Re: Question regarding the [POWER_clamp] curve

Prasad:

To add to Mike LaBonte's response, it is permissible
to extend both [Gnd Clamp] and [Power Clamp] tables over
the full -vdd to 2*Vdd range. For internal terminators,
this would be a good idea.

If you have ideal 50 ohm resistors to Gnd and also to
Vdd, the [Gnd Clamp] and [Power Clamp] tables might
look like this for Vdd = 3.3 V:

[Gnd Clamp]
-3.3 -66ma -66ma -66ma
0 0 0 0
6.6 132ma 132ma 132ma

[Power Clamp]
-3.3 66ma 66ma 66ma
0 0 0 0
6.6 -132ma -132ma -132ma

For your active devices, you would need to find a
method to extract the actual (transistor) table
information and to properly decompose the extracted
information into the two tables.

A presentation that proposes improvements to
s2ibis2 for internal termination situations was
given under:

  http://www.eda.org/pub/ibis/summits/oct99/nasef.zip

Bob Ross
Mentor Graphics

> Prasad Rau wrote:
>
> Hi,
>
> I am modelling onchip termination for certain IO standards and unfortunately
> the [POWER_clamp] curve
> puts out information from -VDD to 0v. The region of interest( termination
> effects) is 0v to +VDD. Is there a way to input information
>
> ( without modifying the source code of the simulator ) such that the IBIS file
> spits out -VDD to +VDD in the
> [POWER_clamp] curve. By the way, the termination is modelled as a split
> termination ie 50 Ohms to VDD and
> 50 Ohms to GND. These are not passive devices but active( transistors)
> devices.
>
> Thanks in advance,
>
> Regards,
>
> Prasad Rau
> Xilinx
>
>
 
Received on Wed Jul 11 15:55:11 2001