Re: [SI-LIST] : Fast edges with limited plane capacitance

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From: Larry Smith (ldsmith@lisboa.eng.sun.com)
Date: Fri Mar 17 2000 - 12:56:31 PST


Michael - Looks like we have stirred up another hornets nest. Fun
isn't it? It would be great to meet for lunch, but my schedule is a
nightmare. Maybe we can settle things down by answering the following
question:

Do we get more radiated emissions from:

        a) noisy power planes and structures connected to noisy
           power planes?
           
        b) microstrip transmission lines that are exposed to air
           dielectric somewhere above?
           
The answer to that question will influence the stackup for a product.
The answer will probably depend on the quality of the microstrip
termination and the integrity of the return plane for the microstrip
(do transmission lines run over splits in the plane?).

For most of the projects I work on, this discussion is a moot point.
By jumping to an 8 (or more) layer board, you can have the best of
both worlds.

   s-G-s-s-P-s compromises power plane impedance.
   
   s-s-G-P-s-s compromises shielding.
   
   s-G-P-s-s-G-P-s gives good power plane capacitance and shielding.
                           Compromises cost. No free lunch...

regards,
Larry Smith
Sun Microsystems

        
> From: MikonCons@aol.com
> Date: Fri, 17 Mar 2000 13:51:38 EST
> Subject: Re: [SI-LIST] : Fast edges with limited plane capacitance
> To: si-list@silab.eng.sun.com
> MIME-Version: 1.0
> Content-Transfer-Encoding: 7bit
>
> Larry:
>
> It looks like we are at odds on this one and have perhaps thoroughly confused
> Matt. Perhaps we need to have a confab over lunch to more efficiently
> exchange views. Or maybe even start a monthly roundtable meeting of SI
> Engineers to meet and exchange problems, concepts, and experiences over a
> two-hour lunch. Anyone else interested?
>
> Michael L. Conn
> Owner/Principal Consultant
> Mikon Consulting
>
> *** Serving Your Needs with Technical Excellence ***
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