Inductors in series/parallel to lower resistance

A

ACharnley

Member

• Dec 2, 2019

• #1

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.



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?

 

crutschow

Well-Known Member

Most Helpful Member

• Dec 2, 2019

• #2

ACharnley said:

In other words there seems to be no benefit?

Click to expand...

Why would you think there would be?

 

A

ACharnley

Member

• Dec 2, 2019

• #3

Because it's using double the area!

 

P

Pommie

Well-Known Member

Most Helpful Member

• Dec 2, 2019

• #4

Can you source a larger one that does give a benefit and still fits?

Mike.

 

ronsimpson

Well-Known Member

Most Helpful Member

• Dec 2, 2019

• #5

1.2mm is hard. I found 1.7mm at coilcraft.com
2.2uH 1.7mm

 

ronsimpson

Well-Known Member

Most Helpful Member

• Dec 2, 2019

• #6

MGV05122R2M-10, **broken link removed**
CMLS051B-2R2MS, HMLQ32251B-2R2MS, Delta Electronics/Cyntec
IHLP2020ABER2R2M01, Vishay Dale
HMLQ32251B-2R2MS, Delta Electronics/Cyntec
SPM5012T-2R2M-LR, VLS3012CX-2R2M-1, TFM322512ALMA2R2MTAA , TDK Corporation
FDSD0512-H-K2R2M=P3, DFE322512F-2R2M=P2, Murata Electronics
MDMK4040T2R2MM , NRS6014T2R2NMGG,NRS5014T2R2NMGGV, Taiyo Yuden

Hope this helps. Ron S.

 

ronsimpson

Well-Known Member

Most Helpful Member

• Dec 2, 2019

• #7

 

A

ACharnley

Member

• Dec 3, 2019

• #8

Nope, 1.2mm is absolute max (1.0mm is better).

I'm limited length wise as well to about 4mm (and 8-9mm width hence can fit two).

 

A

ACharnley

Member

• Dec 3, 2019

• #9

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?

 

K

kubeek

Well-Known Member

Most Helpful Member

• Dec 3, 2019

• #10

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

• Dec 3, 2019

• #11

ACharnley said:

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?

Click to expand...

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.

 

A

ACharnley

Member

• Dec 3, 2019

• #12

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.