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

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From: Doug McKean (dmckean@corp.auspex.com)
Date: Wed Sep 13 2000 - 14:08:13 PDT


Boris Yost wrote:
>
> 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?

Without knowing anything other than
what you've presented here - yes.

How much overkill? Don't know.

I'm assuming this thing is an FCC Class B device.

- Doug

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