Subject: Re: [IBIS-Users] Validating IBIS Inputs
From: Ingraham, Andrew (a.ingraham@ieee.org)
Date: Tue May 13 2003 - 10:32:46 PDT
A well behaved driver with output impedance comparable to the transmission
line's Zo, won't generate much if any overshoot.
Try using a rail-to-rail voltage source and about a 10 ohm thevenin
equivalent resistance, driving a 50 ohm transmission line to the receiver.
It is a better signal source for exercising inputs. The delay of the
transmission line sets the overshoot pulsewidth.
Regards,
Andy
> I'm curious as to how other people validate an IBIS input buffer with a
> ground clamp and power clamp curve to the original
> SPICE netlist. If I run a simulation of a driver and receiver with a
> transmission line, and then a driver with a transmission
> line and a lumped capacitor load, I get almost the same result. (Assuming
> a properly made IBIS file) The power and ground clamp
> curves only turn on below Reference Ground or above supply voltage. So if
> I have an input going into my input buffer that has overshoot
> then should I see my powerclamp curve turn on? What types of tests do
> people do to validate that the clamps are behaving as expected?
> (And feel free to inform me on what the expected behavior of the clamps
> should be)
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