400W peak pulse power in a DO-214AC package
It is a unidirectional Zener-type suppressor in a DO-214AC (SMA) surface-mount package, rated for general-purpose overvoltage protection across a -55°C to 150°C operating junction temperature range.
What the 20V standoff and 42.8V clamp mean for your rail
When a transient exceeds the 22.2V breakdown threshold, the diode avalanches and clamps the surge to 42.8V maximum at the 54A peak pulse current (8/20µs waveform). That clamp voltage is what the protected device sees; a 42.8V clamp on a 20V rail means the downstream components need a 42.8V or higher absolute maximum rating to survive the event.