170V rail protection — what the ratings tell you
Its 189V minimum breakdown voltage guarantees the device starts conducting before the protected circuitry sees an overvoltage, while the 353V maximum clamping at the peak pulse current of 6.5A (8/20µs waveform) defines the worst-case voltage the load must survive. The 400W peak pulse power rating sets the energy-handling budget for a single surge event.
With a single bidirectional channel, this TVS clamps positive and negative transients symmetrically. That saves a diode pair on AC lines or on signal pairs where the polarity is unknown.
Package and footprint — DO-214AC (SMA)
Surface-mount in the DO-214AC (SMA) package, the same footprint used across the SMAJ family. The JEDEC standard land pattern for SMA applies; no special thermal pad or via array needed for the 400W pulse rating, though keeping the trace width adequate for the peak current avoids inductive voltage drop.