Re: [SI-LIST] : XTK multiboard simulation using amp spice connector models.........

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From: Georg Ramsch (georg.ramsch@po.uni-stuttgart.de)
Date: Thu Dec 02 1999 - 02:03:51 PST


Hello, Michael !

Well, if you have to do simulation, a lot of patience and time is required to
find
a reality-related result. One solution: try to get SPICE-models of the same
connector from (an)other
vendor(s) and try to compare. Connectors of the same type should not have big
differences! (if anybody objects, please let me know! I am ready to learn!)

Rules of thumb for your problem could be (solution not on simulation side):
1) is the pinning of the connector already fixed or are you able to change it if
SI-issues require it?
   Is the board-to-board interconnect a Futurebus-like pinning?
   If it is more Futurebus-like, so GND-bounce issues should not cause trouble.
   In many systems the GND-bounce caused by the GND-loop of interconnects
(connectors) between cards
   is the most critical.
2) Crosstalk-analysis on databuses should be limited to the critical nets
(protocol signals: reset, ack, datastrobe,
   address-strobe and so on). The crosstalk through coupling from neighbour
lines decreases fast with the distance.
   On a databus (backplane with daughtercards, 30mm slotpitch assumed, 2mm
metric connectors), you described,
   the coupling from neighbours to a victim-line may be less than 3-5%, if the
backplane is designed properly.
   Rest of the noise you see may be reflections from terminations, GND-bounce
from GND-loops or Vcc-drop from Vcc-loops.
   For a rough crosstalk-simulation on a given victim line a 5-conductor
approach may be sufficient.
   (victim line + 2 neighbours from left and right, others do not contribute
much).

So thats my "Zwei Pfennig" of knowledge.

Regards

Georg

"Greim, Michael" schrieb:
>
> Hello SI List,
>
> I am continuing my investigation of XTK and have run into
> a bit of a road block that I thought you might be able to help me with.
> I have a desire to perform a multi-board system simulation where my
> board to board interconnect is a standard 2 mm HM connector that
> is used and supported by lots of folks. I have an AMP MLM for the
> connector and would prefer not to fill my day modifying spice decks.
> My feedback from folks to date has been that 'ya can't get there from
> here', unless of course I would like to re-write the model myself for
> use within XTK.
>
> I know that alot of folks in telecom are using this connector
> and are probably using XTK. What are my options? Any good?
> Thanks for the help.
>
> Best Regards,
>
> Michael Greim
>
> And all this science they don't understand
> It's just my job six days a week.....
>
> The time is gone, The email's over, thought I'd
> something more to say.........
>
> Michael C. Greim Consulting Engineer
> Mercury Computer Systems, Inc email: mgreim@mc.com
> 199 Riverneck Road V: 978-256-0052/x1607
> Chelmsford, MA 01824-2820 F: 978-256-4778
>
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