LMR12020: Re: Inductor Selection from datasheet formula and webench calculation doubt

Rajeshmani G

Prodigy 40 points

Part Number: LMR12020

Dear Team,

I am using LMR12020 in my design with below mentioned conditions,

As per datasheet I calculated the inductor value as 38uH

Same way I provided the web bench input as above conditions for circuit,

But I am getting the inductor value as 3.3uH only.

Which one is correct and which inductor value I should implement in my design.

Kindly reply ASAP.

Regards,

Rajesh

11 months ago

0 Yuchang Zhang 11 months ago

TI__Mastermind 18510 points

Rajesh, Commonly it is recommended to use full current ability of converter to choose the inductor rather than the real application current. so recommend to follow Webench data.

Yuchang

0 Rajeshmani G 11 months ago in reply to Yuchang Zhang

Prodigy 40 points

YUchang, As u suggested If I use 3.3uH in my design means my ripple ration will be 4.7 instead of (0.3 to 0.4),

If I use 38uH means my ripple ration will be 0.39.

Kindly clarify ASAP.

Regards,

Rajesh

0 Zixu Wang 11 months ago in reply to Rajeshmani G

TI__Expert 8100 points

Hi Rajeshmani,

My colleague will give you reply next Monday!

BRs

Zixu

0 Yuchang Zhang 11 months ago in reply to Rajeshmani G

TI__Mastermind 18510 points

Rajesh, As I mentioned, the inductor selection and the ripple current ratio should be based on current ability of LMR12020, which means 2A rather than your application current 0.104A.

Yuchang

0 Rajeshmani G 11 months ago in reply to Yuchang Zhang

Prodigy 40 points

Yuchang, As I know that inductor selection is based ripple current ratio should be based on current ability,Kindly clarify when I am providing 0.104A max in web bench why It s calculating for Max current 2A and also I am enterign ripple ratio as 40% it shows same 3.3uH in datasheet calculation I am getting 38uH.

Kindly suggest me is it ok to proceed with 38uH from datasheet calculation or 3.3uH from web bench?

Is web bench circuit is correct or not?

0 Yuchang Zhang 11 months ago in reply to Rajeshmani G

TI__Mastermind 18510 points

The current ability I mentioned is max current 2A of LMR12020, 3.3uH makes sense, when the converter design and validation, it is based on the 2A max current ability.

Yuchang

0 Yuchang Zhang 11 months ago in reply to Yuchang Zhang

TI__Mastermind 18510 points

BTW, the inductor current ability also need to cover OCP value of LMR12020, to prevent inductor saturate during OC happen.

Yuchang

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LMR12020: Re: Inductor Selection from datasheet formula and webench calculation doubt