacitive sensor, wherein the mutual-capacitance circuitry is configured to perform mutual capacitance sensing operations to measure mutual capacitance associated with the respective capacitive sensor;

selecting a type of capacitance sensing operation to perform with the self-capacitance circuitry and the mutual-capacitance circuitry; and

in accordance with the selected type of capacitance sensing operation, measuring the self capacitance and the mutual capacitance of the respective capacitive sensor independently and simultaneously.

10. The method of claim 9, wherein the capacitance value corresponds to whether an object is proximate to a touch screen.

11. A system comprising:

a capacitive sense array including a plurality of capacitive sensors, each capacitive sensor including a respective first electrode and a respective second electrode, wherein the first electrode is configured to have a first self-capacitance and the second electrode is configured to have a second self-capacitance, and wherein the first electrode and the second electrode are configured to have mutual capacitance between them;

a sensing device coupled to the capacitive sensor array, wherein the sensing device is coupled to each capacitive sensor by a respective single pair of electrodes associated with the respective capacitive sensor, and configured, for each capacitive sensor of the capacitive sensor array, to;

independently and simultaneously measure the first self-capacitance from the respective capacitive sensor during self-capacitance sensing operations and measure the mutual capacitance from the respective capacitive sensor during mutual-capacitance sensing operations.

12. The system of claim 11, wherein the sensing device comprises self-capacitance circuitry and mutual-capacitance circuitry, each configured to detect whether an object is proximate to the capacitive sensor, wherein the sensing device is further configured to:

perform the self-capacitance sensing operations using the self-capacitance circuitry; and

perform the mutual-capacitance sensing operations using the mutual-capacitance circuitry.

13. The system of claim 12, wherein the sensing device further comprises a measurement circuit that is coupled to the self-capacitance circuitry and the mutual-capacitance circuitry, wherein the measurement circuit is configured to measure self-capacitance values during the self-capacitance sensing operations and to measure mutual capacitance values during the mutual-capacitance sensing operations.

14. The system of claim 12, wherein the sensing device further comprises:

a voltage source configured to output a voltage for use during the self-capacitance sensing operations and the mutual-capacitance sensing operations; and

a switching system configured to selectively couple the voltage to the self-capacitance circuitry or the mutual-capacitance circuitry.

15. The system of claim 11, wherein a first capacitance value measured during the self-capacitance sensing operations corresponds to the first self-capacitance of the first electrode, and wherein a second capacitance value measured during the mutual-capacitance sensing operations corresponds to the mutual-capacitance between the first electrode and the second electrode.

16. The system of claim 11, wherein the sensing device further comprises an integration capacitor coupled to the first electrode, wherein the integration capacitor is used to measure the first self-capacitance of the first electrode.