Active production, automotive-qualified common-mode choke
The TDK ACM2012-900-2P-T001 is an active-production common-mode filter from the ACM series, carrying AEC-Q200 qualification — the automotive passive-component stress test that covers temperature cycling, vibration, and solder-heat resistance. With a 90 Ω impedance at 100 MHz, a 400 mA current rating, and a 190 mΩ maximum DCR, this 2-line filter is sized for signal-line EMI suppression on CAN, LIN, or low-speed data buses where the common-mode noise sits in the 100 MHz band.
What the 90 Ω rating means for the BOM
The 90 Ω impedance at 100 MHz is the common-mode attenuation spec — it tells you how much the filter chokes the noise current on both lines simultaneously. For a 12 V automotive bus switching at a few MHz, the 100 MHz band is where conducted emissions from the switching regulator harmonics land; this filter knocks them down before they radiate off the harness.
The 4-pad configuration is the common-mode choke topology — the two signal lines share the same ferrite core, so the filter suppresses noise on both lines simultaneously, unlike a 2-pad ferrite bead that only filters one line. AEC-Q200 Grade 1 qualification means it passed the 1000-hour high-temperature operating life test at 105°C.