Drum Core Chokes1 min read
Bay note 11 — Drum core when an open path is correct
Open magnetic path, cheap mounting, real EMI cost — when a drum-core choke is the honest answer for a power rail.
Drum cores are unapologetic: the field leaves the part. That is acceptable on many power rails and unacceptable next to a sensitive analog island.
Use a drum when
- Cost and vertical footprint win
- The board has keep-out or a shield can
- Soft saturation from a gapped ferrite is enough
Avoid a drum when
- An ADC, RF front-end or cable sits in the H-field
- You need matched differential behaviour (prefer a toroid CM choke)
Spec strip
State L, Isat, DCR, height and the keep-out you can give it. We will not "make it quieter" without changing geometry — that is physics, not varnish.
Drum core chokes in the catalogue are a starting grid; custom AL is routine.