RE: [IBIS] BIRD95.3: Power Integrity Analysis using IBIS

Arpad wrote:

1)  Are receiver switching currents important enough for SSO and PDN
simulations to address them in this BIRD?
Mike>>> I honestly don't know enough about receiver currents to say.

2)  What do you suggest we should do when you say: "It's just a shame that
we are still going down that path and not prescribing flexible circuit
models" if not AMS?
Mike>>> Replace the [R Equiv] etc. with something like [Circuit Call],
except allow it to call an [Internal Circuit] as an alternative to calling
an [External Circuit]. This would allow embedding simple passive circuits in
the IBIS file, maybe limiting the language to SPICE, or maybe not. 

Mike

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-----Original Message-----
From: Mike LaBonte [mailto:milabont@cisco.com]
Sent: Wednesday, March 30, 2005 9:34 AM
To: Muranyi, Arpad; 'ibis'
Subject: RE: [IBIS] BIRD95.3: Power Integrity Analysis using IBIS

Actually I was not even thinking of the dynamic current draw when a receiver
switches. That's a good point, but not only is [Composite Current] totally
tied to the presence of output waveforms, IBIS does not have any convention
for triggering the start of any kind of waveform in response to an input
event.

My thought was simply that other buffers in the package and even elsewhere
on the PCB can swing the power voltage that supplies an input buffer; SSO
reaches receivers. Indeed, the simulator may even choose to model the power
source with ripple! The receivers will cause dynamic current flow in
response to any voltage change at the power terminal, even if the voltage
change comes from elsewhere on the PDS.

About Arpad's "sinking feeling" question, I have been involved with the
macromodel approach since 1994. At Cadence I saw how versatile the set of
primitives defined by Kumar is, able to handle all post-2.1 IBIS additions,
complex receivers, pattern equalization, etc., just by translating IBIS
syntax to a simple macromodel template. Most IBIS simulators already have
everything or almost everything needed to do it, and you get a lot of bang
for the buck. As someone with a software background I would love to play
with AMS languages, but having been successful with the macromodel approach
all along I see no need. Also, as far as I know AMS involves a lot of buck$
and would leave all but 2 simulator companies with a big disadvantage.
Sorry, Arpad :)

Mike

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