Subject: RE: [IBIS-Users] Question about warning message
From: Ingraham, Andrew (Andrew.Ingraham@hp.com)
Date: Mon Nov 18 2002 - 04:56:32 PST
The warning about "extreme currents" probably means that you started
with inaccurate SPICE models.
The clamp diodes might be modeled (in SPICE) with unrealistically small,
or zero, series resistances, causing huge simulated currents at large
voltages beyond the supply rails.
Is it a problem? Yes and no. Most simulations shouldn't stray far into
these regions, and if they do, the huge currents generally steer things
back away from them. But it might mean that the simulated results do
not correctly show what happens in response to normal overshoot
transients.
The best way to fix it, is to correct the SPICE model, and start over.
Or measure how the device actually behaves and modify one or both models
accordingly.
Regards,
Andy
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