LMR36006: ferrite bead v/s inductor

DARSHAN M M V

Part Number: LMR36006

Hello team,

I always had a confusion with the Inductor and ferrite bead in the power input line ( buck converter) and output line.

Please can you tell me when we have to use the ferrite bead over the inductor , what are advantages of using ferrite bead over the inductor.

Please provide the document which explains my problem if it is avaialble

10 months ago

0 Ben C 10 months ago

TI__Mastermind 47325 points

Hi Darshan,

A ferrite bead is used to reduce noise in a circuit while an inductor (used in a buck converter) stores energy as a magnetic field when current flows through it.

Below is a link that describes more about when and how to use a ferrite bead.

https://www.ti.com/lit/ab/sluaai2/sluaai2.pdf

Ben

0 Ben C 10 months ago in reply to Ben C

TI__Mastermind 47325 points

Hi Darshan,

If there are no further questions, please go ahead and close the thread by clicking on "resolved". Thanks,

Ben

0 DARSHAN M M V 10 months ago in reply to Ben C

Intellectual 265 points

Hello ben ,

Thanks for providing the solution,

I have question w.r.t filter ,

when designing input filter for buck converter , what is the cutt off frequency I have to consider for calculation.

Let say my buck converter is switching at 440KHZ and what is ferrite valute I need to consider.

when selecting a ferrite bead what should be SRF of ferrite bead ( how much difference from operation frequency to SRF)

0 Ben C 10 months ago in reply to DARSHAN M M V

TI__Mastermind 47325 points

Hi Darshan,

I usually start with a decade from the converter's switching frequency for the corner frequency.

Ben

0 Ben C 9 months ago in reply to Ben C

TI__Mastermind 47325 points

Hi Darshan,

Are there any other questions regarding the EMI input filter? If not, please close the thread by clicking on "resolved". Thank you,

Ben

0 DARSHAN M M V 9 months ago in reply to Ben C

Intellectual 265 points

Hello Ben ,

Please can you share me calculation or document you would prefer to design in PI EMI filter

0 Ben C 9 months ago in reply to DARSHAN M M V

TI__Mastermind 47325 points

Hi Darshan,

Below is a calculator to help you design your input EMI filter and an application note for your reference.

6114.Worksheet in Designing Low-EMI Power Converters for Automotive Systems.xls

https://www.ti.com/lit/an/snva489c/snva489c.pdf

Ben

0 DARSHAN M M V 9 months ago in reply to Ben C

Intellectual 265 points

Hello Ben,

if we are using a buck converter IC example LMR36006 , do we have a control over Cin.If not what exactly the Cin stands for and how do we get to know the value

0 Ben C 9 months ago in reply to DARSHAN M M V

TI__Mastermind 47325 points

Hi Darshan,

Yes, you have control over CIN.

Ben

0 DARSHAN M M V 9 months ago in reply to Ben C

Intellectual 265 points

Hello ben ,

Thank for the confirmation , I have few confusion w.r.t Cf Cd and Cin , referring to below diagram

Can please tell me , which capacitor can be considered as Cf , Cd and Cin. your detailed explanation would help us to pass the EMC test which we are planning to conduct next week.

0 Ben C 9 months ago in reply to DARSHAN M M V

TI__Mastermind 47325 points

Hi Darshan,

C1 = Cf

L = Lf

C2 = Cd

CIN = 4.7uF + 2 X 220nF

Ben

0 Ben C 9 months ago in reply to Ben C

TI__Mastermind 47325 points

Hi Darshan,

If there are no further questions, please close the thread by clicking on "resolved". Thanks!

Ben

0 DARSHAN M M V 9 months ago in reply to Ben C

Intellectual 265 points

Hello Ben ,

I have few questions about Pi filter referring to above diagram,

What is the backward cutt of frequency in pi filter and why we need to show importance.

+1 Ben C 9 months ago in reply to DARSHAN M M V

TI__Mastermind 47325 points

Hi Darshan,

I apologize but I have not heard that term before. Can you provide me some info?

Ben

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LMR36006: ferrite bead v/s inductor