What the clamping spec means for your rail
The 1.5SMC75A-M3/57T is a unidirectional TVS Zener — Vishay calls this the TransZorb® series — in the DO-214AB (SMC) surface-mount package. The standoff voltage is 64.1 V typical, the minimum breakdown sits at 71.3 V, and under a 10/1000 µs surge the clamping ceiling is 104 V at 14.6 A peak pulse. At that point the device dissipates 1.5 kW for the surge duration, which is what defines the clamping node your downstream circuitry sees. A 75-V standoff rating means it sits across a 48-V nominal rail and clamps the transient before the downstream MOSFET or bus voltage sees dangerous overstress.
SMC package for wave or reflow assembly
The DO-214AB body accepts standard reflow profiles — the cathode bar on the sleeve marks polarity and must face the line to be protected. The Tj max of 150 °C and the operating range down to -65 °C cover automotive under-hood and industrial outdoor enclosures. Termination finish is matte tin per the standard series finish; confirm the board-level thermal pad clearance against your reflow thermal map if the part sits near high-dissipation neighbours.