4.7 µH shielded wirewound for DC-DC filtering
The Murata LQH3NPN4R7MJRL is a 4.7 µH shielded wirewound inductor in a 1212 (3030 Metric) SMD package. It is part of the LQH3 series and uses a ferrite drum core with a wirewound construction, giving it a self-resonant frequency of 40 MHz. Rated at 710 mA with a saturation current of 1.18 A, this part handles the ripple current in a buck converter's output filter without saturating the core, as long as the peak current stays under the Isat limit.
DCR and current: the thermal budget trade-off
The 144 mOhm maximum DC resistance sets the I²R conduction loss — at 710 mA, the self-heating is roughly 73 mW, which is manageable in the 1212 footprint but should be checked against the board's copper pour area for thermal relief. Shielding with a ferrite core keeps the magnetic field contained, so this inductor can sit next to sensitive analog traces or other magnetics without coupling noise into adjacent circuits. The 40 MHz self-resonant frequency is well above the switching frequency of most DC-DC converters (typically 500 kHz to 2 MHz), so the inductor behaves as a pure inductance in that band — no capacitive crossover until well above the operating range.
Board-fit and temperature envelope
Surface-mount reflow follows standard lead-free profiles. Operating from -40°C to 105°C, the ferrite core material maintains its permeability across the full automotive interior temperature range, though the DCR will increase with temperature per the copper wire's positive temperature coefficient.