The SMCJ78CAQ-13-F: That 1.5 kW rating means it can clamp a transient up to 11.4 A peak pulse current without exceeding the 126 V clamping voltage — the voltage the load sees during the event. The reverse standoff voltage is 78 V, so it sits across a 78 V nominal rail and stays transparent until the transient exceeds the minimum breakdown voltage of 86.7 V. Below that threshold, the diode draws negligible leakage; above it, the avalanche action shunts the surge to ground.
Automotive AEC-Q101 — what the grade certifies
This part belongs to the Automotive, AEC-Q101, SMCJ series.
Housed in a DO-214AB (SMC) surface-mount package, the SMCJ78CAQ-13-F is a standard footprint for high-power TVS diodes. The SMC package's large copper tab on the cathode side (for unidirectional versions) or the body itself (bidirectional) conducts heat into the PCB copper plane — the 1500 W rating assumes a low-thermal-resistance board layout with adequate pad area. Supplied on Tape & Reel, it is compatible with automated pick-and-place assembly. The bidirectional configuration (single channel) means the same device clamps positive and negative transients, so orientation on the board does not matter — one part number covers both polarities.