2.4 mH wirewound — filtering and bias-current limits
The Murata LQH43NZ242K03L is a 2.4 mH wirewound inductor in the LQH3 series, built on a ferrite core and housed in an 1812 (4532 Metric) surface-mount package. The 25 mA current rating is the DC bias at which the inductance typically drops by 10 % — push beyond that and the effective inductance falls off, so the filter corner shifts. With a 53 Ohm maximum DCR, the copper loss at rated current is about 33 mW, which is within the self-heating budget for the 105 °C upper operating limit.
Q factor and self-resonant frequency — where it still works as an inductor
The Q factor is 40 at 252 kHz, meaning the inductive reactance is 40 times the effective series resistance at that frequency — good efficiency for resonant tank circuits or EMI filter traps tuned near that band. The self-resonant frequency is 1.2 MHz; above that the parasitic winding capacitance dominates and the part behaves capacitively. For a low-pass filter, keep the cutoff well below 1.2 MHz to stay in the inductive region.
Unshielded construction — board layout consideration
This is an unshielded inductor, so the magnetic field radiates from the core. Keep sensitive analog traces or high-impedance nodes at least two part-widths away to avoid coupled noise.