[SI-LIST] Re: Question on SI measurement/validation without recei ver access

 Brian,

You've gotten yourself into a tight spot here. I guess your parts are BGAs so 
you can't contact the actual pin, right? The next best thing, but clearly not 
ideal, is to probe at the nearest via and compare that measurement to the 
simulated waveform at that via. If those waveforms compare very well then you 
have good confidence in you simulations and can use the simulation results to 
get waveforms that you would never be able to measure anyway.

Regards,
Weston


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On 
Behalf Of arsenault, brian
Sent: Wednesday, September 29, 2004 8:02 AM
To: 'si-list@xxxxxxxxxxxxx'
Subject: [SI-LIST] Question on SI measurement/validation without receiver access

Folks...

I'm looking for some suggestions and ideas on how to perform SI measurements 
and correlate them to simulations when you don't have access to the receiver 
pin.

For example, one of our designs is looking at back-to-back mounting of DDR-2 
memory chips, and based on the spacing of the board, the vias close to the 
receivers (the RAM's, when a read operation takes place) will not be 
accessible.  The same thing would apply to probing signals at a receiver that 
is using blind and buried vias.

Traditionally, all of our technology has utilized only through-vias, and we 
have been able to probe directly on the pins of the receivers if a via was not 
located very close by.  As we're moving forward, it's apparent that we need to 
find a better way to both show the designer that his/her design will work, and 
for the SI group to correlate their simulations to measurements.

I'm aware that building a test card to validate the buffers is one way to go, 
but in these times, we are trying to minimize extra costs.

Thanks...

Brian


Brian Arsenault
Principal HW Engineer
EMC Corporation
Hopkinton, MA



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