The LQH43NN271J03L is a drum-core wirewound inductor from Murata's LQH43 series, in the standard 1812 (4532 Metric) SMD footprint. Its 270 µH inductance and 100 mA current rating place it in the mid-value filtering range for DC-DC converter output stages or signal-line chokes where the load current stays under 100 mA.
DCR and Q — the efficiency trade-off
DC resistance is 6.8 Ω maximum — at the full 100 mA rating, the I²R loss is 68 mW, which heats the part above ambient. The Q factor is 40 at 796 kHz, meaning the inductive reactance is 40 times the effective series resistance at that frequency; efficiency is best near the test frequency and drops as you move away from it. Self-resonant frequency is 4 MHz — above that point the inductor's parasitic capacitance dominates and the impedance becomes capacitive. Keep the switching frequency or the noise frequency of interest well below 4 MHz to stay in the inductive region.
Unshielded construction — layout matters
The part is unshielded, so the magnetic field radiates from the drum core. In a dense PCB layout, keep the inductor away from sensitive analog traces, low-level signal paths, or other magnetics to avoid coupling. If crosstalk is a concern, a shielded ferrite-bead or shielded inductor from the same series is a better fit. Operating temperature range is -40°C to +105°C, which covers most industrial and automotive cabin environments. The ferrite core material maintains inductance stability across that band, though the DCR increases with temperature.