220 µH wirewound in 1812 — what the ratings mean for your filter or DC-DC stage
The LQH43CN221K03L is a 220 µH unshielded drum-core wirewound inductor from Murata's LQH43 series, housed in the 1812 (4532 Metric) surface-mount package. Its 110 mA current rating and 4 Ω max DCR set the conduction loss and saturation floor for the DC bias it can handle in a power rail or signal filter. The 4.5 MHz self-resonant frequency (SRF) means the inductor behaves inductively up to that point; above it, parasitic capacitance dominates and the impedance rolls off. For a buck converter switching at 500 kHz or a low-pass filter below 2 MHz, this part stays well within its inductive region. Unshielded construction means the magnetic field radiates into the surrounding board area — keep sensitive analog traces or other magnetics at least one package width away to avoid coupling. The ferrite core material handles the 220 µH value with a ±10% tolerance, tested at 1 MHz.