Its reverse standoff voltage of 36V means it will not conduct at nominal rail voltage, so it sits across the line without loading it. When a transient exceeds the 40V minimum breakdown, the diode clamps the spike to 58.1V maximum while shunting 8.6A of peak pulse current — that 58.1V ceiling is the number to check against the absolute maximum rating of the IC you are protecting.
Peak pulse power and temperature reach
No power line protection means it is not intended for AC mains; keep it on DC signal or low-voltage power buses.
The DO-214AC (SMA) package is a standard footprint shared across the SMAJ family, so if you need a different voltage rating, the base product number SMAJ36 lets you step to 5V, 12V, 24V, or other values without a board respin.