SYSTEM AND METHOD FOR MEASURING A CAPACITANCE AND SELECTIVELY ACTIVATING AN INDICATING TRANSDUCER

• US 20100045310A1
• Filed: 08/20/2008
• Published: 02/25/2010
• Est. Priority Date: 08/20/2008
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: BETANCOURT, Rafael
• Granted Patent: US 8,058,884 B2
• Time in Patent Office: Days
• US Class Current: 324/686
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: H03K 17/955 using a capacitive detector
• CPC Class Codes: H03K 2217/960785 with illumination

Abstract

Systems and methods for sensing capacitances that are applicable to proximity sensor devices are provided. The systems and methods provide decreased implementation costs by reducing the number of output terminals required. Specifically, the systems and methods for sensing capacitances provide the ability to selectively activate indicating transducers, such as LEDs, with the same output terminals used for sensing capacitances. This reduces the need for additional, dedicated output terminals for activating the indicating transducers. As such, the system and method provides for efficient use of resources in proximity sensor devices.

Claims

1. A capacitive sensor comprising:

a first sensor electrode coupled to a first terminal;

a second sensor electrode coupled to a second terminal;

a first driver circuit coupled to the first terminal and a second driver circuit coupled to the second terminal, where in a first mode the first driver circuit and the second driver circuit are configured to drive the first terminal and the second terminal to substantially equal levels of electrical potential for sensing capacitances associated with the first sensor electrode and the second sensor electrode, and where in a second mode the first driver circuit and the second driver circuit are configured to drive the first terminal and the second terminal to first substantially different levels of electrical potential for activating an indicating transducer that is capable of being coupled between the first terminal and the second terminal.

2. The capacitive sensor of claim 1 wherein the indicating transducer is selected from the group consisting of a light emitting diode (LED) and a piezoelectric device.

3. The capacitive sensor of claim 1 where in a third mode the first driver circuit and the second driver circuit are configured to drive the first terminal and the second terminal to second substantially different levels of electrical potential for activating a second indicating transducer that is capable of being coupled between the first terminal and the second terminal.

4. The capacitive sensor of claim 3 where the second substantially different levels of electrical potential have a polarity different from the first substantially different levels of electrical potential.

5. The capacitive sensor of claim 1 further comprising a first sensor circuit coupled to the first driver circuit and configured to measure charge transferred to the first sensor electrode during the first mode, and further comprising a second sensor circuit coupled to the second driver circuit and configured to measure charge transferred to the second sensor electrode during the first mode.

6. The capacitive sensor of claim 5 wherein the first sensor circuit comprises a first current integrator to measure charge transferred to the first sensor electrode during the first mode, and wherein the second sensor circuit comprises a second current integrator to measure charge transferred to the second sensor electrode during the first mode.

7. The capacitive sensor of claim 5 wherein the first sensor circuit comprises a first voltage integrator to measure charge transferred to the first sensor electrode during the first mode, and wherein the second sensor circuit comprises a second voltage integrator to measure charge transferred to the second sensor electrode during the first mode.

8. The capacitive sensor of claim 1 wherein the first driver circuit and the second driver circuit are configured to drive the first terminal and the second terminal to substantially equal levels of electrical potential using alternating waveforms that are in phase.

9. The capacitive sensor of claim 1 wherein the first driver circuit and the second driver circuit are configured to drive the first terminal and the second terminal to substantially different levels of electrical potential using alternating waveforms that are out of phase.

10. An apparatus comprising:

an LED having a first node and a second node;

a first capacitive sensor electrode;

a second capacitive sensor electrode;

a proximity sensor controller having a first output terminal and a second output terminal, the first output terminal coupled the first node of the LED and the first capacitive sensor electrode, the second output terminal coupled to the second node of the LED and the second capacitive sensor electrode, the proximity sensor controller further comprising;

a first driver circuit coupled to the first output terminal, the first driver circuit configured to drive the first output terminal;

a first sensing circuit coupled to the first driver circuit, the first sensing circuit configured to measure charge transferred to the first electrode to determine a first capacitance associated with the first sensor electrode;

a second driver circuit coupled to the second output terminal, the second driver circuit configured to drive the second output terminal;

a second sensing circuit coupled to the second driver circuit, the second sensing circuit configured to measure charge transferred to the second sensor electrode to determine a second capacitance associated with the second sensor electrode; and

where in a first mode for measuring the first capacitance and the second capacitance, the first driver circuit and the second driver circuit are configured to drive the first output terminal and the second output terminal to substantially equal levels of electric potential, and where in a second mode for activating the LED, the first driver circuit and the second driver circuit are configured to drive the first output terminal and the second output terminal to substantially different levels of electric potential.

11. A method comprising:

applying substantially equal levels of electric potential to a first output terminal and a second output terminal for measuring a first capacitance associated with a first electrode coupled to the first output terminal and measuring a second capacitance associated with a second electrode coupled to the second output terminal; and

applying a first set of substantially different levels of electric potential to the first output terminal and the second output terminal for activating an indicating transducer coupled between the first output terminal and the second output terminal.

12. The method of claim 11 wherein the indicating transducer indicating transducer is selected from the group consisting of a light emitting diode (LED) and a piezoelectric device.

13. The method of claim 11 further comprising:

applying a second set of substantially different levels of electric potential to the first output terminal and the second output terminal for activating a second indicating transducer coupled between the first output terminal and the second output terminal.

14. The method of claim 13 where the second set of substantially different levels of electrical potential have polarities different from the first set of substantially different levels of electrical potential.

15. The method of claim 11 further comprising:

measuring charge transferred to the first electrode during the applying substantially equal levels of electric potential to the first output terminal and the second output terminal; and

measuring charge transferred to the second electrode during applying substantially equal levels of electric potential to the first output terminal and the second output terminal.

16. The method of claim 15 wherein the measuring charge transferred to the first electrode comprises performing a first current integration, and wherein the measuring charge transferred to the second electrode comprises performing a second current integration.

17. The method of claim 15 wherein the measuring charge transferred to the first electrode comprises performing a first voltage integration, and wherein the measuring charge transferred to the second electrode comprises performing a second voltage integration.

18. The method of claim 11 wherein the applying substantially equal levels of electric potential to a first output terminal and a second output terminal comprises applying alternating waveforms that are in phase.

19. The method of claim 11 wherein the applying substantially different levels of electric potential to the first output terminal and the second output terminal comprises applying alternating waveforms that are out of phase.

20. An apparatus comprising:

an indicating transducer including a first node and a second node;

a first capacitive sensor electrode;

a second capacitive sensor electrode;

a first driver circuit coupled to a first terminal and a second driver circuit coupled to a second terminal, the first terminal coupled the first node of the indicating transducer and the first capacitive sensor electrode, the second terminal coupled to the second node of the indicating transducer and the second capacitive sensor electrode, where in a first mode the first driver circuit and the second driver circuit are configured to drive the first terminal and the second terminal to substantially equal levels of electrical potential for sensing capacitances associated with the first sensor electrode and the second sensor electrode, and where in a second mode the first driver circuit and the second driver circuit are configured to drive the first terminal and the second terminal to first substantially different levels of electrical potential for activating the indicating transducer.

21. The apparatus of claim 20 further comprising a second indicating transducer including a first node and a second node, wherein the first node of the second indicating transducer is coupled to the first terminal, and wherein the second node of the second indicating transducer is coupled to the second node, and where in a third mode the first driver circuit and the second driver circuit are configured to drive the first terminal and the second terminal to second substantially different levels of electrical potential for activating the second indicating transducer.

22. The apparatus of claim 21 where the second substantially different levels of electrical potential have a polarity different from the first substantially different levels of electrical potential.

23. The apparatus of claim 20 further comprising a first sensor circuit coupled to the first driver circuit and configured to measure charge transferred to the first sensor electrode during the first mode, and further comprising a second sensor circuit coupled to the second driver circuit and configured to measure charge transferred to the second sensor electrode during the first mode.

24. The apparatus of claim 20 wherein the first driver circuit and the second driver circuit are configured to drive the first terminal and the second terminal to substantially equal levels of electrical potential using alternating waveforms that are in phase, and wherein the first driver circuit and the second driver circuit are configured to drive the first terminal and the second terminal to substantially different levels of electrical potential using alternating waveforms that are out of phase.