Hello everyone.

I know that there are tutorials around the internet showing that there's no difference between importing an LTSpice third-party model from a PSpice model. Sadly after trying to follow them I keep on getting error messages unknown circuit node.

I suppose it'd be best if I'd describe what exactly, step by step, I'm doing:

1. I downloaded a PSpice model for LM5085 from an official TI website.
2. The model came as a ZIP file but even though there were other files inside of it, I've exctracted only the "LM5085_TRANS.lib"
3. I've moved the "LM5085_TRANS.lib" file from my desktop to "...\AppData\Local\Programs\ADI\LTspice\lib\sym" folder
4. I've booted up the LTSpice and opened the "LM5085_TRANS.lib" file
5. I've right-clicked on the blueish label that started with ".SUBCKT" and selected "Create symbol"
6. LTSpice asked for a confirmation and I've given it.
7. An autogenerated model poped up in front of me. A "LM5085_TRANS.asy" file. I navigated to "File" and pressed "save"
8. Created a new schematic and using the component search function I've placed the model. I tried to run the simulation without adding any external circuitry but I was prompted: "U1:e_abm100: Unknown circuit node: "nc_05" requested in behavioral source"

How can I solve this issue?
Any help would be appreciated.

Also I'm pinning the ".lib" file to this thread.

 

Your problem is probably that you do not have all the pins connected. I copied a reference design from the TI datasheet, but the simulation won't run and it throws a :timestep too small error." These errors are notoriously difficult to track down, but some people are very good at it.

 

You likely need to connect the model file nodes to the correct nodes on the symbol file.
You right click on each of the symbol pins while editing the symbol ( which gives the window below), and then add the proper netlist Label and order for the pin.
For example (below) the Netlist Order for the INP node of this arbitrary model is 2.


------------------------------------------------------------
The symbol Netlist Order is in sequence from left to right in the .SUBCKT line of the model file.
Thus below, the Netlist Order is 1 for IADJ, 2 for RON, 3 for FB, 4 for GND, etc.

Make sense?

Note that you may get a simulation error if you try to simulate the IC with no external connections.

 

You likely need to connect the model file nodes to the correct nodes on the symbol file.
You right click on each of the symbol pins while editing the symbol ( which gives the window below), and then add the proper netlist Label and order for the pin.
For example (below) the Netlist Order for the INP node of this arbitrary model is 2.

View attachment 294608
------------------------------------------------------------
The symbol Netlist Order is in sequence from left to right in the .SUBCKT line of the model file.
Thus below, the Netlist Order is 1 for IADJ, 2 for RON, 3 for FB, 4 for GND, etc.

Make sense?

Note that you may get a simulation error if you try to simulate the IC with no external connections.

View attachment 294607

Nonsense! When you autogenerate a symbol from a subcircuit it takes care of that for you. At least on LTspice XVII it took care of it for me when I did it. Could it be that LTspiceIV doesn't do that for you??

You can clearly see the simulation ran for a few picoseconds of simulation time before throwing a timestep too small error. I did try all combinations of integration method and solver to no avail. I even tried it on Version 17.1.8

 

Hi,
Interesting online note.
E
https://e2e.ti.com/support/tools/si...orum/448435/about-lm5085-pspice-model-problem

 

Hi,
Interesting online note.
E
https://e2e.ti.com/support/tools/si...orum/448435/about-lm5085-pspice-model-problem

You're suggesting I should use TINA-TI instead of LT Spice?

 

You're suggesting I should use TINA-TI instead of LT Spice?

Hi K,
Looking through the reports online, it appears only Tina can make it work, and TI are not advising how to correct the problem for LTSpice.

E
Clip:
t looks like you may be getting a convergence error. Unfortunately, we are unable to support LTSpice. Please consider using TINA-TI. The LM5085 model is already available in TINA-TI so you should have a good working starting point. Also, you can look into the Export of this spice model from WEBENCH to TINA-TI directly. The advantage is that you not only get the spice model and schematic setup for you, but WEBENCH will provide you with a workign schematic as well. You can also use other features within WEBENCH to fine tune and optimize your design as well.

 

I see that the e_abm100 doesnt have the = sign before Value, like others do. Maybe try adding that?

 

I see that the e_abm100 doesnt have the = sign before Value, like others do. Maybe try adding that?

@kubeek nice to see you again. There were multiple instances of the missing = sign. Inserting them at the appropriate locations has no effect. This is not really surprising since there are other places in LTspice where there they can be there or not.

I have to say that TI's response is a giant middle finger, but from the corporate perspective it is to be expected. Still not a good look when you are trying to promote the sale of a product. Would I get the same response to another problem I might have? Do you really want to do business with these people? Makes you wonder.