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Inductors in series/parallel to lower resistance

ACharnley

Member
I have a buck application where I'm restricted to an inductor with a max height of 1.2mm, I'm using one of the 2.2uH values in the attached image.

Screenshot_2019-12-02_22-40-23.png

I've managed to squeeze the PCB space to fit in another identical inductor, so have the option to parallel or series a second item.

Two 4.7uH in parallel results in 2.35uH, close enough, but according to the max resistance it's going to be nearly the same as the 2.2uH. Similarly if I series 2 x 1.0uH then max resistance is slightly more than the 2.2uH. In other words there seems to be no benefit?
 

ACharnley

Member
But anyhow, how come there's no benefit?

Two resistors would lower the ohms, carry more current
Two capacitors would double the capacity or increase the voltage rating
Inductors - seems to make no difference?
 

kubeek

Well-Known Member
Most Helpful Member
How thick is the pcb? You could theoretically make a cutout and embed the inductor partially in the pcb.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
But anyhow, how come there's no benefit?

Two resistors would lower the ohms, carry more current
Two capacitors would double the capacity or increase the voltage rating
Inductors - seems to make no difference?
Quite simple - in order to get more inductance in a smaller space you have to use thinner wire - so you can get the same result using thicker wire in a larger space.
 

ACharnley

Member
Yes, but then the resistance should be lower? (this is my objective).

The performance with the inductor I'm using is fine it's just read an article which said there's roughly a 1% efficiency increase going from 100mOhm to a 50mOhm inductor for the TI chip I'm using.
 

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