Re: IBIS at >400MHz

Paul:

You raise some very good points and questions. I don't
have definitive answers. I support using Spice simulation
and measurement as part of the design methodology along
with IBIS based behavioral simulation. I would expect
that as specific IBIS format limitations are identified
with respect to higher frequency simulation accuracy,
proposals to ammend the IBIS format will be made.

Eric Blomberg in "IBIS "models" come of age" in the October 1997
issue of Printed Circuit Design. p. 20 provides a very concise
paragraph that addresses your points and provides some thoughts.
Eric's paragraph follows:

  "Can I use IBIS models for my 600 MHz bus?" The simplest
  answer is yes - if the IBIS provider has validated the
  model at 600 MHz. It is true that the device effects which
  are simplified out of the IBIS model format start to become
  visible about 300 MHz. It is also true that other effects,
  such as dielectric loss, and the modeling engine's way of
  handling this become significant as well. Device package
  models play a larger role. The expectation answer is that
  above 300 MHz, validation becomes a part-by-part issue for
  the entire modeling system.

Bob Ross
Interconnectix

> From: Paul Gregory <pgregory@hpbs2933.boi.hp.com>
> Message-Id: <9710031834.AA20168@hpbs2933.boi.hp.com>
> Subject: IBIS at >400MHz
> To: ibis-users@eda.org
> Date: Fri, 3 Oct 97 12:34:01 MDT

> In future designs, we plan to use interfaces that
> reach beyond 400 MHz. As I think about the tools
> that we need to help us successfully design at that
> speed, simulation is going to be a big part of it.
> But I am concerned that IBIS descriptions and
> simulation techniques may not be adequate to accurately
> simulate at that speed. Perhaps SPICE simulation
> will be required.

> Should IBIS based simulators be capable of accurate
> simulation at speed of 400MHz to 1000MHz?

> When device parasitics play a larger part of the
> equation, is IBIS sufficiently robust to accurately
> describe these parasitics?

> What are the key factors to consider when simulating
> at these higher frequencies?

> What are your thoughts?

> -- Paul Gregory

> phone: (208) 396-5086 USmail: Hewlett-Packard
> fax: (208) 396-4122 M/S 143
> email: paul_gregory@hp.com 11311 Chinden Blvd.
> Boise, ID 83714

 
Received on Thu Oct 9 12:17:24 1997