78 V standoff, 126 V clamp — the protection window for 48–72 V rails
The SMAJ78CA-13-F: Its 78 V reverse standoff voltage and 126 V clamping point make it a fit for protecting 48 V to 72 V DC buses, industrial signal lines, or telecom power feeds where the normal operating voltage sits below 78 V and the transient must be clamped before reaching 126 V. With a single bidirectional channel, the part clamps both polarities in one package — no need to orient the diode on the board, which simplifies layout for AC-coupled or floating signal pairs.
DO-214AC (SMA) — the standard surface-mount TVS footprint
Housed in the DO-214AC (SMA) package, the SMAJ78CA-13-F uses the same 2-lead footprint as the rest of the SMAJ family. The package is rated for surface-mount assembly and supports the -55°C to 150°C junction temperature range — wide enough for industrial enclosures and under-hood automotive zones where ambient heat soaks the PCB. The 400 W peak pulse rating is tested with the standard 10/1000 µs waveform. At the clamping voltage of 126 V, the peak pulse current is 2.2 A — this tells you the surge the part can absorb before the junction exceeds its thermal limit. For shorter transients (8/20 µs), the effective power capability is higher, but the datasheet's derating curve should guide the margin.