Re: Pullup/down data

> (1) When running simulations on an "input buffer with Bus-Hold" to extract clamp
> data, should the bus-hold circuitry be disconnected ?. In other words,
> should we include the contribution from the Bus-Hold circuit in the clamp data.
> I would think not, any suggestions ?

"Bus-hold" circuits typically use two weak inverters connected in a
positive feedback loop. Modeling this with any V/I simulator will be
problematic, because the static V/I curves depend on past history, not
just on present voltage. It is impossible to do this with a V/I
simulator. (Not to mention the implication of negative resistance,
which even some SPICE-like simulators have trouble dealing with.)

In principle you should include everything. You would have to pick one
of the states, for the region where the two V/I curves don't overlap.
If the contribution to current is small, you might justify omitting it;
but then your simulations could be in error if the feature is used.

Regards,
Andy Ingraham
Received on Tue Nov 14 06:13:12 1995