33 µH drum-core selection for DC-DC filtering and bias-T circuits
The Murata LQH32MN330K23L is a 33 µH drum-core wirewound inductor in the LQH32 series, unshielded, with a ferrite core. The 115 mA DC current rating is the point at which the inductance typically drops by 10% due to core saturation — above this, the effective inductance falls off and ripple current increases in a buck converter output filter. The 3.5 Ohm maximum DCR produces an I²R loss of about 46 mW at rated current — negligible in a power rail but significant in a low-impedance bias-T where the DC bias current flows through the same winding. The 12 MHz self-resonant frequency means this inductor stays inductive up to about 6-8 MHz in practice; above that, the parasitic capacitance dominates and the impedance rolls off.
Unshielded construction and layout considerations
Because the LQH32MN330K23L is unshielded, the magnetic field radiates from the drum core. In a dense PCB layout, keep a clearance of at least one component width (3.2 mm) from sensitive analog traces or other inductors to avoid mutual coupling. The 1210 (3225 metric) footprint is standard and fits the common LQH32 pad layout used across the series. The ferrite core material maintains its permeability across this range with a typical drift of less than 5% from 25°C to 85°C.
Active production and ordering posture
The base product number LQH32MN covers the full inductance range in this unshielded drum-core family. The -330K suffix encodes the 33 µH value and ±10% tolerance. Tape-and-reel packaging is standard for the 1210 footprint, compatible with automated pick-and-place assembly.