RE: [SI-LIST] : Ferrite Beads

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From: Steve Ash (Steve@sedonanetworks.com)
Date: Sat Nov 18 2000 - 01:46:04 PST


I'm guessing this would not apply if your WHOLE schematic (CCA) plugged into
a backplane, say, such that you were getting your power from the backplane
as well as transmitting and receiving other single-ended (ground referenced)
signals to/from other CCAs on the same backplane. I would think you would
not want a ferrite in the Ground path on a CCA in this scenario.

Stephen Ash
Hardware Designer
Sedona Networks
308 Legget Drive,
Kanata, Ontario
K2K 1Y6

Tel: (613) 599-1600 ext. 5062
Fax: (613) 599-3040
Mailto:steve@sedonanetworks.com

-----Original Message-----
From: Michael Nudelman [mailto:mnudelman@tellium.com]
Sent: Thursday, November 16, 2000 3:50 PM
To: Dilpreet Saini
Cc: 'marcgodbout@auranetinc.com'; si-list@silab.eng.sun.com
Subject: Re: [SI-LIST] : Ferrite Beads

You should keep at least one common reference signal solid; otherwise any
perturbance across the Ferrite (and it will
be; that's why it is there) will be superimposed on your signals.

If you use it to reject noise from power supply and your WHOLE schematic is
behind the ferrite - it is OK and even
desirable; if the ferrite is in between two parts of the sch. that are
supposed to share common GND - bad idea.

Dilpreet Saini wrote:

> Hi Marc,
> Can you please comment a little bit more on Why would a ferrite in
series with GND cause the ground bounce.
>
> regards,
> Dilpreet
>
> -----Original Message-----
> From: marcgodbout@auranetinc.com [mailto:marcgodbout@auranetinc.com]
> Sent: Thursday, November 16, 2000 4:41 AM
> To: Dilpreet Saini; si-list@silab.eng.sun.com
> Subject: RE: [SI-LIST] : Ferrite Beads
>
> >From experience, a ferrite in series with GND will cause a ground bounce
on
> the board. If you're using DC coupled signals to other circuits in the
> system, these signals will see their reference point change.
>
> -Marc Godbout
>
> > -----Original Message-----
> > From: Dilpreet Saini [mailto:DSAINI@altera.com]
> > Sent: Wednesday, November 15, 2000 4:45 PM
> > To: SI List (E-mail)
> > Subject: [SI-LIST] : Ferrite Beads
> >
> >
> > Hi all,
> > In the past I have used ferrite beads for transient and
> > parasitic suppression of the supply (VCC) coming into the
> > board. So far I have never used ferrite beads in series with
> > the GND trace/plane. I was wondering do any of you have any
> > experience using ferrite beads in that scenario.
> > Thanks in advance for your help.
> >
> > regards,
> > Dilpreet
>
>
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