Subject: RE: [IBIS-Users] Need help with IBIS/ECL question
From: Jeremy Plunkett (jeremy@serverworks.com)
Date: Fri Mar 14 2003 - 18:37:49 PST
John,
I suggest you use a simulator that allows you to set up the supply rails to
the IBIS model yourself, rather than generating the supply connections
internally. This way there is no need to modify your IBIS model.
The only such tool I am aware of is Hspice, but other simulators may allow
this also with some special option. In Hspice, you'll need to set
power=off, connect the pullup and power clamp nodes to your GND rail and the
pulldown and groundclamp nodes to the -5v rail, and connect a 5v voltage
source (and a power delivery model if you have it) with the + node on GND.
The signals that control the IBIS model on the "core" side don't have any
relationship to the IO rails so they will still need to switch from 0-1v.
I haven't tried this myself but as far as I know it should work.
Jeremy
-----Original Message-----
From: owner-ibis-users@server.eda.org
[mailto:owner-ibis-users@server.eda.org]On Behalf Of Beal, Weston
Sent: Friday, March 14, 2003 9:07 AM
To: ibis-users@server.eda.org
Subject: RE: [IBIS-Users] Need help with IBIS/ECL question
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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