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

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From: Michael Nudelman (mnudelman@tellium.com)
Date: Wed Oct 11 2000 - 10:23:34 PDT


You are re-designing it anyway! Why not change material? FR-4 has high losses at
2.5Gigs.

What are your trace runs? How long, what impedance?

Todd Derego wrote:

> I don't want to use FR4 but I'm kinda stuck with a backplane I didn't have
> anything to do with and they would like to go faster without changing the
> backplane. I'm not sure this will work but have to make sure it won't before
> I go and design a new backplane. It already has broadside coupling in the
> backplane. I can change the plug in cards as I need to and luckly I see a
> lot of opportunity there, but I don't know it if will be enough or not.
> Thanks!
> Todd
>
> > -----Original Message-----
> > From: Michael Nudelman [SMTP:mnudelman@tellium.com]
> > Sent: Wednesday, October 11, 2000 11:12 AM
> > To: Todd Derego
> > Cc: si-list@silab.eng.sun.com
> > Subject: Re: [SI-LIST] : 2.5Gbps across a backplane?
> >
> > 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
> > > tderego@lucent.com
> > > >
> > >
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