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LM20333: TINA SPICE switcher convergence

FarronDacus
Intellectual 780 points
Part Number: LM20333
Other Parts Discussed in Thread: PSPICE-FOR-TI, TLVM13630

Tool/software:

Hello:  I am trying to perform transient simulation of a switching power supply using the LM20333.  The available model is for TINA SPICE, so that is what I am using. 

However, the basic simulation will not converge.  I have using values off the data sheet for a 12V input being switched down to a 3.3V output.  The sim starts showing no errors such as disconnected nodes or wires.  I have tried many variations of adjusting the transient parameters PIVREL, PIVTOL, and maximum iterations.  I've also tried applying initial conditions and switching between trapezoidal and gear integration.  Nothing affects the transient simulation in the slightest.  It runs out to 38% completion on a 1ms run, and then hangs with failure to converge. 

Can you provide any advice on getting this model to run?  The file I am using is added below. 

Thanks,

Farron

LM20333-1P0.TSC

  • 0
    TI__Guru 50120 points

    Hello Farron,

    I would highly suggest using the newer devices like the TLVM13630 to simplify your design and also use the latest simulate software (PSPICE-FOR-TI) that is currently being supported.

    Are you open to using the newer devices or do you have a specific need to use the LM20333 device? 

    Regards,

    Jimmy

  • 0
    Intellectual 780 points

    Hi Jimmy, thanks for the quick reply.   The LM20333 is already designed in, and we are looking to improve its performance.  Are you saying that the Tina SPICE model provided by TI won't work?  And that because of that, I should try a different switcher that has a PSPICE model that will work?

  • 0 in reply to FarronDacus
    TI__Guru 50120 points

    Hi Farron,

    It should work but because this is an older program that I am not particularly familiar with I'll need to ask around to find someone who can help look into it, as the newer devices are all created on PSPICE-FOR-TI and what I am more familiar with.

    Given that it today is a Friday and most US based engineers here are out of the holiday weekend, I hope to get back to you sometime next week after consulting with someone who is more used to using this program.

    Hope this is okay with you.

    Regards,

    Jimmy

  • 0 in reply to Jimmy Hua
    Intellectual 780 points

    OK Jimmy, thanks, I'll be standing by until next week. 

  • 0 in reply to FarronDacus
    TI__Guru 50120 points

    Thank you for your understanding and patience.

  • 0 in reply to Jimmy Hua
    TI__Guru 50120 points

    Hello,

    Can you please try to use and modify the following TINA file?

    The default file works and when running analysis > transient and model regulates to the default expected 3.3V

    snvm369.tsc

    Regards,

    Jimmy

  • 0 in reply to Jimmy Hua
    Intellectual 780 points

    Hi Jimmy:  OK, your file runs OK and mine does not.  When I go through the differences one by one, it seems to be the optional snubbber diode I was using is the problem.  With the snubbere diode, no transient sim options will let it converge.  Without the snubber, just the standard defaults run fine.  If you don't have any suggestion on getting the sim to run with the snubber, we can consider this closed. 

    Thanks, Farron

  • +1 in reply to FarronDacus
    TI__Guru 50120 points

    Thank you for confirming here.

    As such I will be closing this thread as we were able to resolve the modeling issue.

    Thank you for using the E2E forum.