Protection threshold — what the standoff and clamping voltages mean
The 1.5SMC91AHE3_A/H: The 1.5 kW peak pulse rating makes this part the primary overvoltage clamp on a 77.8 V rail — a transient that exceeds the 86.5 V breakdown threshold causes the TVS to crowbar, limiting the clamped voltage at the protected node to 125 V maximum. The 77.8 V reverse standoff is the working voltage where the TVS stays off during normal operation — it is not a breakdown or a protection threshold, it is the ceiling for clean rail conditions.
Automotive qualification and temperature margin
AEC-Q101 places this in the automotive discrete semiconductor qualification flow — temperature cycling, humidity bias, and surge stress are screened to the grade level that automotive ECU suppliers require before sign-off.
Package and polarity for board assembly
The DO-214AB (SMCJ) package is the standard pick-and-place compatible outline for this series — the cathode stripe marks polarity on the unidirectional device, and the pad layout must match the polarity for the clamp to function in the correct direction. Tape & Reel packaging supports high-volume assembly runs without tray handling.