40V rail clamp, 600W surge rating
Its 600W peak pulse power rating (10/1000µs waveform) means it can absorb a surge of 8.4A before the clamping voltage reaches 71.4V max.
Breakdown window and clamping margin
Minimum breakdown voltage is 44.4V, which gives a 4.4V guard band above the 40V standoff. That margin matters when the rail sits at 40V nominal with a 5% tolerance — the TVS stays off during normal operation and only fires when a transient pushes the line above 44.4V. The 71.4V max clamping voltage at 8.4A peak pulse current defines the voltage the downstream circuitry must survive; a 40V-rated capacitor on that rail would need a higher voltage rating to ride through the clamp event.
Active production, Tape & Reel delivery
Microchip lists the SMBJ40CE3/TR13 as Active.