[SI-LIST] Re: power planes on adjacentlayers crossing each other
- From: "Orin Laney" <olaney@xxxxxxxxx>
- To: <weirsi@xxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Thu, 10 Jul 2014 15:29:05 -0700
Greetings, Steve.
Key phrase: ridiculous ways. It's a problem I've rarely seen because it is
"truly unusual", and my own designs intuitively avoid such problems. But,
that said, there is no bound on human stupidity and Murphy rules the
universe. There is a certain enhancement of my consulting income from
clients who don't comprehend my advice the first time, or the second, or the
third... Of course, I prefer the ones who get it so quickly they almost
finish my sentences for me, even if the result is shorter gigs. You know
the drill.
Orin
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of steve weir
Sent: Thursday, July 10, 2014 1:56 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: power planes on adjacentlayers crossing each other
Orin, I would be careful about qualifying that blanket statement. There are
well documented case histories where that assumption was applied in somewhat
ridiculous ways with the predictably disastrous results.
Best Regards,
Steve
On 7/10/2014 12:37 PM, Orin Laney wrote:
> No, not a concern. This forum chats a lot about high speed signals
> crossing plane splits, but the various power supplies are not high speed
signals.
> High Sometimes people worry about noise coupling through the small
> common capacitance, but unless your needs are truly unusual, such
> coupling is so small compared to the bypass capacitances that it is of no
consequence.
>
> Note that high speed signals outside of this portion of the stack up
> will see only your ground planes and not be affected by the split
> power planes or their overlapping portions.
>
> Orin
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Ashok Srinivas
> Sent: Thursday, July 10, 2014 12:13 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] power planes on adjacentlayers crossing each other
>
> Hi SI-LIST,
> We are using a 12 layer PCB stack up and have power planes on layer 6
> and layer 7 (just to clarify layers 6 and 7 are not power planes
> completely but its more like a power plane island). These power planes
> on layers 6 and 7 cross each other.
>
> I will use layer 5 to ground the layer 6 power plane and similarly use
> layer
> 8 to ground the layer 7 power plane.
>
> Is this crossing a concern ?if yes why?
>
> Thanks!
> --
> Ashok
>
>
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--
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