[SI-LIST] Re: Question on SI measurement/validation without receiver access
- From: HaroldLSJ@xxxxxxx
- To: arsenault_brian@xxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Wed, 29 Sep 2004 13:01:09 EDT
Brian,
First, measure the active (powered) input impedance of your receiver over a
frequency sweep at least ten times higher than your range of interest. Next,
synthesize a network equal to this impedance sweep. Now build a small
daughter board the same size as your receiver component with at least 5
adjacent
traces terminated with the synthesized network. Depending on the size of the
network you may have to realize it in thin film and/or chip and wire
technology. This daughter board technique will allow you to directly measure
the SI
characteristics of the incoming signal and compare it to your simulations.
The daughter board can be fitted with BGA style balls on the bottom side at a
number of places such as IC Interconnect in Colorado.
Harold L. Snyder, Jr.
Scientist & Consultant
Begin Included Message dated 9/29/2004 10:06:17 AM Central Daylight Time,
arsenault_brian@xxxxxxx writes:
===============================
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
===============================
End Included Message.
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