[SI-LIST] : Modeling power noise

Christian S. Rode (csrode@mediaone.net)
Fri, 19 Mar 1999 12:38:01 -0500

Hello, all.

I'm trying to build a pedagogical model of a single line driver, signal
line, termination
and its power environment. I'm building it as an ideal voltage source
with a finite
source resistance with symmetrical drive. I'm looking to highlight
packaging / bypass
issues, not the driver technology.

I'm interested in soliciting feedback on the workability of the model,
usable as an online
simulation (but currently documentation-free) at:

http://www.circuitsim.com/netsim/si/decoupling/

A couple of the values are intentionally provocative, such as the value
for the
inductance from the bypass cap to the ideal source, but I'm looking for
feedback on
the reality of the rest of the rat's nest of inductors.

Modeling the "rest of the world" in terms of a distant ideal source,
other bypass
capacitors, plane inductance / capacitance is what I'd most like
feedback on.

I'm also not sure where "power-supply resonance" would fit here - it
would seem to be
well below 100 MHz. I see instead a resonance between the output
self-capacitance
and the power supply inductance(s).

An uneducated question: does anyone ever extend separate core / IO
power and
(especially) ground off-chip? I'm thinking a second, quiet, ground
reference plane
could be useful. Or is this another reason to go differential?

This is about a couple day's work so there are LOTS of bugs, including
non-convergence
and a peculiar spiking problem that happens to quiescent signals.

Thanks in advance for your comments / suggestions.

Chris Rode
RCI
decoupling@circuitsim.com

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