Selection of Ferrite Bead

[tiwari.sachin]

I am using a ferrite for 3V3 supply. The one that supplies analog section another to a digital section (External Board)



How should I select the value for ferrite

 

[Mattylad]

1) look at what you can get, suppliers sites - costings etc.
2) read the datasheets

 

[marce]

You have a value on your schematic...
But to select a ferrite, you need to know what frequency of noise you want to attenuate and select a ferrite that has its highest resistance at that frequency.

 

[meetpdp]

Can you your noise frequency range.

 

[tiwari.sachin]

The MCU that I use can run upto 48MHz and I dint find any ferrite that can provide max frequencey at this frequency.

The closest I could find was this

https://www.mouser.in/Search/Produc...virtualkey64800000virtualkey81-BLM18AG221SH1D


Should I be looking for frequency used by the MCU


or the frequency of DC to DC that generates 3.3V. The DC to DC has 570KHz fixed switching frequency

 

[marce]

Harmonics, without specific measurements its hard to guess...

 

[meetpdp]

I think your selection is fine.

Please have a note with DC to DC datasheet also. They have provided some recommendations on C-L-C or L-C values.

 

[FvM]

The rated current specification of ferrite beads might cause misunderstandings. It's a thermal rating, don't expect much choke impedance at this current, the inductor will be mostly saturated.