Here's the proof (better than just referencing the manual, I got the simulator to tell me). If you use this netlist:
Code://
model withTnom bsim4 type=n tnom=50
model withoutTnom bsim4 type=n
MwithTnom (d g s 0) withTnom w=1u l=0.5u
MwithoutTnom (d g s 0) withoutTnom w=1u l=0.5u
opts options tnom=34
models info what=models where=screen
This (as you can see) has two models defined, one which explicitly sets tnom to 50, and one which doesn't have it set. Additionally I have the global tnom set in the options statement. Finally I'm using an info analysis to output all the model parameters.
Here's what it produces (irrelevant parameters chopped out for the sake of brevity) using the latest MMSIM71 ISR (what I had handy):
Code:********************************
Model parameter values `models':
********************************
Model: withoutTnom
Primitive: bsim4
type = n
level = 14
...
fcsw = 500e-03
tnom = 34 C
trise = 0 C
ute = -1.5
...
Model: withTnom
Primitive: bsim4
type = n
level = 14
...
fcsw = 500e-03
tnom = 50 C
trise = 0 C
ute = -1.5
...
So that proves what I was saying - the global option only affects models which don't have tnom explicitly set themselves. Hope this helps to convince your CAD group!
Regards,
Andrew.