51 V rail protection in a DO-214AC body
The reverse standoff voltage of 51 V means it stays off the bus under normal conditions, and the minimum breakdown voltage of 56.7 V guarantees avalanche onset before the rail sees damaging overvoltage. Peak pulse power is rated at 500 W for the standard 10/1000 µs waveform — enough to handle common industrial surge events on a 48 V or 51 V supply.
Clamping voltage and surge current — the real stress numbers
That 82.4 V ceiling tells you what the downstream silicon sees during a strike — if your 51 V rail feeds a converter rated for 80 V absolute max, this diode leaves no margin; you need a lower-clamp part or a secondary protection stage.
Active production, surface-mount reel
RoHS compliance is standard for the suffix; no lead-free transition risk.
The DO-214AC footprint is shared by many 500 W TVS diodes from other vendors, but the breakdown and clamping thresholds are specific to the SMAJ51 family. If you are replacing a competitor's 51 V TVS in the same package, confirm the breakdown min matches your rail tolerance.