Subject: [IBIS-Users] s2ibis2 problem with 3-stateable OD drivers
From: Henrik G. Madsen (hgm@vitesse.com)
Date: Tue Nov 26 2002 - 01:24:29 PST
To me it seems that s2ibis2 do not support generation of open-drain models with tri-state outputs properly.
I'm using the Windows version, but I believe that the issue is of general nature.
********** From .s2i file
[Pin]
pad pad pad osoc2_od
-> D EN
D D D input
EN EN EN enable
VDD VDD VDD POWER
VSS VSS VSS GND
[Model] osoc2_od
[Model type] Open_sink
[Polarity] Non-Inverting
[Enable] Active-low
*************
The above will not generate the correct VI tables.
By using the above info, s2ibis2 will generate spice simulations for
1) 'Pulldown curve'
2) 'Pulldown curve with output disabled'
but no 'Ground clamp' simulation.
I assume it then creates the IBIS PULLDOWN curve by subtraction the second curve from the first one (only for negative voltages).
The resulting IBIS model only has one VI curve, the modified PULLDOWN where the clamping has been subtracted. But it does not add the missing current by adding a 'Ground Clamp' curve.
It seems that a correct result only can be obtained by removing the enable signal and run s2ibis2 with that, Or create the missing 'Ground Clamp' curve manually.
Can it be true that s2ibis2 do not support OD-drivers with enable signal?
_____________________________________
Henrik G Madsen
Sr. HW Engineer
Vitesse Semiconductor Corporation A/S
Ethernet Products Division
Hoerkaer 16, DK-2730 Herlev, DENMARK
Direct: +45 4485 5920
Phone: +45 4485 5900, Fax: +45 4485 5901
mail: hgm@vitesse.com
web: http://www.vitesse.com
_____________________________________
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