The 1.5SMC440A-E3/9AT: Vishay has marked the 1.5SMC440A-/9AT as Obsolete. For existing BOM lines, this part is sourced through independent distribution channels.
Zener TVS — 1500 W peak pulse, 376 V standoff
The minimum breakdown voltage is 418 V, ensuring the device begins conducting before the protected circuit's voltage rating is exceeded.
DO-214AB (SMC) — surface-mount board fit
Housed in a DO-214AB (SMC) package, this TVS is designed for reflow soldering onto a standard surface-mount PCB footprint. The single unidirectional channel means the cathode is tied to the protected rail; the anode connects to ground. It is not intended for AC power line protection.