What this TVS diode protects and where it sits
It clamps transients at 126V max while conducting 4.7A peak pulse current. Bidirectional construction means a single device handles both positive and negative surges — no polarity concern on AC signal lines, telecom pairs, or bipolar power rails.
Active lifecycle — no last-time-buy clock
Microchip lists the SMBJ78CAE3/TR13 as Active.
Housed in the DO-214AA (SMB) surface-mount package, the SMBJ78CAE3/TR13 shares the same footprint as the SMBJ (DO-214AA) supplier device package. The SMB body is smaller than the SMC but larger than the SOD-123 — it balances surge capability with board area. The copper pad area under the cathode tab on the PCB sets the thermal resistance; a 1 oz copper pad of at least 25 mm² per the typical layout keeps junction temperature rise within limits during repetitive surge events.