1.2 mH drum core wirewound — what the ratings mean for the BOM
The Murata LQH43NN122J03L is a drum core, wirewound inductor in the LQH43 series, rated 1.2 mH ±5% at 1 kHz test frequency. The 45 mA DC current rating is the bias current at which inductance typically drops by 10% — stay below this to avoid saturation in a filter or DC-DC output choke. Maximum DC resistance is 30 Ohm, which at 45 mA produces a 61.5 mW I²R loss — negligible in most circuits but worth checking if the inductor sits in a high-ambient enclosure where self-heating compounds the temperature rise. Self-resonant frequency is 1.8 MHz; above that the parasitic capacitance dominates and the part stops behaving as an inductor. The Q factor of 40 at 252 kHz gives a figure of merit for tuned or resonant applications — a higher Q means lower circulating losses at that frequency.
Package and temperature grade — board-fit and environment
The ferrite core is unshielded, so adjacent traces carrying high-frequency or high-current signals may couple magnetically — keep a keep-out zone or orient the inductor orthogonal to nearby magnetics. The ferrite core material has a Curie temperature well above 105°C, so the inductance drop over temperature is dominated by the DC bias, not the thermal profile.
Product status is Active per Murata's lifecycle records — no end-of-life or last-time-buy notice on file.