What this common-mode filter does on a signal pair
The TDK ACM2012E-900-2P-T00 is a 2-line common-mode filter from the ACM-E series, designed to suppress conducted noise on differential signal pairs in the 100 MHz band. It presents 90 Ohms of common-mode impedance at 100 MHz, which knocks down common-mode noise on a USB, LVDS, or Ethernet differential pair without attenuating the differential signal itself. The 330 mA continuous current rating and 350 mOhm max DCR mean it handles moderate-speed data lines without significant voltage drop — fine for a 5 V supply rail but the DCR will drop about 115 mV at full rated current.
Package, footprint, and board-fit
The 4-pad configuration is common for common-mode filters in this footprint — the inner two pads are the input/output pair, the outer pads are ground reference on the PCB.
No pin-compatible successor is recorded from TDK for this order code — the ACM-E series has been superseded by newer families that may share the same footprint but differ in impedance profile. Available through independent surplus and broker channels; date codes and lot traceability are confirmed per RFQ. This is a single-source risk item — a board spin may be required if a replacement is needed long-term.