LM3421: LM3421 low ripple current

CS kk

Part Number: LM3421

dear

If there have LM3421 low ripple current sulotion such as sch or calculated inductance excel? performace details show as below:

Input above 48V, output 43V, average current 3A, ripple current maximum plus or minus 200mA, thanks in advance

over 3 years ago

0 Tuan Tran74 over 3 years ago

TI__Mastermind 18890 points

Hello,

Section 8.2.1.1 has the design equations for you to calculate your values. Section 8.2.7 give you an example of a Buck regulator for your application if input volte is always above output voltage.

Thanks Tuan

0 CS kk over 3 years ago in reply to Tuan Tran74

Intellectual 400 points

dear

Section 8.2.1.1 and Section 8.2.7 show in the LM3421 datasheet?

0 Caroline Fuschino over 3 years ago in reply to CS kk

TI__Intellectual 1675 points

Hello,

We are looking into this, and an engineer will get back to you by the end of the day with updated sections for these equations.

Thanks,

Caroline

0 Tuan Tran74 over 3 years ago in reply to Caroline Fuschino

TI__Mastermind 18890 points

Hello CS,

Yes, the sections mentioned are in the data sheet.

Thanks Tuan

0 CS kk over 3 years ago in reply to Tuan Tran74

Intellectual 400 points

dear Tuan Tran

I am sorry that I find nothing about Section 8.2.1.1 and Section 8.2.7 show in the LM3421 datasheet，could you help to show？thanks in advance

0 Tuan Tran74 over 3 years ago in reply to CS kk

TI__Mastermind 18890 points

HI CS,

I am sorry, I was looking at an older version of the specification. Please see section 9.2.1.1 where we have the requirements and section 9.2.1.2 (page 35) on down we have the equation for inductor and all the power stage components. Section 9.2.7 shows the schematic along with requirements and part list for a Buck regulator.

Thanks Tuan

0 CS kk over 3 years ago in reply to Tuan Tran74

Intellectual 400 points

dear tuan

9.2.7 For example, in the BUCK scheme, the 700K frequency configuration is RT 35.7k and CT 1NF, and the corresponding formula is Fsw=25/ (RT*CT). However, in the previous formula, Fsw=25*(Vv-VO)/(RT*CT *Vin) is used to introduce the BUCK, which is a little contradictory.

any advise? thanks in advance

0 Tuan Tran74 over 3 years ago in reply to CS kk

TI__Mastermind 18890 points

Hi CS,

The Rt value in the part list for the Buck is not correct and it's a typo error...Please use the formula in section 9.2.1.2.2 for Rt calculation.

Thanks Tuan

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LM3421: LM3421 low ripple current