Inductance, current, and DC resistance — the three numbers that decide fit
The LQH43MN681K03L: The 680 µH inductance is the primary filter or energy-storage value for the LC tank or DC-DC converter — the ±10% tolerance means the actual value can vary by 68 µH, so the resonant frequency or ripple current calculation must include the worst-case spread. Rated for 65 mA DC, the 17 Ohm max DCR drops 1.1 V and dissipates 72 mW at full current — check the self-heating against the 85°C upper operating limit; a 1812 body on a standard FR4 board with minimal copper area may need derating above 65°C ambient.
Frequency response and Q factor — where the inductor behaves like an inductor
Self-resonant frequency is 2.5 MHz — above this the component behaves capacitively, so the 680 µH value is only usable for switching frequencies or filter cutoffs well below 2.5 MHz, typically under 500 kHz to stay in the inductive region. Q factor of 40 at 796 kHz means the inductive reactance is 40 times the effective series resistance at that frequency — good for tuned circuits where insertion loss matters, but the Q drops off as frequency moves away from the test point.
Unshielded construction — layout implications
Unshielded drum core means the magnetic field radiates from the open side — keep sensitive analog traces, low-level signal lines, and high-impedance nodes at least 5 mm away in the XY plane, and avoid routing a ground plane directly under the inductor that could act as a shorted turn.