150V rail clamp — Zener TVS in a standard SMA footprint
Its 167V minimum breakdown voltage and 268V maximum clamping voltage define the protection window — the transient gets clipped before it reaches downstream silicon. That pulse power rating is typical for a DO-214AC (SMA) package — the limiting factor is the copper pad area under the cathode tab, which sets the thermal impedance to the board.
The wide range also means the reverse leakage current — which rises sharply above 100°C — needs a thermal budget check if the ambient near the TVS exceeds 85°C.
Microchip lists the SMAJ150E3/TR13 as Active. The base product number is SMAJ150, so other package or voltage variants share the same family footprint.