Subject: [IBIS-Users] Need help with IBIS/ECL question
From: John Gunser (gunser@lucent.com)
Date: Fri Mar 14 2003 - 04:54:23 PST
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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