What a TVS diode built on a Zener junction means
The 1.5SMC91CA: That Zener construction gives it a defined, repeatable clamping characteristic.
The standoff, breakdown, and clamping chain
77.8 V reverse standoff is the maximum voltage the line can sit at continuously without the TVS conducting. The breakdown minimum of 86.5 V is where the junction begins to avalanche and the clamp activates. A longer or higher-energy waveform will derate the effective clamping capability.
Thermal and package fit
The DO-214AB (SMCJ) package is the standard surface-mount footprint for this power class. It solders in a standard reflow or wave profile; the cathode bar on the body aligns with the polarity markings and must be correctly oriented — a reversed TVS will conduct continuously and fail. Tape-and-reel and cut-tape packaging are both available, so the part suits both high-volume SMT assembly and low-quantity prototype runs without a minimum order penalty. The series is rated for general-purpose applications and does not carry a dedicated power-line-protection certification — for AC mains protection you need a part certified to IEC 61643-11 or equivalent; the 1.5SMC91CA is the right fit for DC bus, signal line, or telecommunications node protection.
Sourcing posture
Available through independent distribution; quoting and lead time confirmed against the BOM quantity at RFQ.