Re: Bidirectional Pad with 5.0V tolerant input

David Makihara wrote:
>
> IBIS Users:
>
> I had created an IBIS model for one of our devices that have 5 volt tolerant
> I/O pads. This specific I/O pad is capable of driving to 3.3V but can
> tolerate input voltages up to 5V. Voltage sweep ranges (ie. table entries)
> are shown in 1) below.
> I had also set "[Voltage Range] 3.300V 2.9700V 3.6300V"
> for this specific pad. However, I'm concerned with using [Voltage Range] for
> this pad and feel as though the "Reference" voltage parameters should be
> used. However, I'm at a loss on how to use these "Reference" parameters
> listed in 2) below.
>
> 1) Are the appropriate voltage sweep ranges appropriate?
> [GND_clamp] -5V -> 5V
> [POWER_clamp] -5V -> 0V
> [Pulldown] -5V -> 10V
> [Pullup] -5V -> 10V
> 2) What values should be applied to the following?
> [Pullup Reference]

3.3v

> [Pulldown Reference]

Ground

> [POWER Clamp Reference]

5v

> [GND Clamp Reference]

Ground

---------------------------------------------

Think of it this way: the pullup current must
track changes in the pullup reference, the power
clamp current must track with the power clamp voltage,
etc. Typically, the V/I curves go to zero current
at 0 volts (the reference potential) and the physical
rail that has the same property is the right one.

-- 
D. C. Sessions
dc.sessions@tempe.vlsi.com