180 µH at 120 mA — what the ratings mean for your filter or decoupling node
The LQH43MN181J03L is a drum-core wirewound inductor rated 180 µH ±5% at 120 mA continuous. The 4.5 Ohm max DCR means at full rated current the winding dissipates about 65 mW — negligible for most boards, but if you are running near the current limit in a tight thermal spot, the self-heating shifts the inductance a few percent as the ferrite core warms. Unshielded construction means the stray field couples into nearby traces. Keep a keep-out zone around the 1812 footprint if you have a sensitive analog or RF node within a few millimeters.
Frequency range — where this inductor actually works
The self-resonant frequency is 5 MHz. Above that the inductor behaves capacitively, so the useful band for filtering or energy storage tops out around 2–3 MHz. The Q factor is specified at 796 kHz — 40 minimum — which is decent for a drum-core part in this inductance range and tells you the AC losses are manageable up to a few MHz. Test frequency for the 180 µH value is 1 MHz, right in the middle of the useful range. If your switching regulator runs above 3 MHz, this part is not the right choice — look at the LQH43 series' shielded variants or a ferrite-bead alternative.
Board-fit and temperature envelope
1812 (4532 metric) footprint, 4.50 mm × 3.20 mm, seated height 2.80 mm. Standard pick-and-place, no special reflow profile beyond the usual for ferrite-core wirewounds.