TVS Zener — clamping voltage and peak pulse rating
The 1.5SMC91CA_R1_00001: Reverse standoff is 77.8 V typical; the diode stays reverse-biased and invisible to the circuit until the transient pushes the line above that threshold, at which point it clamps within its rated response window.
Junction temperature and package for general-purpose boards
Rated junction temperature runs to 150 °C, meaning the diode tolerates significant self-heating from repeated transients without accelerated wear — this thermal margin is the practical reason a general-purpose TVS outlasts a cheaper lower-rated part in any circuit that sees irregular surge events. The DO-214AB SMC package is the standard industry footprint for this series; it lands on the same pad geometry as competitor parts in the 1.5SMC family, so the board layout carries over without spin.