[SI-LIST] Re: PMC connector with no ground returns

Steve,

Steve,

Every signal will have a ground return path that passes through the 
closest ground pins on the neighboring PMC connectors.  You will 
essentially create a huge open slot between the two boards that will be 
quite unpredictable.  Crosstalk and emissions will go through the roof.

Don't do this.  Bad engineer, bad .... bad!


scott


Steve Mercer wrote:

>SI-List Members,
> 
>I have an application that requires using all 64 available pins on a PMC
>connector for data signals (i.e. no local ground returns). The signals are
>3.3V single-ended data lines with a rise time on the order of 1ns. The data
>will be sampled at 133MHz. The connector in question will be one of a
>grouping of four (in a standard PMC arrangement) and the other three
>connectors have plenty of ground pins.
>My question is this: What nightmares can I expect with regard to crosstalk,
>ground bounce, EMI, and signal integrity in general, and how much will the
>available grounds on the adjacent connectors lessen the undesirable effects?
> 
>Regards,
> 
>Steve Mercer, P.Eng.
>SBS Technologies (Canada), Inc.
>101 Randall Dr.                    Phone (519) 880 8228
>Waterloo ON                       Fax     (519) 880 8118
>N2V 1C5                               smercer@xxxxxxx
> 
>
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-- 
Scott McMorrow
Teraspeed Consulting Group LLC
2926 SE Yamhill St.
Portland, OR 97214
(503) 239-5536
http://www.teraspeed.com




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