[IBIS-Users] DDR4 simulations using IBIS models

For relatively low bandwidth signals (say < 1GHz) IBIS .pkg style RLC
package models are an adequate solution. As we move into the realm of
DDR4 where the bitrate is say 4 GB/s and the risetime is on the order of
70psec I am wondering what sort of package models IBIS users tend to use
these days.

A 70psec ristime equates to a knee frequency of about 5.7 GHz. For good
signal fidelity the package model should be accurate up to at least 3
times that frequency (and preferably 5 times).

Looking at the options available it is looking like s-parameter models
may be the only variety that is up to the task. The problem with those
from a user's perspective is that the simulation speed is quite slow
compared to RLC based models. From the model makers perspective, it is
impractical to do a "full package" s-parameter extraction to provide
separate models for each net in large packages. It also appears that in
IBIS 5.0 there is no good method to automatically include the proper
s-parameter model (as one can do in current tools by just selecting the
proper pin name or netname to pull in the correct RLC parasitic).

If IBIS BIRD 125 is adopted allowing IBIS-ISS available for package
modeling it seems that will provide a mechanism for the inclusion of
s-parameter package models.

Until the enhancements described in BIRD125 become reality what is
current solution most users are adopting?

Ray Anderson

Xilinx Inc.

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