Subject: RE: [IBIS-Users] Need help with IBIS/ECL question
From: Beal, Weston (weston_beal@mentorg.com)
Date: Fri Mar 14 2003 - 09:07:22 PST
John,
I don't recall anything in the IBIS specification that prohibits this method, but the more important issue is whether or not your simulator will interpret it as you desire. I kind of doubt that this will work in any of the simulators that I'm familiar with.
If I were in your position, I would just try one simple model and try a simulation in my favorite simulator. You'll need to remove any rising and falling waveforms for the first test, as they surely will cause confusion. If you find that the first test works and you want to add the waveforms back in, then you'll have to find a method to adjust the voltage values to line up with your new model.
Good Luck,
Weston
-----Original Message-----
From: John Gunser [mailto:gunser@lucent.com]
Sent: Friday, March 14, 2003 4:54 AM
To: ibis-users@server.eda.org
Subject: [IBIS-Users] Need help with IBIS/ECL question
Hi All,
I have a few questions I was hoping someone here could help me out with.
Background: I am attempting to perform signal integrity on a 10-15 year old
circuit pack that uses the 100K series of ECL devices. This pack is being
redesigned to replace some DA components and we need to verify the quality of
the other signals. On this circuit pack, these ECL devices interface to
standard 74F, ABT and HC devices that are connected and operating "under water"
(with VCC tied to ground and GRD connected to -5 volts) I have obtained ibis
models for the 74F, ABT and HC parts but now need to modify them to correctly
reflect how they are being used in the circuit.
Questions: Can I simply change the pull up, pull down, ground clamp and power
clamp reference values to reflect the -5V to 0 operation rather than 0 to +5V?
For Vinl, am I correct in assuming it should change to .8V more than -5 or -4.2
volts? Similarly Vinh would be -5 + 2 = -3?? In the output model where Vmeas and
Vref are specified (currently 1.5V and 0v), If I change the Vref to -5V, is the
Vmeas specified to be relative to the Vref (1.5V more than Vref) or is Vmeas
absolute and need to be specified as -3.5V? Any help in sorting this out will be
greatly appreciated! Thanks in advance!
Best Regards
John Gunser
gunser@lucent.com
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