What the 230 Ω at 100 MHz means for your DC bus
The ACM4520-231-2P-T000: This is a two-line common-mode choke from TDK's ACM series, built for power-line EMI suppression. The 230 Ω impedance at 100 MHz is the common-mode peak — the differential-mode inductance is intentionally low, so the choke attenuates conducted noise riding on the DC rail without saturating from the 3 A DC bias current. The 50 mΩ maximum DCR keeps the I²R loss at 3 A to 0.45 W. In still air that self-heats the ferrite about 8–10 °C, leaving margin at the 85 °C upper operating limit. On a board with any airflow the derating is negligible.
Horizontal 4-pad SMD package, 4.70 x 4.50 mm footprint, 2.00 mm seated height. The pads are on the long edges — the part sits flat, not upright, so reflow paste inspection is straightforward. Standard reflow profile for a ferrite body; no special bake-out required unless the reel has been exposed to humidity beyond the MSL label. The ferrite material's Curie temperature is well above 125 °C, so the impedance holds across the operating band.