RE: [SI-LIST] : Bead-choking the power supply--everywhere!

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From: Bill Owsley ([email protected])
Date: Wed Sep 13 2000 - 16:38:25 PDT


I'll 'see' Mike - overkill, and raise him one. Just use the ferrites. The
caps bypass the noise into the ground planes making them noisy, polluting
everything else... <grin> and besides, you can't get enough caps anyway.

At 02:40 PM 09/13/2000 -0500, Mayer, Mike wrote:
>I though "one capacitor per IC" was overkill! I think caps are already on
>allocation, so good luck.
>
>============================================================================
>=
>Mike Mayer Artesyn Communication Products, Inc
>Senior Hardware Design Engineer Madison, WI
>[email protected] http://www.artesyncp.com
>============================================================================
>=
>
>
> > -----Original Message-----
> > From: Boris Yost [mailto:[email protected]]
> > Sent: Wednesday, September 13, 2000 1:59 PM
> > To: [email protected]
> > Subject: [SI-LIST] : Bead-choking the power supply--everywhere!
> >
> >
> > Dear list members:
> >
> > I'm looking at a design right now--portions of which
> > were inspired by an
> > "EMI expert". Specifically, instead of ordinary decoupling
> > practice, there
> > are filters with a capacitor on each side of a ferrite
> > bead...individually...for each and every device on the board.
> > Almost all of
> > the devices have "CMOS" outputs--the output goes to the high
> > rail. Almost
> > all of the devices are fully static logic. The system is a
> > digital video
> > display, it has one input, and the board output doesn't leave
> > the box. 80%
> > of the board, and everything doing real work, operates
> > synchronously to the
> > input clock.
> > Is this "decoupling" scheme overkill, useful, or a
> > disaster waiting to
> > happen?
> >
> > Best regards,
> > Boris Yost
> >
> > P.S. Order ferrite beads! Now! They will soon be on-allocation!
> >
> >
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> >
>
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----------------------------
Bill Owsley, [email protected]
919) 392-8341

TMBU Compliance
Cisco Systems
7025 Kit Creek Road
POB 14987
RTP. NC. 27709

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