What this TVS diode does on a 15V rail
Its reverse standoff voltage of 15V means it stays out of the circuit during normal operation, only conducting when the line sees a spike above its breakdown threshold of 16.7V min. Rated for 600W peak pulse power under the 10/1000µs waveform, it can handle a peak pulse current of 22.3A before the clamping voltage hits 26.9V max. That is enough margin to protect a 15V supply from a nearby lightning surge or inductive kick without letting the rail exceed most downstream ICs' absolute maximum. Single unidirectional channel — one diode per package, cathode band marked.
Package and temperature range for field fit
Housed in a DO-214AA (SMB) package, surface-mount with a standard footprint. The SMBJ (DO-214AA) supplier device package is the same body as many other SMBJ-series parts — if you have a 15V TVS in that footprint on the board, this drops in without a layout change. Operating temperature spans -65°C to 150°C — wide enough for outdoor telecom cabinets, under-hood automotive (if not AEC-Q101, but the temp range covers it), or industrial control panels.
Listed as Active by Microchip Technology. The base product number SMBJ15 is a standard JEDEC-registered series, so second-source equivalents from other manufacturers exist (e.g., Littelfuse, Bourns, Vishay) with the same DO-214AA footprint and 15V standoff. Supplied in Tape & Reel — 3000 pieces per reel typical for SMB packages. That suits automated pick-and-place assembly; no manual handling needed.