What the 1.5SMC68A does and what the ratings mean
The 1.5SMC68A-M3/57T: The standoff voltage of 58.1 V defines the rail it sits across without conducting — the part stays off during normal operation. For a 48 V nominal line (common in industrial 24-60 V power rails), 58.1 V standoff gives reasonable headroom above the steady-state peak. The 92 V clamping ceiling needs to sit below the absolute-max rating of whatever downstream IC or MOSFET it is protecting — if the downstream device can't take 92 V under a surge, the TVS won't save it.
Thermal and mounting notes
The junction temperature rating is -65°C to 150°C (TJ). The DO-214AB package thermal resistance to the board pad matters more than the headline junction rating — the clamping energy rating (1.5 kW) assumes the recommended pad geometry in the datasheet. Skimp on the solder pad and the part unclamps early under a real surge. Tape & Reel packaging suits automated SMT placement. The 1.5SMC68A base product number means the die and construction are consistent across the series — stepping up or down within the family (different standoff voltages) keeps the same footprint.
Vishay lists this part as Active.