LMZ14202EXT: Phase and Gain Margin

Gabriel Santos Pinto

Intellectual 585 points

Part Number: LMZ14202EXT
Other Parts Discussed in Thread: LMZ14202

Good afternoon,

I'd like to know the gain and phase margin for this component, I can't find it in the datasheet.

Can someone help me with this?

Thanks in advance

Gabriel

over 6 years ago

0 JohnTucker over 6 years ago

TI__Guru**** 191445 points

I do not directly support LMZ14202, but I can tell you that the gain and phase margin are application specific. It will depend on your output voltage, output capacitance and Cff value. I am somewhat surprised that the loop response was not provided for the EVM though.

0 Gabriel Santos Pinto over 6 years ago in reply to JohnTucker

Intellectual 585 points

Thanks for the reply in such short notice, I'll look into it.

0 Gabriel Santos Pinto over 6 years ago in reply to JohnTucker

Intellectual 585 points

By the way is there a way to obtain the open loop response data? Can someone provide this in this forum?
Thanks once again.

0 JohnTucker over 6 years ago in reply to Gabriel Santos Pinto

TI__Guru**** 191445 points

I'm not sure what may or may not be available. There is no average model in the tool folder and Webench doe not support any ac analysis for this part. Also, the EVM is not designed to easily check the loop. As this is a "module", it probably depends on which basic IC it is based on. I am assigning this to a person more familiar with power modules.

0 Denislav Petkov over 6 years ago

TI__Mastermind 18940 points

Hello Gabriel,

The control architecture for this part is a "constant on-time" or COT. This architecture is based on hysteretic type control but the switching frequency is almost constant. Getting a conventional frequency response plot from this type of architecture can interfere with the control loop operation and lead to incorrect results.

Another way to measure the loop stability is by load transient (time domain) simulation.
You should be able to do this in WEBENCH with this regulator.

There is also a load transient response plot in the datasheet (see figure 27) and the user guide (see page 7 - the plot is actually for the 3A version. 2A step should be even better).

What are the conditions/design specs you are considering?
We may be able to get a transient response plot for your specific case.

Cheers,
Denislav

0 Gabriel Santos Pinto over 6 years ago in reply to Denislav Petkov

Intellectual 585 points

I think that information will be enough, thank you very much for your help

0 Gabriel Santos Pinto over 6 years ago

Intellectual 585 points

There is another aspect regarding this component that I'd like to ask. (If someone wants to redirect this other question to another thread it's fine by me)

We are using a model of this component in LTSPICE, however its simulation is extremely slow (about 30 minutes!!).
We're in need of performing a Monte-Carlo analysis and hundreds of iterations are needed so this isn't viable... Is there any solution that can allow to speed things up?
Even though I mentioned LTSPICE, if someone has a way of making it faster on TINA I'll happy to follow that tip.

Once again thanks a lot for your help.

Best regards
Gabriel

0 JohnTucker over 6 years ago in reply to Gabriel Santos Pinto

TI__Guru**** 191445 points

I typically see simulations lasting many minutes as well. It is the nature of those simulations. One thing you can do is make the start up (slow start) time faster. I think we have run Monte-Carlo type simulations for other projects in the past. Let me see what method they may use.

0 Gabriel Santos Pinto over 6 years ago in reply to JohnTucker

Intellectual 585 points

Thanks a lot. Please let me know if you find something.
Best regards.

0 Gabriel Santos Pinto over 6 years ago in reply to JohnTucker

Intellectual 585 points

Have you found something regarding the Monte-Carlo simulations?

Also do you know if there's any model for TINA that can be faster?

Sorry to be pressing but I have to present some results to my client soon.

Should I redirect this question to a different thread to make it more visible?

Thank you.

Gabriel Sá Pinto

0 JohnTucker over 6 years ago in reply to Gabriel Santos Pinto

TI__Guru**** 191445 points

I asked a couple people, but did not get a definitive answer. I think you may want to make a separate post in the Simulation Models Forum. Maybe someone there will have a better idea. I typically just accept long simulation times.

0 Gabriel Santos Pinto over 6 years ago in reply to JohnTucker

Intellectual 585 points

I'll do that. Thanks once again for your help.
Best regards.

Power management

Power management forum

LMZ14202EXT: Phase and Gain Margin