Re: inductor polarity

On 2025-02-28 04:50, john larkin wrote:

I need to put 16 of these on a very dense PC board.
 https://www.digikey.com/en/products/detail/murata-power-solutions-inc/19R476C/5798223
 Each of the eight channels needs two of these. If I can put each pair
of inductors close together and with the same current but opposed
field direction, I'll get minimum mag field leakage to other channels
(and to other boards.)
 I see that one lead is longer than the other. I wonder if that implies
a consistent winding direction, so my manufacturing people could use
that as the "pin1" indicator.
 If that's not dependable, I'll have to set up a rig to determine mag
field polarity, and mark one side with a red dot or something.
 I'd rather use surface-mount shielded inductors, but these tall
unshielded drum cores have way more L and less R than a shielded part,
for a given PCB footprint.
 

It works fine, but the total inductance will be somewhat higher than just 2x.
The external field is way less, I use that trick in a sensitive environment (ADC's etc).
If you mount them parallel to the PCB, try alternating 90 degree positioning from pair to pair to minimize coupling.
Arie