FreeLists / si-list / [SI-LIST] Re: 2.5Gbit connectors and cables

["Fabrizio" <fzanella@xxxxxxxxx>]

These are all good comments.  It's important to reduce the impact of
capacitive discontinuities.  So reduce the number of vias in the path, add a
clearance for the planes directly under any ferrites or other discrete
components.  Also use a differential ground clearance for the backplane
connector pins, especially on the backplane - the backplane via stubs have a
large effect at 2.5Gbs and above.
And definitely simulate and build prototypes to determine your best options
before your final board designs.
Regards, Fabrizio Zanella
----- Original Message -----
From: "john lipsius" <johnlipsius@xxxxxxxxx>
To: <jtreeve@xxxxxxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
Sent: Tuesday, October 01, 2002 4:57 PM
Subject: [SI-LIST] Re: 2.5Gbit connectors and cables


>
> Jeff,
>
> Assuming coax interconnect....
>
> 1. If the board pairs are 100ohm Zdiff pairs, then interconnecting with
>     coax will present a pretty large problem in that you'll have two
zeven/
>     zodd discontinuities, plus the coax connector stubs in the pcb.
>
> 2. Instead, I would route the board traces as microstrip single-ended on
>     the opposite surface from the the smb mounting surface, or use SMT
>     coax connectors, to mitigate the stub.  Further, I would use 0402
series
>     R to attenuate the signal and slow the edges, also to mitigate the
>     discontinuities.
>     You can always put in a 0 ohm value if needed, but driver amplitude
>     control is better than this approach, if available.  Also, experiment
>     with disabling any pre-emphasis in the driver since the link is short
and
>     discontinuous.
>
> None of the above replaces the need to simulate or prototype.
>
> -John
>
>
> ----- Original Message -----
> From: "Jeff Reeve" <jtreeve@xxxxxxxxxxxxxxx>
> To: <si-list@xxxxxxxxxxxxx>
> Sent: Monday, September 30, 2002 9:43 PM
> Subject: [SI-LIST] 2.5Gbit connectors and cables
>
>
> >
> > SI-List,
> >
> > I need to specify a connector and cable to accomodate board to board
> > interconnect of four 2.5Gbps differential pairs. The length of the cable
> > would be about 2" between boards and the trace on each PCB to the SerDes
> > would be <3" for a total length of 8". Any suggestions, solutions or
> > pointers would be greatly appreciated.
> >
> > Thanks in advance
> > Jeff
> >
> > ------------------------------------------------------------------
> > To unsubscribe from si-list:
> > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
> >
> > or to administer your membership from a web page, go to:
> > http://www.freelists.org/webpage/si-list
> >
> > For help:
> > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> >
> > List archives are viewable at:
> > http://www.freelists.org/archives/si-list
> > or at our remote archives:
> > http://groups.yahoo.com/group/si-list/messages
> > Old (prior to June 6, 2001) list archives are viewable at:
> >   http://www.qsl.net/wb6tpu
> >
>
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
> or to administer your membership from a web page, go to:
> http://www.freelists.org/webpage/si-list
>
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
> List archives are viewable at:
> http://www.freelists.org/archives/si-list
> or at our remote archives:
> http://groups.yahoo.com/group/si-list/messages
> Old (prior to June 6, 2001) list archives are viewable at:
>   http://www.qsl.net/wb6tpu
>
>

------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages 
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu