Re: non-monotonicity

Jon Powell wrote:

> 3) The device is really non-monotonic in the operating range. If this is
> true, this implies the device is using some active feedback technique.
> If THIS is true then there is some implied delay in the feedback loop.
> This feedback delay is not modeled by IBIS. The IBIS committee has
> requested IC vendors to come forward with SPICE circuit examples of
> devices that exhibit this effect so that we can figure out a behavioral
> mechanism to describe it but (at least to my current knowledge) no such
> circuit has been delivered. So your choices are: Ignore the
> non-monotonicity (that is, remove it from the IV curve) or simulate with
> the non-montonicity but with no info about the delay. Depending on how
> the circuit works, either of these could the best approach and I believe
> different EDA vendors have made different decisions on what is most
> appropriate in their simulators.

Missed the request, Jon. Here's one:

.SUBCKT od_drvr i pad vdd vss
R1 pad rpad 200
MN1 pad ngate vss vss NCH L=0.5u W=200u
MN2 ngate rpad vss vss NCH L=1.0u W=6u
MN3 rpad vss vss vss NCH L=0.5u W=40u
MN4 ngate i vss vss NCH L=0.4u W=50u
MP4 ngate i vdd vdd PCH L=0.4u W=120u
.ENDS od_drvr

Use just about any 0.35u process models. You'll find that the
V/I curve becomes nonmonotonic at higher voltages.

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