The two things that I wish were never invented in SPICE

Discussion created by arpad_muranyi on Oct 13, 2008
Latest reply on Dec 3, 2008 by weston_beal

There are two things in SPICE that I wish were never invented by the

authors of the language:


1)  .global nodename

2)  .option scale = value


These two commands can actually be very useful and convenient

for circuit designers, who tend to work on one buffer at the time,

because they can reduce the amount of typing necessary for writing

netlists and/or models, improving productivity.


However, these commands can cause a lot of problems when two

different designs, having conflicting global nodes and/or scaling

coefficients must be simulated together in the same simulation.

This would usually happen in Signal/Power Integrity (SI/PI) simulations

when the engineer is trying to design a system which obviously

involves more than simulating just one buffer at the time.


In my experience, SPICE models are most often written primarily

for circuit designers, and the SI/PI people are not considered in this

process.  When the design of a buffer is done, the models are just

handed over to the SI/PI engineers, and that's when the problems

usually begin.  To make things worse, by this time circuit designers

are quite often done with the project and are reluctant to go back to

make modifications to the SPICE models on the request of the SI/PI



So my recommendation is to STAY AWAY FROM these two features

of SPICE to save a lot of trouble down the road.