[SI-LIST] Re: Decoupling for PLL (continued)
- From: "Michael E. Vrbanac" <vrbanacm@xxxxxxxxxx>
- To: zhang_kun@xxxxxxxxxx
- Date: Mon, 06 Sep 2004 00:32:14 -0500
Zhangkun,
Now your problem is making much more sense to me... and its very common.
Do something about the 333 KHz or fix the PLL filter to handle it or both.
You can decide what is most appropriate for your design.
re: ferrite bead
Of course, it'll do that. However, I think its a distraction for you.
Work the
333 KHz issue. The bead's effective frequency range is likely to be
over 50 MHz
unless it was selected very carefully for < 1 MHz and then its likely
not to be
the same sort of "ferrite". A high frequency bead would be useful for
other purposes
in the same circuit but not for 333 KHz.
Michael E. Vrbanac
Zhangkun wrote:
>Dear all
>Recently, I have done some measurement. It is found that when the
>bead(inductor) is used, the power ground noise at 333KHz from VRM is larger.
>There is some noise near the clock frequency points.
>
>For example, the output clock of PLL is 50MHz. At 50.333MHz and 49.667MHz,
>there is noise, which is in proportion to the noise at 333KHz. Maybe the PLL
>modulates the noise of VRM into the output clock.
>
>Is there any SPICE model for PLL?
>
>Best Regards
>
>Zhangkun
>2004.9.3
>
>
>------------------------------------------------------------------
>To unsubscribe from si-list:
>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
>or to administer your membership from a web page, go to:
>//www.freelists.org/webpage/si-list
>
>For help:
>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>List FAQ wiki page is located at:
> http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>
>List technical documents are available at:
> http://www.si-list.org
>
>List archives are viewable at:
> //www.freelists.org/archives/si-list
>or at our remote archives:
> http://groups.yahoo.com/group/si-list/messages
>Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
>
>
>
>
>
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List FAQ wiki page is located at:
http://si-list.org/wiki/wiki.pl?Si-List_FAQ
List technical documents are available at:
http://www.si-list.org
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
