LMR16020: Is it possible to reduce the integrated Soft Start in the SPICE model?

Rasmus Kjærsgaard

Part Number: LMR16020

Hi,

I'm currently simulating a SMPS design using LMR16020. I'm trying to do an AC Sweep in order to get a Bode Plot to evaluate the stability of the design.

However, simulations takes quite a while (~10min to simulate 10ms). I would assume the is due to PSpice also running all the UVLO and OVLO features of LMR16020.

I was wondering if it is possible to edit the SPICE model, to reduce the integrated soft start of 4ms, in order to reach steady-state faster and shorten simulation times?

over 6 years ago

0 JohnTucker over 6 years ago

TI__Guru**** 191445 points

Hi User,

That pspice model for LMR16020 is a time domain model. You will not be able to generate a Bode plot from it. For stability analysis, you can look at the output voltage time domain response to a load step change. For a Bode plot you may want to look at your design in the Webench on line design tool. It supports a Bode plot. To answer yur direct question, the SS time is fixed, but you can bypass it by setting SS=1 for steady state solver directly under the IC symbol.

0 Rasmus Kjærsgaard over 6 years ago in reply to JohnTucker

Prodigy 80 points

Hi John,

Thanks for the answer.

I will look into your suggestions.

0 Rasmus Kjærsgaard over 6 years ago in reply to JohnTucker

Prodigy 80 points

Hi John.

I have a little update on my problem.

I've tried to create a Bode Plot 'manually' in PSpice using the method described in this guide from TI: http://www.ti.com/lit/an/snva364a/snva364a.pdf

The reason I'm asking is, that I've made the same test on the actual board, which had a similar crossover-frequency to the one simulated in PSpice. (app. 9.5kHz)

I've also simulated my design in Webench

0 JohnTucker over 6 years ago in reply to Rasmus Kjærsgaard

TI__Guru**** 191445 points

Hi User,

To generate the Bode plot in pspice you would need an average model. You can get an idea of the ac characteristic by examining the time domain response to a step load transient. There is an app note about it, but I will have to search for it.

0 JohnTucker over 6 years ago in reply to JohnTucker

TI__Guru**** 191445 points

User,

The app note is located here:
www.ti.com/.../slva381b.pdf

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LMR16020: Is it possible to reduce the integrated Soft Start in the SPICE model?