LMR38020: Phase margin for LMR38020FSDDAR

miyata.fumiki

Prodigy 100 points

Part Number: LMR38020

Hi team.

We are studying the improvement of the phase margin for LMR38020FSDDAR.

This IC(LMR38020FSDDAR) does not have a terminal for adjusting the phase margin such as the COMP terminal.

Is there any way to improve the performance without additional Cff?

Please refer attached for detail.

20230705_phase margin for LMR38020FSDDAR.xlsx

over 2 years ago

0 Gui He over 2 years ago

TI__Mastermind 28146 points

Hi Miyata

Yes since the COMP is integrated, the most common way to improve the loop performance is by adjusting the Cff.

Have you tried adjusting the Cout ?

Thanks and best regards.

0 miyata.fumiki over 2 years ago in reply to Gui He

Prodigy 100 points

Hi Gui san

Good day.

Thank you for your strong support.

The phase margin was improved by adding the Cout !

+1 Gui He over 2 years ago in reply to miyata.fumiki

TI__Mastermind 28146 points

Hi Miyata

You're welcome. Can you kindly help closing this thread by clicking the 'resolved' button if no other questions?

Thanks and best regards.

0 Ted Casper over 2 years ago in reply to Gui He

Prodigy 90 points

Is there an equation for estimating Cff on the LMR380x0 parts? I cannot find one for the LMR380x0 data sheets. For instance, the LMR336x0 data sheet includes an equation for estimating the maximum value for Cff. Thank you.

0 Gui He over 2 years ago in reply to Ted Casper

TI__Mastermind 28146 points

Hi Ted

There is no equation for Cff in LMR380X0 datasheet. You can refer to this apps note for the Cff design:

https://www.ti.com/lit/an/slva289b/slva289b.pdf?ts=1689828458650&ref_url=https%253A%252F%252Fwww.ti.com%252Flit%252Fds%252Fsymlink%252Flmr33630.pdf%253Fts%253D1689825197544%2526ref_url%253Dhttps%25253A%25252F%25252Fwww.ti.com%25252Fsitesearch%25252Fen-us%25252Fdocs%25252Funiversalsearch.tsp%25253FlangPref%25253Den-US%252526searchTerm%25253DLMR33630%252526nr%25253D497

Thanks

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LMR38020: Phase margin for LMR38020FSDDAR