Subject: [IBIS-Users] How to set the Power Clamp Reference
From: Henrik G. Madsen (hgm@vitesse.com)
Date: Thu Jul 31 2003 - 02:09:42 PDT
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
_____ ________
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| / \
- ---
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| / \
- ---
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|-----|
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-
___| |
| / \
- ---
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----------------- 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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