07-06-2012 08:19 AM
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
07-06-2012 03:34 PM
07-07-2012 12:44 PM
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.
07-10-2012 09:24 AM
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.
07-10-2012 09:31 AM
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:
Anyway, good luck with your modeling tasks!