Subject: 3v5 tolerant IO's for IBIS model generation

From: Elias Lozano <[email-masked]>
Date: Fri, 25 Sep 1998 17:10:08 -0700

Hi,

I would like to find out if any one has an example of a 5V tolerant 3.3v
volt IO IBIS model generation. It seems to me that the IBIS model is not as
straight forward when mixed voltages are used in the IO and not having
direct pull-down/pull-up diodes.

Any information or examples would be really helpful.

Thanks a lot

Elias

---

From: "Muranyi, Arpad" <[email-masked]>
Date: Mon, 28 Sep 1998 07:59:00 -0700

Elias,

We made many 5 volt tolerant 3.3 volt models.  It is really not that
difficult 
to make them.  You can use the pullup reference voltage keyword at 3.3 V and
the
power clamp reference voltage keyword for the 5 V calmps.  Sweep the device
5 
volt relative when it is 3-stated, and sweep it 3.3 relative when it is
driving 
high.  This is to reflect which rail the pullup and the clamp is connected
to, 
but you actually don't even have to do this if you don't care about how the 
currents flow through the package.  In that case, you can sweep everything
3.3 
relative, but don't be surprised that in the 3-state mode your clamps will
show 
up 1.7 volts shifted compared with the way they normally look like.

Arpad Muranyi
Intel Corporation
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Hi,

Thanks a lot

Elias