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1. Pspice To Lt Spice
2. Ltspice Transistor Models

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Oct 02, 2013  IBIS Model to SPICE model converter Tool,But can not work. I want to convert from ADuM14001.ibs. Please teach me how to convert. Single switch forward converter topology has been selected for this design. PSpice A/D®, the simulation and analysis tool of OrCAD® products.

I am designing a buck-boost regulator for a course at school and I would like to use the OnSemi ntk3139p PMOS transistor. OnSemi provides a few spice models for this part and I am getting stuck converting the Pspice file so that it is usable in LTspice. I realize I could pick something else, but I wanted to take this opportunity to dive into some of the nitty gritty in spice.

Some of the references I have been following for spice are:

• There are more but I don't have 10 reputation points yet to post them

The Pspice file in question is listed bellow:

My crack at converting it is:

I have rearranged some of the lines so that they resemble some of the other subcircuit LTspice files that I have been looking at with the netlist first and the model definitions second and I have added the parenthesis to the parameters of the model directives. Most of the subcircuit file makes sense to me but a few of the devices I am not sure about such as FI2. I think this is a current dependent current source but it may not be used properly here. I am not sure where I am going wrong here as the error I am getting in LTspice is

The way I implement my NTK3139P.sub is:

• I save the NTK3139P.sub file in C:Program Files (x86)LTCLTCspiceIVlibsub
• Open LTspice
• Create New symbol
  • Pin numbers coorelate with subcircuit definitions
  • In attributes: Prefix = X, Value = ntk3139p
  • Saved where it can be seen by LTSpice
• Restart LTspice
• Create super simple schematic to test it with the FET, a resistor, a voltage source, and ground
• Run a .tran 1 simulation
• The aforementioned error occurs

Any help debugging this and/or explanations of where I went wrong or a friendly point to some more general spice literature would be appreciated!

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1 Answer

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If I simply save that PSpice file to a ntk3139p.lib file and import it in LTspice, it all works fine:

The Rds(on) looks in line with the datasheet for that part.

What you need to keep in mind is to change the PMOS statement line to X (because it's a subcircuit) and match the name to the subckt name declared in that lib. Ctrl-click to access the advanced properties page for the FET:

This is actually explained in detail at http://www.linear.com/solutions/1083

And if you actually want to import that model into LTspice so that you don't have to use an .include statement, what you need to do is

1. Copy the aforementioned ntk3139p.lib into LTspiceIVlibsub; this directory can [and does] contain both .lib and .sub files.
2. Create a ntk3139p.asy in LTspiceIVlibsym (or in one of its subfolders, in which case the component will show up in the corresponing category in the F2 select component dialog). This .asy file is initially a copy of pmos.asy that comes with LTspice in this case. Now you need to edit this ntk3139p.asy file either in a text editor or using LTspice itself (via Edit->Attributes or Ctrl+A) so that it reads:

Now you can add the new component, but since we're using X as type it automatically get labelled as an IC (U) rather than MOSFET as before. But we don't need an .inc line anymore for the simulation to work:

Honestly this procedure is usually not worth the hassle for me... and if you reinstall LTspice or load your schematic on a different machine, you have to do it all over again, never mind that it becomes less clear in the schematic what components you need[ed] extra libraries for. Furthermore, you can no longer change the MOSFET by right-clicking on it an picking a new model. If you try that with your custom asy file, you get:

Which for me is the most annoying part. So I don't recommend doing this import procedure for MOSFETS; I think it's only worth the hassle for ICs.

I honestly don't know exactly what the .sub files are restricted to contain in LTspice, but the ones that come with the program are all binary files containing LT's proprietary models, some of which also make use of LT's extensions like steady and so forth. I don't think the .sub binary format that LTspice uses is publicly documented anywhere.

Pspice To Lt Spice

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• Jim Thompson

posted on
February 12, 2010, 5:41 pm
Anyone know if there's an LTspice to PSpice Schematics converter?
And vice versa?
It seems it should be relatively easy to do... both are text format.
...Jim Thompson
--
James E.Thompson, CTO mens
Analog Innovations, Inc. et

Ltspice Transistor Models

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