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Boost converter, 3W...shielded or unshielded inductor?

cupoftea

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Hi,
In the past, always used shielded inductors for low voltage DCDC’s….but does it really matter?.....can an unshielded inductor be used instead?...they are much much cheaper.
Eg, supposing doing a Boost converter, 60kHz, 3W, 12Vin, 16Vout….using shielded inductor RFS1113-104ME (100uH) or unshielded inductor RLB1314-101 (100uH).

RLB1314-101 (100uH).

RFS1113-104ME (100uH)
https://www.farnell.com/datasheets/2017955.pdf

Is it going to make any difference?
 

scopeprobe

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Functionally you can use shielded or unshielded but unshielded will radiate MORE which can interfere with local circuitry and almost certainly can give compliance issues. I highlight MORE as even shielded will radiate, just less. I always take the view that if you can eliminate EMI at source then do so otherwise you stack up the issues til the end which can be problematic and difficult to solve.
 
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cupoftea

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Thanks very much for your info......also, i think now we can split it into two areas.....
1....Areas involving EMC
2....Areas involving noise which may actually make the circuitry somewhere malfunction.

Would you say that shielded inductors are far more about 1 than 2?

Is it realistic to say that 2 isn't terribly relevant at all?
 

scopeprobe

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Thanks very much for your info......also, i think now we can split it into two areas.....
1....Areas involving EMC
2....Areas involving noise which may actually make the circuitry somewhere malfunction.

Would you say that shielded inductors are far more about 1 than 2?

Is it realistic to say that 2 isn't terribly relevant at all?

Not sure where your going with your thought process there. Inductors are a component like any other, use them incorrectly they can cause problems and use them correctly they can solve problems. In EMC they can be used in filters to limit RF currents as part of a filter to pass emissions but in a switching converter for example they can often be the source of the problem due to large switching currents present in the coils. Shielded inductors are just a way of trying to control stray magnetic fields which can cause both EMC and circuit malfunction depending on its proximity and interaction to a sensitive (susceptible) node. As a designer you always have options, eliminate the susceptible node (possibly redesign), increase proximity between source of issue (more space required), reduce the strength of the field (magnetic screening), screen the susceptable node, ferrite screening, filtering, the list goes on... The down side with screened devices is usually lower saturation currents, larger physical devices, increased weight, increased cost.
 
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