I'm working on a power supply simulation and I can't find an LM317 spice model. I've searched and found the code for what I think is the spice model, but I couldn't get it to work correctly. I am using MultiSim 8, and SwitcherCad III. The model for either or both would be awesome or instructions on how to import the spice code into a component on either would be awesome.
I'm working on a power supply simulation and I can't find an LM317 spice model. I've searched and found the code for what I think is the spice model, but I couldn't get it to work correctly. I am using MultiSim 8, and SwitcherCad III. The model for either or both would be awesome or instructions on how to import the spice code into a component on either would be awesome.
Thanks for the model. I cut and pasted it into Multisim, and I got no errors when I ran the program...however my circuit didn't work correctly (no voltage at output). I probably assigned the pins to the wrong locations. Is their a good tutorial for importing spice code into multisim somewhere? I did some searches and just got ewb's site talking about how great multisim is.
I would also like to understand the spice code itself, any good site you reccomend for a brief overview of that?
You might like to try changing the saturation current for QNL and QNP models from IS=1E-22 to IS=6E-13. You will then get the correct reference voltage of 1.25V.
Although this model is supposed to be for the LM317K (TO3 version) you will find that its limiting current is about 0.7 amps with the netlist given, rather than the 1.5A expected, therefore it is closer to the LM317H, E or MDT versions.
You will also have to add a reversed biased 1N4001 across the Adj to output pins to get the correct hard limiting behaviour.
simon.harpham@ieee.org
You might like to try changing the saturation current for QNL and QNP models from IS=1E-22 to IS=6E-13. You will then get the correct reference voltage of 1.25V.
Although this model is supposed to be for the LM317K (TO3 version) you will find that its limiting current is about 0.7 amps with the netlist given, rather than the 1.5A expected, therefore it is closer to the LM317H, E or MDT versions.
..................
I believe you're just trying to emphasize one of the limitations of a Spice simulation. Since there's no way to put the thermal impedance of a device and its heatsink into Spice it obviously can't simulate the thermal current limit of the device. But LTspice certainly can calculate and display the power dissipation of the device so you can design the heatsink accordingly. It can even calculate the average power for an input voltage with significant ripple.
simon.harpham@ieee.org You might like to try changing the saturation current for QNL and QNP models from IS=1E-22 to IS=6E-13. You will then get the correct reference voltage of 1.25V.
Although this model is supposed to be for the LM317K (TO3 version) you will find that its limiting current is about 0.7 amps with the netlist given, rather than the 1.5A expected, therefore it is closer to the LM317H, E or MDT versions.
You will also have to add a reversed biased 1N4001 across the Adj to output pins to get the correct hard limiting behaviour.
Why are you trying to simulate an LM317 IC? It either regulates very well if everything is correct or does not. The Sim program does not know if everything is correct but the LM317 datasheet should show you any problems you might have have.
I have seriously overloaded little transistors (way too much current and heat) in a simulation and LTspice did not notice anything wrong.
Why would you not?
I simulate the LM317 so I know that I have the right component values and it's likely to work in the real circuit without building the circuit first.
I also occasionally use it in ways that a simple voltage source can't emulate.