TransZorb® Zener clamp — 300 V rail, 1.5 kW pulse
The 1.5SMC350A-M3/57T: The reverse standoff voltage of 300 V means the diode stays high-impedance under normal operating conditions, only conducting when the line exceeds that threshold.
The supplier device package is listed as DO-214AB (SMCJ), which shares the same footprint as the standard SMC package — a single PCB layout serves both markings. Surface-mount assembly with Tape & Reel packaging is available for volume production.
Vishay lists this part as Active in its product status.