Cross function and Monte Carlo analysis

[evilella]

Dear all,


I am trying to run the Monte Carlo analysis of the offset voltage of a comparator.

For this, I am using the 'cross' function from Cadence calculator. The expression I use is the following one:

cross(VDC("/OUT_SF") 0.9 0 "either" t "time"),

where OUT_SF is the output of my comparator and 0.9 is my threshold value. Before running the Monte Carlo analysis, I do a simple dc simulation with Spectre. However, the simulation fails giving an 'eval err' without further information. To my surprise, if I try to represent with the calculator:

cross(value(getData("/OUT_SF" ?result "dc") "d" 10) 0.9 0 "either" t "time")

which is the same expression as before, but selecting the waveform from the visualization window instead of selecting the net in the schematic, it works! I can see the value of the input voltage when the output crosses the threshold.

Does anybody know why this happens? Can anybody help me to run the Monte Carlo analysis of the cross function, please?


Many thanks,

Eva

 

[pancho_hideboo]

You have to know data sets in psf directory correctly.
And you have to specify data set name.

Don't rely on Caluculator functions in ADE.
These are no more than high level function in OCEAN(=Skill).

You can never utilize full ability of post processing, if you rely on only Calculator functions.

"getData()" is more primitive function than "vdc()".

Show me data set lists in psf directory.

 

[evilella]

Dear pancho_hideboo,


Actually, I have solved the problem using a different approach. For this simulation, the 'cross' function needs to be with VS (source sweep voltage) instead of with VDC. The expression that I simulate is:

cross(VS("/OUT_SF") 0.9 0 "either" t "time")

and all works nicely.


Thank you very much for your reply anyway.

Eva