Board-fit and integration note
The BLM15AG221SH1D: The 0402 footprint keeps the series impedance path short — the bead sits directly in the supply or signal trace without eating board real estate on a dense automotive or portable PCB.
Impedance, current, and DCR — what limits the fit
At 100 MHz the bead presents 220 Ohms of impedance — this is the attenuation peak for conducted EMI in the VHF band, where most switching-regulator harmonics and digital clock edges radiate. The 300 mA continuous current rating sets the DC bias ceiling; above that the ferrite core saturates and the impedance collapses.
Temperature grade and automotive qualification
The AEC-Q200 qualification (passive-component stress test) covers thermal shock, solder heat resistance, vibration, and humidity bias — the bead is screened for the reliability profile an engine-bay or cabin ECU demands. No derating is needed across the band; the impedance curve shifts slightly with temperature but the 220 Ohm peak stays within spec.