Re: [SI-LIST] : Bulk Caps -> Inductor? -> Plane

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From: Silvio ORSI (Silvio.Orsi@cern.ch)
Date: Fri Apr 14 2000 - 08:33:06 PDT


What worries me about using bulk capacitors with different capacitance
in parallel as in the picture you sent is well described in the following
article:
http://www.cypress.com/pub/appnotes/decouple.pdf
(look expecially picture 5 on page 3)

I hope this helps!
Regards,
        Silvio

On Tue, 11 Apr 2000, mjs wrote:

>
> I am not sure if the list accepts attachments, but here goes.
> If the attachment is stripped by the listserve, please find
> it visible at www.enteract.com/~mjs/induct.gif (16k)
> --
>
> The attached gif show a snip from a schematic currently in layout.
>
> The transformer shows the secondary of the SMPS, connected
> to a whole mess of bulk capacitance, especially on +5V net.
>
> Please note L202 series inductor inserted between the bulk capacitance and
> the connection to the power plane. This worries me most. There seems to
> be no valid reason to stuff series inductance between the bulk and the
> plane. Further, all the local ceramic IC pin bypass will also have to
> suck current through that same inductor. Seems like a terrible idea to
> me. Comments welcome.
>
> Matt Stanik
> Sr. PCB Design Eng.
> Charles Industries, Ltd.
>

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