RE: [IBIS-Users] Mixed-Signal Analog IO ?

Lars,

The standard answer to this is that (legacy) IBIS does
not have any provisions to model analog buffers or pins.
If you know enough about what you are trying to model and
if you know the IBIS spec well, you may find some ways to
do it, but this may be a rare situation.  For example, we
made IBIS models for VGA video outputs even though they
are analog signals, with the assumption that for signal
integrity purposes it is enough to model their full
strength to nothing or vice versa transitions, and we
could ignore everything else in-between.

Regarding band gap, I never had to model anything like
that, so I cannot advise you on those...

Arpad
========================================================== 

-----Original Message-----
From: Lars Snith [mailto:lsnith@atmel.com] 
Sent: Tuesday, August 16, 2005 11:51 PM
To: Muranyi, Arpad
Cc: ibis-users@eda.org
Subject: Re: [IBIS-Users] Mixed-Signal Analog IO ?

Hello Arpad,

Sorry for my vague description. I will try to do better below.
It is clear that every buffer type have clamp tables, and that I can 
model analog IO using *-AMS langauges and External Circuit declarations. 
But since my tools fall back on s2ibis2 which conforms to IBIS v2.1 
specification which (correct me if I'm wrong), does not include these 
features, it would be an additional manual procedure to add it.
Hence my question how you did model analog IO (like for example the 
output of a bandgap reference with sink & source capability) in "the 
good old days" with only I,O,I/O,VDD,GND and NA to choose from.
If this is not possible/advisable I will of course have to take measures.

As I hope is clear from the above, I have no intention to add clamps tp 
power pins (although ESD protection calls for snapbacks), that would not 
be a good idea having multiple supplies.


Best regards,  Lars Snith

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