RE: [SI-LIST] : 2.5Gbps across a backplane?

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From: Heard, Chris ([email protected])
Date: Wed Oct 11 2000 - 11:32:48 PDT


I support Vinu's advice. If the connector is loosely coupled or not coupled
at all, then the traces on the backplane should be layed out the same way.

Chris

-----Original Message-----
From: Vinu Arumugham [mailto:[email protected]]
Sent: Wednesday, October 11, 2000 12:41 PM
To: Michael Nudelman
Cc: Todd Derego; [email protected]
Subject: Re: [SI-LIST] : 2.5Gbps across a backplane?

Broadside coupling usually means significant coupling between the signal
conductors of the differential pair. However, many backplane connectors may
have
little coupling between the signals of a differential pair.

For optimal performance, the type of coupling used on the board may have to
be
compatible with the type of coupling in the connector.

Thanks,
Vinu

Michael Nudelman wrote:

> Todd:
>
> First, do not use FR-4.
> Try something else. We do, and it works without equalization. And the
backplane
> is huge. The traces' runs are up to few feet. Also try to use broadside
> coupling; if your skin losses are high, this helps a bit.
>
> Mike.
>
> Todd Derego wrote:
>
> > I'm working to take a present 1.25Gbps backplane to 2.5Gbps or
> > faster. Any thought on transceivers with preemphasis and/or adaptive
> > equalization to help get 2.5Gbps or better across a long FR4 backplane?
The
> > eye looks pretty collapsed at 2.5Gbps but I have seen some products the
> > drive across a twisted pair and seem to recover a signal from something
that
> > does look much like a signal.
> > Thanks!
> > Todd
> >
> > Todd DeRego
> > Senior Signal Integrity Engineer
> > Lucent Technologies INS
> > 200 Nickerson Road
> > Marlborough MA 01752
> > (508) 786-2168
> > [email protected]
> > >
> >
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