Tool/software: TINA-TI or Spice Models
Hi there,
I have a circuit made, but when I try to run AC or DC analysis, "operation point not fount" error pops up. Tried to increase iteration numbers etc, non of them helped.
First i downloaded recommended design, ctrl+c -> ctrl+v , later i downloaded the not encrypted Macro (.LIB) file for the part, and created it in TINA, but same error.
The error is at "D_D11" line, we think the macro is wrong, because we tried to run in on several computers, and even the "LM3481 TINA-TI Load Transient Reference Design (Rev. B)" not working (downloaded from TI).
Any ideas what to change in parameters, or in macro?
Thank you very much!
Have a nice day :)
-Szabi
ps.: the "calculating" field first works with "current source level[%] 100" and when change it to "Shunt conductance[S] 101m", the error happens.
Szabi,
This TSC file is working as expected. It is setup to do Load transient sims on a 12V application and the results are as expected. Can you share the file with me privately: e2e.ti.com/.../3032.08-adding-friends-sending-private-messages
Sazbi,
You will NOT be able to run DC/AC analysis directly on Transient switching regulator model. The spice simulators like TINA-TI cannot find a steady state operating point (by fundamental operation, switching regulator is switching between multiple states and there is no single steady state operating point) and hence cannot perform DC/AC analysis. Some of the switching regulator models also have averaged model available along with the transient model which is used to perform AC/DC analysis. But for the part you are looking at "LM3481-Q1" averaged model is not available.
You may still be able to estimate AC behavior (loop gain and phase) from transient analysis using Fourier series extraction as in the below paper / reference : 
. It is spice simulation / software version of network analyzer. SIMPLIS simulator does this automatically for you - gets the AC response directly from transient switching model.
Regards,
Srikanth Pam | Online Design Tools
