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

If you really can't build test cards ( ask your management what is worse 
a few $ on test cards or late shipment of product, I know which I would 
choose), then the DDR2 reference DIMM modules do have probing points as 
close to the BGA  pad as they can get. I would follow the same practice 
and simulate with the probing you envisage using, and then correlate 
this with your measured results.

Regards

John



arsenault, brian wrote:

>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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