1.2 mH ferrite drum core — what the ratings mean for the BOM
The LQH43MN122J03L is a 1.2 mH unshielded wirewound inductor on a ferrite core in the 1812 (4532 Metric) surface-mount package. The 45 mA current rating is the DC current at which the inductance typically drops by 10% — stay below this for the nominal value to hold. The 30 Ohm max DCR means a 1.35 V drop at full rated current, which matters for low-voltage rails where the inductor's series resistance eats into the supply margin. The self-resonant frequency of 1.8 MHz sets the upper bound for useful filtering — above this the inductor behaves capacitively. The Q factor of 40 at 252 kHz tells you the loss tangent in a tuned filter or resonant tank at that frequency; a higher Q means sharper selectivity and less heating in the core.
Temperature range and storage reality
The ferrite core material's permeability drifts with temperature; the inductance tolerance (±5%) includes this drift across the full range.
Package footprint and board-fit note
The unshielded construction means the magnetic field extends beyond the package — keep sensitive traces or other magnetics at least one body width away to avoid coupling. Standard reflow profile for ferrite-core inductors applies; the component is not moisture-sensitive per typical Murata handling, but store reels in a dry environment below 30°C to prevent oxidation on the termination pads.