Hi, everyone.

I'm trying to simulate a buck converter using BSZ340N08NS3 Infineon Mosfets to evaluate power dissipation of this device. At Infineon webpage¹, I found a .lib designed with many mosfets models including thermal characteristics of the devices and tried to use it, but the simulation got an error like:

"Fatal Error: Analysis: Time step too small; time = 2.38304e-08, timestep = 1.25e-19: trouble with node "n009""

When this kind of error occurs, it usually means the schematics or the models have some kind of problem. I'm not sure I did the importing procedure the right way, but I couldn't find the problem.
I included the ".inc OptiMOS3_80V_LTSpice.lib", placed the "NMOS_thermal5" symbol provided by Infineon and changed the "Spice Model" option with "BSZ340N08NS3" wich is the .SUBCKT name of the model I want to use.

Here is the schematic and the archives of my simularion:


¹->https://www.infineon.com/part/BSZ340N08NS3-G?tab=simmodels

 

Hi, everyone.

I'm trying to simulate a buck converter using BSZ340N08NS3 Infineon Mosfets to evaluate power dissipation of this device. At Infineon webpage¹, I found a .lib designed with many mosfets models including thermal characteristics of the devices and tried to use it, but the simulation got an error like:

"Fatal Error: Analysis: Time step too small; time = 2.38304e-08, timestep = 1.25e-19: trouble with node "n009""

When this kind of error occurs, it usually means the schematics or the models have some kind of problem. I'm not sure I did the importing procedure the right way, but I couldn't find the problem.
I included the ".inc OptiMOS3_80V_LTSpice.lib", placed the "NMOS_thermal5" symbol provided by Infineon and changed the "Spice Model" option with "BSZ340N08NS3" wich is the .SUBCKT name of the model I want to use.

Here is the schematic and the archives of my simularion:
View attachment 362565

¹->https://www.infineon.com/part/BSZ340N08NS3-G?tab=simmodels

Tj is an input and should be connected to voltage source that sets the temperature.
Tamb is an output and is a temperature monitoring pin.

 

Tj is an input and should be connected to voltage source that sets the temperature.
Tamb is an output and is a temperature monitoring pin.

That's not what the library comment says:

*****************************************************************
* thermal nodes of level 3 models: *
* *
* .SUBCKT IPB019N08N3 drain gate source Tj Tcase *
* Tj : potential=temperature (in °C) at junction (typically *
* not connected) *
* Tcase : node where the boundary contition - external heat *
* sinks etc - have to be connected (ideal heat sink *
* can be modeled by using a voltage source stating the *
* ambient temperature in °C between Tcase and ground. *
* *
*****************************************************************

The junction temperature is what we monitor to make sure the device is in the safe operation range. The other pin is actually Tcase, Tamb is just the label net I connected that pin. In that case, my simulation uses an ideal heatsink. Not ideal approach, since the results would be impossible to reach in real life. I could put a resistor with the Rt_ja to get a more conservative result, I believe.