What the 1.5SMC91 is and what the ratings mean
At that pulse width the part absorbs the surge energy and clamps the line before the downstream load sees the overvoltage spike. Reverse standoff of 77.8V sets the continuous working voltage below which the TVS conducts no current. The gap between standoff and clamping voltage is the protection margin — the downstream IC must survive 131.25V for the duration of the event.
Where Zener TVS diodes of this class are used
General-purpose Zener TVS devices protect low-speed signal lines, power rails, and secondary suppression points where the 77.8V standoff fits the rail nominal. The 1.5SMC series is the mid-range peak-pulse class — above the 400W 1.5KE family and below the 3kW 5SMC devices — positioned for board-level protection on industrial and instrumentation panels.
Package, mounting, and sourcing reality
Surface-mount DO-214AB (SMCJ) package on tape-and-reel — compatible with standard SMT assembly lines. Available through independent distribution for existing designs; BOM quantities are quoted to order against an RFQ.