[SI-LIST] Re: Unconnected pins in a connector carrying differential signals
- From: "DAmbrosia, John F" <john.dambrosia@xxxxxxxxxxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Fri, 4 Oct 2002 16:10:01 -0400
Jineshwari.B,
Running XAUI signaling has become quite common in backplane applications.
Tyco Electronics has demonstrated XAUI signaling with multiple chip vendors
using its Z-PACK HM-Zd connector.
See any of the following links -
Mindspeed -
http://web1.mindspeed.com/mspd/news_events/news_files/12142001-1.htm
Marvell -
http://www.marvell.com/Internet/News/Show_News_File/1,2410,305,00.html
PMC-Sierra -
http://investor.pmc-sierra.com/ireye/ir_site.zhtml?ticker=pmcs&script=410&la
yout=-6&item_id=275224
Mysticom - http://www.mysticom.com/news/04_15_2002.html
PMC-Sierra -
http://investor.pmc-sierra.com/ireye/ir_site.zhtml?ticker=pmcs&script=410&la
yout=-6&item_id=291767
So I don't think you need to use coaxial cable :)
Now as far as your question goes - you didn't indicate the connector you are
using. Grounding can change the impedance. So you should be careful. If
you are using any of the high-speed connectors similar to the Z-PACK HM-Zd,
extra grounding shouldn't hurt.
John D'Ambrosia
-----Original Message-----
From: Warren Birmingham [mailto:warren@xxxxxxxxxxxxxxx]
Sent: Friday, October 04, 2002 2:31 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Unconnected pins in a connector carrying
differential signals
Greetings.
From experience with 3.1GHz clocks and signals having EMI
ramifications, I recommend that you use coaxial cable with connectors
on each board for this function. It will not only better preserve your
SI issues but keep you out of trouble with a lot of internal noise in
your box that couples into everything. Impedance control is hard
enough at these frequencies, and this will both preserve and protect it.
Warren Birmingham
Epsilon-Mu Consultants
On Friday, Oct 4, 2002, at 10:53 US/Pacific, Jineshwari Baratharajan
wrote:
>
> Hello SI Experts,
>
> We are designing for a very high speed system which
> carries a 3.125Gbps differential signals onto another
> card. The connector which interfaces the two cards has
> lot of free pins.
> Will connecting the free pins to ground do any good in
> terms of crosstalk/SI.
> Or should we leave the pins free.
> Any Suggestions.
>
> Regards,
> Jineshwari.B
>
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