FreeLists / si-list / [SI-LIST] Re: PMC connector with no ground returns

[Mike Brown <bmgman@xxxxxxxxxx>]

Steve,

Can you say "Save money at any cost."?  I knew you could.

You are about to experience what the Boss in "Cool Hand Luke" was 
talking when he said "We have a failute to communicate."  Your boards 
will have a like failure.

In a word, DON'T.  If you try this, you will die of old age before you 
ever get it to play reliably.

To quote Mr Morrow: "Don't do this.  Bad engineer, bad .... bad!"

Figure out some way to MUX the data lines and do a DDR (both edges of 
clock, not the JEDEC standard) protocol across the backplane.  That will 
free up a large number of pins in the connector.  Or get a connector 
that's about 50% bigger (2:1 signal/ground ratio).  Simulate before you 
build.

Mike

Scott McMorrow wrote:

> 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
>>
>>
>>------------------------------------------------------------------
>>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 technical documents are available at:
>>               http://www.si-list.org
>>
>>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 technical documents are available at:
                http://www.si-list.org

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