What the 400 W peak pulse rating means for your protection design
The SMAJ40A-13-F: That 400 W figure is the product of the clamping voltage and the peak pulse current — at the 64.5 V clamp, the device handles 6.2 A of surge current before the junction exceeds its thermal limit. For a 40 V rail, the 44.4 V minimum breakdown ensures the diode stays off during normal operation and only conducts when a transient pushes the line above that threshold.
Package and board-fit: DO-214AC (SMA) surface mount
The DO-214AC (SMA) package is a standard surface-mount footprint with a 2.6 mm body width and 4.3 mm length. The SMAJ40A-13-F ships in Tape & Reel (TR) or Cut Tape (CT) — the -13-F suffix indicates the reel quantity and lead-free finish. The SMA footprint is shared across the entire SMAJ40 family, so a single PCB pad layout serves the 5 V through 170 V variants without a board spin.