What this common mode filter does on the board
The TDK ACT45B-101-2P-TL003 is a 2-line common mode filter from the ACT series, packaged in a horizontal 4-PC pad surface-mount footprint (4.50 mm x 3.20 mm, 3.00 mm seated height). It is designed to suppress conducted common mode noise on signal lines — think CAN bus, USB, or LVDS differential pairs where you need to knock down the common-mode hash without distorting the differential signal. Rated for 50 V DC and 150 mA continuous current, with a maximum DC resistance of 2 Ohm, this filter presents 5.8 kOhm of impedance at 10 MHz and 100 µH inductance at 100 kHz. That impedance peak is right where many switching regulators and digital clocks radiate their common-mode noise — the filter acts as a high-impedance wall to those frequencies while passing the low-frequency signal content.
Automotive temperature grade and what it means
The 150°C upper limit covers the hottest spots near the exhaust manifold or turbocharger — a standard 85°C or 105°C part would not survive there.