Noise elimination in a USB codec

• US 6,216,052 B1
• Filed: 10/23/1996
• Issued: 04/10/2001
• Est. Priority Date: 10/23/1996
• Status: Expired due to Term

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: Advanced Micro Devices, Inc.
• Inventors: Gulick, Dale
• Primary Examiner(s): Harvey, Minsun Oh
• Application Number:
  US08/740,017
• Time in Patent Office: 1,630 Days
• Field of Search: 381/94, 381/94.5, 381/110, 381/120, 381/104, 381/106-107, 700/94, 713/300
• US Class Current: 700/94
• CPC Class Codes: H03F 1/0211 with control of the supply voltage or current

Abstract

A controller for a powered loudspeaker including a bus monitor configured to monitor a bus for activity and a click suppression unit coupled to the bus monitor and configured to control speaker volume by ramping the volume down if an absence of data on the bus is detected, and restoring the volume once bus activity begins again. In this manner, undesired clicks and hisses upon power up and power down are minimized.

Claims

1. A bus controller comprising:

an interface for coupling said bus controller to a bus and providing signals to and from said bus;

a bus monitor coupled to said interface and configured to receive signals on said bus and to monitor said bus for the presence of clock activity, audio data, or errors in said audio data; and

a suppression unit coupled to said bus monitor and configured to control volume of a powered loudspeaker on said bus responsive to an indication from said bus monitor of an absence of said clock activity, said audio data, or a presence of said errors in said audio data on said bus, wherein said suppression unit is configured to gradually ramp said volume of said powered loudspeaker from a first predetermined level to a second predetermined level responsive to said indication of an absence of said clock activity, said audio data, or a presence of said errors in said audio data on said bus; and

wherein said suppression unit is configured to turn off power to said powered loudspeaker after said volume of said powered loudspeaker has been adjusted to said second predetermined level;

wherein said suppression unit is configured to restore said power to said powered loudspeaker a predetermined time after said power has been turned off or upon said bus monitor detecting the presence of said clock activity, said audio data, or the absence of said errors on said bus;

said suppression unit is further configured to ramp said volume of said powered loudspeaker from said second predetermined level to said first predetermined level after said power has been restored to said powered loudspeaker.

2. The bus controller as recited in claim 1 wherein said bus is a universal serial bus.

3. A speaker controller, comprising:

a bus monitor adapted to receive signals on a bus coupled to said bus monitor, wherein said bus monitor is configured to monitor said bus and to indicate on a control signal a condition selected from the group consisting of a failed cyclic redundancy checksum (CRC) of said signals on said bus, random noise audio data, and an aberrational DC voltage level; and

a suppression unit coupled to said bus monitor to receive said control signal and configured to control volume of a powered loudspeaker coupled to said bus, wherein said suppression unit is responsive to said control signal to lower said volume according to said condition.

4. The speaker controller as recited in claim 3, wherein said bus comprises a Universal Serial Bus (USB).

5. The speaker controller as recited in claim 3, wherein said bus monitor is further configured to monitor said bus for activity and to provide a control signal indicating detection of bus activity below a predetermined threshold for a predetermined period of time, and wherein said suppression unit is configured to lower said volume in response to said control signal indicating detection of bus activity below a predetermined threshold for a predetermined period of time.

6. The speaker controller as recited in claim 5, wherein the speaker controller shuts off power to said powered loudspeaker after said volume is lowered in response to bus activity below said predetermined threshold for said predetermined period of time.

7. The speaker controller as recited claim 6, wherein said bus monitor continues to monitor said bus after power to said powered loudspeaker has been shut off due to low bus activity, and wherein power is restored to said powered loudspeaker upon detection of bus activity and said suppression unit raises said volume after power has been restored.

8. A speaker controller comprising:

a bus monitor adapted to receive signals on a bus coupled to said bus monitor, wherein said bus monitor is configured to monitor audio data on said bus and to provide a control signal in response to detecting the presence of data errors in the audio data, wherein the control signal indicates the presence of data errors in the audio data; and

a suppression unit coupled to said bus monitor to receive said control signal and configured to control volume of a powered loudspeaker coupled to said bus, wherein said suppression unit is responsive to said control signal to lower said volume.

9. The speaker controller as recited in claim 8, wherein said bus comprises a Universal Serial Bus.

10. The speaker controller as recited in claim 8, wherein said data errors comprise a failed cyclic redundancy checksum (CRC).

11. The speaker controller as recited in claim 8, wherein said bus monitor is further configured to monitor said bus for an absence of a predetermined activity on said bus and indicate the absence on said control signal, wherein said suppression unit is responsive to said control signal to lower said volume according to the absence of said predetermined activity on said bus.

12. The speaker controller as recited in claim 11, wherein said predetermined activity is clock activity or audio data.

13. The speaker controller as recited in claim 11, wherein said suppression unit is configured to gradually ramp said volume from a first predetermined level to a second predetermined level responsive to said control signal.

14. The speaker controller as recited in claim 13, wherein said suppression unit is configured to turn off power to said powered loudspeaker after said volume has been adjusted to said second predetermined level.

15. The speaker controller of claim 14, wherein said suppression unit is configured to restore power to said powered loudspeaker a predetermined time after said power has been turned off.

16. The speaker controller as recited in claim 15, wherein said suppression unit is configured to ramp said volume from said second predetermined level to said first predetermined level after said power has been restored to said powered loudspeaker.

17. The speaker controller as recited in claim 14, wherein said suppression unit is configured to restore power to said powered loudspeaker upon said bus monitor detecting the presence of a second predetermined activity.

18. The speaker controller as recited in claim 17, wherein said suppression unit is configured to ramp said volume from said second predetermined level to said first predetermined level after said power has been restored to said powered loudspeaker.

19. The speaker controller as recited in claim 8, further including a high pass filter coupled to said bus monitor and configured to remove DC components from an output signal to an amplifier for said powered loudspeaker.