What the clamping voltage means on a 154V rail
The 1.5SMC180A: The 171V minimum breakdown voltage sits above the 154V reverse standoff, so the part stays transparent during normal operation and only conducts when the line exceeds that threshold. That 246V ceiling tells you what the downstream silicon sees during a surge — a 48V power supply on the same rail needs a 250V-rated input stage to survive.
Housed in the DO-214AB (SMC) package, also listed as the supplier device package SMCJ. This is the standard footprint for 1500W TVS diodes in this voltage class — the same pad layout accepts the 1.5SMC series across the full voltage range, so a single copper pattern serves the whole BOM family. Surface-mount only; no through-hole variant exists. The 150°C TJ rating means the die temperature can climb during a pulse train without immediate failure, but the long-term reliability at elevated ambient follows the standard Arrhenius derating.