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

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From: Fred Balistreri (fred@apsimtech.com)
Date: Wed Oct 11 2000 - 10:41:21 PDT


Michael Nudelman wrote:
>
> 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
I think what Todd is saying is that the backplane is already designed
or he has no control over the backplane design. Todd check Vitesse
Semiconductor, they may have what you are looking for.

Best Regards,

> > > >
> > > > 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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-- 
Fred Balistreri
fred@apsimtech.com

http://www.apsimtech.com

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