What this 4.7 µH wirewound inductor does on the board
The LQH43NN4R7K03L is a drum-core, wirewound inductor from Murata's LQH43 series, built on a ferrite core and unshielded. Its 4.7 µH inductance at 1 MHz test frequency and 500 mA current rating suit it for DC-DC converter input/output filtering, power-line smoothing, and low-frequency noise suppression in surface-mount designs. The unshielded construction means the magnetic field is not contained within a ferrite shield — adjacent traces or components within a few millimeters may couple noise, so layout spacing and orientation matter more than with a shielded part.
Q factor and self-resonant frequency — filter bandwidth limits
With a Q of 30 at 1 MHz and a self-resonant frequency of 38 MHz, this inductor behaves as a pure inductance up to roughly 10 MHz; above that, parasitic capacitance between windings begins to dominate, and the impedance peak near 38 MHz marks the upper frequency limit for effective filtering. For a buck converter switching at 500 kHz to 2 MHz, the inductor's impedance remains inductive with low AC losses, but for a 10 MHz switching regulator the margin to self-resonance is only about 4×, which may introduce ringing or efficiency degradation.
Murata lists the LQH43NN4R7K03L as Active on its lifecycle status — no PCN or last-time-buy notice has been issued. This inductor is suitable for both new product introductions and ongoing production without obsolescence-driven redesign. The 1812 (4532 Metric) footprint and tape-and-reel packaging (cut tape available) keep it compatible with standard pick-and-place assembly.