Low-power switch state detection circuit and method and mobile telephone device incorporating the same

• US 20060255812A1
• Filed: 05/06/2005
• Published: 11/16/2006
• Est. Priority Date: 05/06/2005
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Agere Systems Incorporated (Broadcom, Inc.)
• Inventors: Verney, Richard, Martin, David G., Walden, Robert W.
• Granted Patent: US 7,834,634 B2
• Time in Patent Office: Days
• US Class Current: 324/609
• CPC Class Codes: H01H 9/167 Circuits for remote indication
• CPC Class Codes: H03K 17/18 Modifications for indicating state of switch

Abstract

A circuit for, and method of, detecting a signal level on a node and a mobile telephone device incorporating the circuit or the method. In one embodiment, the circuit includes: (1) a switch coupled between a voltage source and the node, (2) a pulse generator coupled to the switch and configured to generate a pulse to control the switch and (3) a detection circuit coupled to the node and configured to detect a signal level at the node on closure of the switch.

Claims

1. A circuit for detecting a signal level on a node, comprising:

a switch coupled between a voltage source and said node;

a pulse generator coupled to said switch and configured to generate a pulse to control said switch; and

a detection circuit coupled to said node and configured to detect a signal level at said node on closure of said switch.

2. The circuit as recited in claim 1 further comprising a further switch connected between said node and a ground potential, said detection circuit being configured to detect a level at said node determined by said state of said further switch.

3. The circuit as recited in claim 1 wherein said pulse generator is further configured to control said detection circuit.

4. The circuit as recited in claim 3 wherein said pulse generator is configured to open and close said switch, wherein said detection circuit is enabled on closure of said switch.

5. The circuit as recited in claim 1 wherein said detection circuit is configured to detect a signal at said node responsive to a stable signal at said node on a series of successive switch closures.

6. The circuit as recited in claim 1 wherein said detection circuit is configured to compare a current signal level at said node to a previous signal level to detect a transition at said node.

7. The circuit as recited in claim 6 wherein said transition is responsive to closure of a further switch connected between said node and a ground potential.

8. The circuit as recited in claim 1 further comprising a further switch connected between a further bias voltage and said node.

9. The circuit as recited in claim 8 wherein said further switch is a control switch for said device.

10. The circuit as recited in claim 9 wherein said control switch is an on-off switch for said device.

11. The circuit as recited in claim 8 wherein said switch and said further switch are controlled such that when one is closed said other is open.

12. The circuit as recited in claim 8 wherein said switch is disabled when said further switch is closed, and said switch is enabled when said further switch is open.

13. The circuit as recited in claim 8 further comprising a still further switch connected between said node and said ground potential, said detection circuit being configured to detect a signal level at said node determined by said state of said still further switch.

14. The circuit as recited in claim 13 wherein said further switch is a control switch of said device, and said detection circuit is configured to detect said state of said still further switch, said further switch being closed to provide a bias voltage to said detection circuit when said control switch is open.

15. The circuit as recited in claim 14 wherein said device is a headset and said further switch is a push-button of said headset.

16. The circuit as recited in claim 1 wherein said circuit is contained within a mobile telephone device.

17. The circuit as recited in claim 1 wherein said circuit is contained within a headset of an electronic device.

18. A method of detecting a signal transition, comprising:

periodically switching a bias voltage to a node;

monitoring said node; and

detecting a change in said state of said node on switching of said bias voltage.

19. The method as recited in claim 18 further comprising selectively connecting said node to a ground potential, said detecting comprising detecting a signal level at said node determined by said state of selective connection.

20. The method as recited in claim 18 wherein said detecting comprises detecting a signal at said node responsive to a stable signal at said node on a series of successive switch closures.

21. The method as recited in claim 18 further comprising comparing a current signal level at said node to a previous signal level to detect a transition at said node.

22. The method as recited in claim 21 wherein said transition is detected responsive to closure of a further switch connected between said node and a ground potential.

23. The method as recited in claim 18 further comprising providing a further switch between a further bias voltage and said node.

24. The method as recited in claim 23 further comprising controlling said switch and said further switch such that when one is closed said other is open.

25. The method as recited in claim 23 further comprising:

disabling said switch when said further switch is closed; and

enabling said switch when said further switch is open.

26. The method as recited in claim 23 further comprising connecting a still further switch between said node and said ground potential, said detecting a signal level at said node being determined by said state of said still further switch.

27. The method as recited in claim 26 further comprising detecting said state of said still further switch, said further switch being closed to provide a bias voltage to said detection circuit when said control switch is open.