3.9 µH drum core wirewound in 1812
The Murata LQH43MN3R9M03L is a 3.9 µH drum core wirewound inductor in the LQH43 series, built on a ferrite core and terminated for surface-mount reflow assembly in the 1812 (4532 Metric) footprint. Rated for 500 mA DC with a maximum DCR of 380 mOhm, the I²R loss at full current is about 95 mW — well within the 85°C ambient ceiling for an unshielded part in free air.
Self-resonant frequency and Q factor
The self-resonant frequency is 41 MHz, meaning the inductor behaves inductively up to that point; above it the parasitic capacitance dominates and the impedance rolls off. Q factor is 20 at 1 MHz, typical for a ferrite-core wirewound in this inductance range — adequate for filtering and DC-DC output stages where the switching frequency sits well below 41 MHz.