Subject: RE: [IBIS-Users] How to set the Power Clamp Reference
From: Muranyi, Arpad (arpad.muranyi@intel.com)
Date: Thu Jul 31 2003 - 08:38:24 PDT
Henrik,
It seems that your two options end up being the same, since your
VDD values will be 3.3, 3.0 and 3.6 for generating the typ., min.,
and max. IV curves, for which the PWL table yields 2.3, 2.5 and
2.7, respectively. That unusual relationship at VDD = 0 .. 2.86
is not going to happen when the VDD range is 3.0 .. 3.6.
Also, in IBIS you can't use equations or relational tables for
expressing one voltage as a function of another one, so you can
only do your second option as far as the IBIS syntax goes.
Arpad Muranyi
Intel Corporation
================================================================
-----Original Message-----
From: Henrik G. Madsen [mailto:hgm@vitesse.com]
Sent: Thursday, July 31, 2003 2:10 AM
To: ibis-users@eda.org
Subject: [IBIS-Users] How to set the Power Clamp Reference
Hi
I hope that I can get some feedback on this.
I have the below simplified output driver with a pullup and pulldown transistor and some clamp diodes.
VDD = 3.3 V
VDD2 = 2.5 V
VSS = 0 V
VDD VDD2
_____ ________
| |
| / \
- ---
___| |
| / \
- ---
| |
|-----|
| |
-
___| |
| / \
- ---
| |
| |
----------------- VSS
When generating the I-V curves for the IBIS model, the POWER CLAMP and GND CLAMP curves should include the parasitic current running in respectively the Pullup and Pulldown transistor, when they are off as I understand it.
What would be the best solution for controlling the Power Clamp voltage during IBIS model generation?
1) Just using the [Voltage Range] = 3.3V 3.0V 3.6V along with a controlled supply, which control the VDD2. (VDD2 scales with VDD)
E_VDD2 VDD2 VSS PWL(1) VDD VSS 0,0 2.84,2.84 2.86,2.3 3.0,2.3 3.6,2.7
or
2)
Using the
[Pullup reference] = 3.3V 3.0V 3.6V
[Pulldown reference] = 0.0V 0.0V 0.0V
[Power Clamp Reference] = 2.5V 2.3V 2.7V
[GND Clamp Reference] = 0.0V 0.0V 0.0V
I prefer #1 since it ensures that the power and ground clamp voltages are scalled from -3.3V to 6.6V
Any comments?
Regards
/Henrik
_____________________________________
Henrik G Madsen
HW Engineer, M.Sc.E.E
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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