WEBENCH® Tools/LP2992: LP2992

Selvedin Hodzic

Part Number: LP2992

Tool/software: WEBENCH® Design Tools

Hello together,

I have a question about dimensioning of capacities at LP2992. My switching regulator has the switching frequency of 330KHz and ripple noise of 30mVp-p. I have put this values into the configuration parameters of WEBENCH but it do not adjust accordingly the capacitors. Can I select the following values for my application as shown in the drawing below: Cin=1uF, Cbyp=10nF and Cout=10uF instead of Cout=4.7uF ?

Kind Regards

Selvedin Hodzic

over 3 years ago

0 Stephen Ziel over 3 years ago

TI__Mastermind 29150 points

Hi Selvedin,

Those values will be fine. Actually, I like your Cout better than 4.7uF because using 10uF gives much more margin to the stability specification.

Please be sure to maintain an ESR specification in your Cout of 5 miliohms or greater, to meet the datasheet requirements for stability.

Thanks,

- Stephen

0 Selvedin Hodzic over 3 years ago in reply to Stephen Ziel

Prodigy 210 points

Hi Stephen,

Thank you for your reply!

I have read the following in the forum: " Just put a 0603 or 0805 resistor of 20mOhm...100mOhm in series to the output cap. This will imitate the needed ESR of cap". Must I do the same?

Regards

Selvedin Hodzic

0 Stephen Ziel over 3 years ago in reply to Selvedin Hodzic

TI__Mastermind 29150 points

Hi Selvedin,

That is one option if the ceramic capacitor ESR is too low.
If you go this route I would choose 10mOhm to give you the lowest impedance for transient response while still meeting the datasheet recommendation.

Another option is to use a low ESR dry tantalum capacitor.

Thanks,

- Stephen

0 Selvedin Hodzic over 3 years ago in reply to Stephen Ziel

Prodigy 210 points

Hi Stephen,

If you could just confirm that for me: I understand that if I use a ceramic capacitor whose ESR is less than 5mOhm then everything is fine ? Or as you said dry tantalum capacitor.

Regards

Selvedin Hodzic

0 Selvedin Hodzic over 3 years ago in reply to Selvedin Hodzic

Prodigy 210 points

Hi Stephen;

My mistake. I get it now!

Thank you very much for your explanation!

Regards

Selvedin

Power management

Power management forum

WEBENCH® Tools/LP2992: LP2992