FreeLists / si-list / [SI-LIST] How many Ground pins are enough

[Ravinder.Ajmani@xxxxxxxx]

Hi Experts,
I had posted the following earlier, when the server was limping back to 
normalacy.  Perhaps, that is why I did not receive a single response. 
Hence I am posting it again.
I am working on a JTAG/Trace interface for our new design.  The current 
design has the following interface between our target card and JTAG/Trace 
Analyzer:

Card -> Pogo pins -> Flex cable with ground plane -> Mictor Connector of 
Trace Analyzer

In the current design, I have used one Ground pin for every high-speed 
signal pin on pogo pin interface (a total of 20 signal  pins and 10 ground 

pins).  However, the new design requires 16-bit data interface (the 
current design has 8-bit interface), and I may be able to increase the 
number of pogo pins only slightly. 

The card can't have any permanent connector for this interface, yet we 
need the flexibility to connect Trace Analyzer at any time.  Hence, pogo 
pins work best for us.

My question is: how many ground return pins will I need for 18 high-speed 
signals between the flex cable and the card, which will assure good signal 

integrity.  The interface runs at a maximum speed of 200 MHz.  Is there 
any way I can simulate this using IBIS simulators.

I will very much appreciate any suggestions. 

Regards, Ravinder
Server PCB and Flex Development
Hitachi Global Storage Technologies
Voice :  (408) 256-7956       Fax :  (408) 256-0550

Email: Ravinder.Ajmani@xxxxxxxx



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