400W Zener TVS in a DO-214AC footprint
The SMAJ40A-13: It clamps transients at 64.5V max, with a 40V reverse standoff voltage and a 44.4V minimum breakdown threshold — sized for 40V nominal rails that see occasional surge events. Housed in the DO-214AC (SMA) surface-mount package, it fits standard pick-and-place reflow assembly. The SMA footprint is a common TVS package across the 400W class, so board layouts for this part often accept alternative suppliers without a spin.
For a 40V rail, a 64.5V clamp leaves ~24V of headroom below typical 80V-rated downstream components — a reasonable margin for most industrial and telecom DC buses. Peak pulse power is specified at 400W for a 10/1000µs exponential waveform. That test pulse shape is the industry standard for TVS diode rating — it correlates to the energy in a lightning-induced surge or inductive load dump. Real-world pulse widths shorter than 1000µs allow the device to absorb higher peak power. The junction temperature derating curve (not shown here) typically reduces peak pulse power above 25°C, so a hot enclosure near 85°C ambient cuts the effective surge capacity roughly in half.
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This is a single-channel unidirectional device — it protects one signal or power rail. For bidirectional or multi-channel applications, a different order code from the SMAJ family would apply.