28V rail clamp — what the 400W rating buys you
Its 400W peak pulse power rating means it can absorb a 39A peak pulse current without failing — useful for protecting a 24V DC bus or a 28V supply line in industrial or telecom gear.
Breakdown and clamping — the numbers that matter
Minimum breakdown voltage is 31.1V, so the part starts conducting before the rail sees damaging overvoltage. Maximum clamping voltage at rated Ipp is 59V — that is the peak voltage the downstream circuitry must survive. The 28V reverse standoff is the continuous DC level the TVS blocks without leakage becoming a problem.
Package and mounting — DO-214AC SMA
Surface-mount DO-214AC (SMA) package, supplied on Tape & Reel or Cut Tape. The small footprint fits tight layouts on a 2-layer board; the cathode band identifies the unidirectional orientation. No power line protection feature — this is a signal/DC rail clamp, not an AC mains suppressor.