LT3092 model

[david_c_partridge]

Has anyone created a Multisim/Ultiboard part for the Linear Technology LT3092?

[david_c_partridge]

I've hacked up an HB which behaves like the LT3092 datasheet, but will only operate down to 3V rather than 1.2V.  It is based on an opamp and a couple of xistors.

I guess it is possible to convert the HB into a model?  Can you provide guidance please

[_user32]

David,

I think I have a prior post on how to do this. Try searching ni.com on subckt model in multisim.

Basically you rename all the external IC pins in the created HB as needed and strip off any extraneous test circuitry. Then you export the netlist (or just open the netlist viewer) and copy his into a text file. Keep all .models and other subckt statements. I usually flatten all R and C components (take out the .model and the model header line for these simplest types). Resistors should just read: rR1 net1 net2 1000 as an example.

Wrap what's left with a .subckt modelname pin1 pin2 pin3 (etc...) and end it with .ends modelname to enclose the model.

At this point use the component wizard and copy or create a symbol and map into footprint and this model as needed.

Regards,
Pat N

[david_c_partridge]

I think I must have done that wrong, as it didn't work.

I've attached the two files:  "LT3092.ms11" is the HB, "LT3092 Test.ms11" is the test circuit which is currently wired to the component I created.

However when it is wired to the HB in the circuit it works, but as currently wired to the component, it doesn't.

What did I do wrong please, and how do I fix it.

Thanks

Dave

[_user32]

Dave,

It looks like you did everything right and actually the model appears to be working.  I think leaving the HB model disconnected in the circuit is messing up Multisim's ability to accurately model the circuit (it might be making some implied high impedance connections to ground which may be impacting the overall design - I'm not sure).    However, I do know that if you take out the HB model or wire it up in a separate circuit, the SPICE model you created appears to be working correctly - or at least the same way the HB works in a stand alone circuit (please verify).

Here, I have added a potentiometer into the loop so you can interactively change the set resistor to change the current through the load.

Regards,

Pat Noonan

[_user32]

Dave,

Also here is a tutorial that I put together that documents the steps on "Building a SPICE Macro Model from Multisim Schematic".   I use this technique in many cases where I cannot locate a SPICE model but can build an approximate circuit using the datasheet.   I am assuming this is similar to what you did for this LT3092 model.   

This tutorial is located in the "Circuit Design Community" portal of this ni.com site (I recommend joining so you can get notified of updates as new stuff is posted).  Here is the link:

https://decibel.ni.com/content/docs/DOC-16246

Anyway, good luck with your modeling tasks!

Regards,

Pat