Re: [SI-LIST] : quad offset stripline?

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From: Rachild Chen (rachel.chen@huawei.com.cn)
Date: Fri Oct 29 1999 - 18:47:03 PDT


Hi every specialist,

I'm do some simulations with Hspice too.Who can tell me how to simulate the SSN eye diagram
in Hspice?

Regards,
Rachild

Bradley S Henson wrote:

> I see you're using 'W' element t-line models, so I guess your using HSPICE for
> generating the eye diagrams too???
>
> To answer your question, I've done a similer stackup under duress, and it wasn't
> a production board. I think it can be done with the type of rigorous engineering
> you appear to be doing. I'll suggest adding extra margin for inter-layer
> effects: When we did inter-layer SSO we saw more interaction than
> predicted...the z-axis and diagonal coupling of lots of bus lines to a victim on
> another layer appeared to have more of a cumulative impact than we expected.
> I've bounced around jobs a couple times in the last 2 years so I no longer have
> the writeup, but I think I've hit the high/low points.
>
> Luck,
> Brad Henson, Raytheon
>
> "Pat Zabinski" <zabinski.patrick@mayo.edu> on 10/28/99 05:25:48 AM
>
> Please respond to si-list@silab.eng.sun.com
>
>
>
>
>
>
>
> To: si-list@silab.eng.sun.com
>
> cc: (bcc: Bradley S Henson/RWS/Raytheon/US)
>
>
>
> Subject: [SI-LIST] : quad offset stripline?
>
>
> On a rather route-intense design we're working on, we are trying
> to squeeze in as many signal layers as we possibly can in
> a given overall board thickness. We've been playing around
> with different scenarios with different board vendors for
> the past month, and what we've come up with is a layer stackup
> based on "quad offset stripline", meaning:
>
> ---------------------- plane
> ---- signal-T
> ---- signal-S
> ---- signal-Y
> ---- signal-X
> ---------------------- plane
>
> X is horizontal, Y is vertical, S is 45, and T is 135. We have
> buried vias between S & T and between X & Y. For a particular
> signal, we only route on orthogonal layer-pairs.
>
> We've been analyzing this for a short time now, and it looks like
> it might work out for our application. But before we take it too
> far, I'd like to get input from folks on potential gotchas that
> I should be concerned with.
>
> As background, we have:
>
> * designed a line width for the respective layers to obtain
> our target impedance (50 ohms).
>
> * ran SSN eye diagram simulations of multiple signals
> on one layer at a time to determine the minimum
> trace-pitch for that layer.
>
> * using the minimum-pitch per layer, mutual capacitance
> and inductance of the crossovers (taking into account
> the relative angle of the traces), and a W-element
> representation of lines on each of the four
> layers, we ran an SSN eye diagram simulation of random
> signals on all four layers to determine the effects
> of the mutual parasitics from the other layers.
>
> So far, if we keep the trace pitch wide enough, this seems to
> work just fine. However, I'd like input of other areas we
> should look at.
>
> Any ideas? Has anyone used this sort of thing in the multi-100's
> of MHz (<500 psec Tr) regime? Am I missing something?
>
> Thanks,
> Pat
>
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