1500 W TVS for 48 V / 60 V rails — what it protects
It clamps transients on 70 V standoff rails, with 77.8 V minimum breakdown and 146 V maximum clamping voltage.
AEC-Q101 and the TRANSIL™ series — why it matters for automotive BOMs
This part carries AEC-Q101 qualification, the automotive stress-test standard for discrete semiconductors. That means it passed the full suite of reliability tests — high-temperature reverse bias, temperature cycling, and surge endurance — required for Tier-1 automotive modules. The SM15T82AY is part of the SM15TY series, ST's TRANSIL™ TVS line optimized for automotive transient protection. No successor or replacement has been announced; for dual-sourcing, look at other AEC-Q101 1500 W TVS diodes in the same DO-214AB footprint with a 70 V standoff rating.
Peak pulse current and clamping — sizing the protection
The SM15T82AY is rated for 69 A peak pulse current under the 8/20 µs waveform, which is the standard for ESD and lightning-surge testing per IEC 61000-4-5. The 146 V clamping voltage at that current is the ceiling the protected bus sees — a downstream 100 V-rated MOSFET or 80 V-rated capacitor would be at risk if the clamping voltage exceeds its breakdown. For a 48 V nominal rail (e.g., automotive load-dump or industrial 48 V PoE), the 70 V standoff provides enough margin to avoid false triggering from normal ripple, while the 1500 W rating handles the energy from a typical load-dump pulse. Note that power line protection is not specified (the part is unidirectional), so it is intended for DC rails with a known polarity, not AC mains.