From: Larry Miller ([email protected])
Date: Fri Oct 29 1999 - 06:55:07 PDT
ken, I'm sure you have something to contribute, but most of the time your
postings consist only of the message to which you are responding. Maybe you
need to get a bit of help with your e-mail program...
Larry Miller
At 07:24 AM 10/28/99 -0700, you wrote:
>
>----- Original Message -----
>From: Pat Zabinski <[email protected]>
>To: <[email protected]>
>Sent: Thursday, October 28, 1999 5:25 AM
>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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>
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