[SI-LIST] Re: PCB Gnd discontinuity on simulation software
- From: <Wolfgang.Maichen@xxxxxxxxxxxx>
- To: <scott@xxxxxxxxxxxxx>, <gpfitzgerald2000@xxxxxxxxx>
- Date: Thu, 8 Mar 2012 07:35:51 +0000
Ettore,
actually a full 3D field solver may be a bit overkill; any decent 2.5D (planar)
field solver can give pretty accurate answers for split ground planes, and
makes model creation easier for an occasional user. As a rule of thumb, routing
single ended lines over a split in the reference plane sets you up for a lot of
trouble unless both the frequencies involved are very low and the signal rise
times are very long. Things are much better for diff pairs which can tolerate
breaks much better as long as the two lines of the pair are not spaced too far
from each other (1-3 line widths is usually fine with typical PCB dimensions).
But only a field solver can give a good answer for a specific case. One place
to start could be the free version of Sonnet, called Sonnet Lite - can actually
handle such situations and I've used it successfully myself to simulate split
grounds. (I'm not affiliated with Sonnet in any way, I'm just a user of Sonnet
Lite). One thing to watch out when simulating _single ended_ lines with such a
solver are boundary conditions - e.g. Sonnet encloses the model in a virtual
metal box, so if you are not careful this box can short your ref planes
together, resulting in unrealistically good performance of such a split.
Wolfgang
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Scott McMorrow
Sent: Thursday, March 08, 2012 12:04 AM
To: gpfitzgerald2000@xxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx; steve weir
Subject: [SI-LIST] Re: PCB Gnd discontinuity on simulation software
Greg
I'm not sure why you're posting this. Since you've not provided any
meaningful information, I'd have to assume that you are
advertising/marketing yourself, or this EM solver that cannot be mentioned
by name. If you are going to advertise/market in this way, please at least
have the decency to provide some information that could further the
discussion and might be helpful to designers.
Scott
--
Scott McMorrow
Teraspeed Consulting Group LLC
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(401) 284-1827 Business
(401) 284-1840 Fax
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Teraspeed(r) is the registered service mark of
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On Wed, Mar 7, 2012 at 5:34 PM, Gregory Fitzgerald <
gpfitzgerald2000@xxxxxxxxx> wrote:
> Ettore:
>
> As a consultant, I have worked with some clients that had access to new
> FAST 2.5D solvers that accurately account for the situation mentioned below
> (signals crossing over split planes). Unfortunately, this work was under
> an NDA so I cannot provide more information. What I can state is that the
> products are from a ~3 year old new start up that is working with a few,
> large teaching customers before they roll out a product to the mass market.
>
> Product was a little immature but was quickly maturing into a full SI/PI
> platform. It is different and better approach to current products on the
> market.
>
> Greg
> --- On Fri, 2/24/12, steve weir <weirsi@xxxxxxxxxx> wrote:
>
>
> From: steve weir <weirsi@xxxxxxxxxx>
> Subject: [SI-LIST] Re: PCB Gnd discontinuity on simulation software
> To: si-list@xxxxxxxxxxxxx
> Date: Friday, February 24, 2012, 7:30 AM
>
>
> Ettore, your picture did not come through as the SI-list does not
> support attachments.
>
> I do not believe that present versions of Hyperlynx account for signals
> crossing plane splits. If I am wrong, I am sure the Mentor guys will
> chime in. In order to evaluate those kinds of effects accurately, a
> full-wave solver is the best way to go. However, I will tell you right
> now that you don't need a full wave tool to accurately predict that you
> are setting yourself up for EMI headaches by introducing such a
> discontinuity. You should really do what you can to maintain a
> contiguous transmission path.
>
> Steve.
> On 2/24/2012 2:29 AM, ruscino wrote:
> > Content-Type: text/plain; charset=ISO-8859-15; format=flowed
> > Content-Transfer-Encoding: 7bit
> > Hi all, in my circuit there are lvds nets that are on gnd shape
> > (microstrip topology).
> > These nets crossing also a circuit area where there is not the gnd shape.
> > When I simulate this circuit on simulation software like Hyperlynx
> > take the software into account this gnd discontinuity?
> > See the picture in attach, please.
> >
> > Thanks a lot
> > Ettore
> >
> >
> >
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>
> --
> Steve Weir
> IPBLOX, LLC
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