Impedance and current ceiling
The BLM15AX121SN1D delivers 120 Ohms of impedance at 100 MHz — the frequency where most conducted EMI from switching regulators and digital clocks lands. The 700 mA current rating means it handles the supply rail of a BLE SoC or a sensor node without saturating the ferrite.
DC resistance and thermal budget
DC resistance maxes at 130 mOhm. At 700 mA the I²R loss is 64 mW — negligible for a 0402 part, but in a dense layout with multiple beads sharing a trace, the cumulative heating can shift the impedance curve.