LTSpice Component Lib-Model

[lesabb]

Hello all, just started using LTSpice and it's helping me a lot to understand stuff. I'm building a PSU using a TL783 and trying to measure output and other things. Where can I find LTSpice models for regulators like 78XX, 317, 783, etc...thanks

L   

PS: don't want to put in a voltage source to replace it

[liquibyte]

I'm in the middle of an os change so I can't verify right at this moment but I believe xreg can do the 78XX and 317.  Not sure about the 783 though.  TI has an extensive pspice model collection that I've used quite a bit.

[lesabb]

That's great but not familiar with xreg. Total newbie here. I'll check TI. Thanks

[liquibyte]

Check out http://ltwiki.org/?title=Components_Library_and_Circuits#A_Large_LTspice_Folder_from_Bordodynov as well as the rest of that wiki.  I learned quite a bit from there on how things work.

[lesabb]

Thank you! This is great! How do I edit the xreg to get +24V?

[liquibyte]

You can "edit" the component much like you do a resistor or a cap to enter values.  I think there's a field "xreg" or some such that you can click on (doubleclick?) that will reveal a drop down where you can pick the model of the regulator that you want to use.  As far as getting 24V out of it, that depends on the input and the resistors used on output and adjust.  You can even use a pot as the adjust to gnd resistor and change the value of it from 0 to 1 and model a variable voltage PS.  The fun part comes with learning how to put various loads on the output to model more accurate real world behavior such as ctrl-right click on a component to measure its power.  Just read the various tutorials on the net and play around with it and you'll learn how it all works.

[lesabb]

OK. If I right click it to assign a value like a resistor or something I see a few lines: Prefix, Name, SpiceModel, Value, Value2, etc..But changing those gives me error messages

[liquibyte]

OK, you have to install the http://ltwiki.org/files/LargeCollection.zip to get the xreg I was talking about.  You'll have to install the contents of the lib folder in that archive into the same folder in the LTSpice install folder.  The particular xreg I've been referring to is in the folder [Vreg] (F2, double click [Vreg] it's at the bottom).  Place that in the schematic and right click on it then double click the spice model and you should get a drop down with the different models available.

Sorry it took so long but I had to install wine and then LTSpice and then the library.  I just switched back to Gentoo so wine had to compile first.

[lesabb]

Thanks a bunch! All that worked OK but there is no 7824 or 783 in the list. Any idea what i can do to edit one of the list into a 7824 for example? or where to find a 783.

[liquibyte]

Most spice models aren't all inclusive like that particular one is.  What you'll have to do now is us a generic part and pull in the spice model from the program itself (i.e. using an include directive .include TL071.301.sub).  I don't think the TI spice models include those so you'll have to Google around a bit to see if they've been made by someone else or try making them yourself.  I've not had to learn how to make one yet so you're on your own if you can't find them, or unless someone else here has and is willing to share.  The wiki mentioned above has fair tutorials on how to do includes and such and it's not hard once you get used to it.

[lesabb]

Thanks! I found it with nice directives on how to do it properly. Thanks for the help.

L

[liquibyte]

Glad I could help.  LTSpice is fun and can be really useful, just be aware of its limitations and understand (or at least do) the math behind what you're trying to achieve and things usually work out ok.  Most of the big vendors have pspice models so you can usually find the parts you're trying to work with.  TI has really good ones, Linear parts are generally encrypted so are not as useful for learning, ON has models that are on par with TI's for the most part.  Everyone has their own way of doing things so you'll have to get used to each vendor but I usually just google "part pspice" or "part ltspice" and end up on the page of what I'm looking for.  TI's complete spice model library is here and the ones specifically useful to LTSpice are this one and this one.

[lesabb]

Great, this will surely help!

[Smokey]

I know you said you don't want to put in a voltage source, but... why?  Is there some aspect of a regulator that you think is effecting your circuit?  Do you have some reason to believe that the device models for the regulators accurately model all the physical quirks of the real regulators?  You can always add extra parameters to a voltage source like series resistance and capacitance if that's what you are looking for. 

In my opinion one of the important spice skills is knowing what you can replace with an abstract block so the simulation can focus on the parts of the circuit you actually need to model.  Too much stuff, and it probably won't converge anyway.