1500W Zener TVS — 47.8V standoff, 77V clamp
The 1.5SMC56A-M3/9AT: It protects a 47.8V nominal rail — the reverse standoff voltage — by breaking down at 53.2V min and clamping transients to 77V max at the 19.5A peak pulse current. This is a transient suppressor, not a voltage regulator: the Zener breakdown is used for its fast clamping action, not for DC regulation. The 1500W rating means it can absorb a single 10/1000 µs surge of that energy without damage; for shorter pulses the peak power is higher, for longer pulses it derates per the datasheet curve.
The package is reflow-solderable and, with care, hand-solderable — the large tab on the cathode side provides a good thermal path to the PCB copper pour, which is essential for dissipating the pulse energy. The wide temperature margin means the clamping voltage and leakage current remain within spec across the full range.
The part is supplied on Tape & Reel (TR) for automated pick-and-place assembly.