Clamping performance — what 92V means downstream
The reverse standoff of 58.1V sets the normal operating window; once a transient exceeds the 64.6V minimum breakdown, the clamp fires and the TVS limits the peak at 92V with a 16.3A (10/1000 µs) surge current flowing through it. That 92V ceiling is what the protected load sees — the downstream circuit must survive that clamping level, not the raw transient. At 1500W peak pulse rating, the 1.5SMC68AT3G absorbs the surge energy without degradation into the junction-temperature ceiling of 150°C.
Lifecycle — what obsolete means for procurement
Littelfuse has marked the 1.5SMC68AT3G obsolete — no authorized-channel restocking and no stated replacement in the available record. The sourcing path is independent distribution and surplus brokers, where lot traceability and date-code chain of custody become the authentication problem, not just the electrical fit. For a TVS protecting a safety-critical rail, the provenance question is not secondary: a relabeled part with the wrong Vbr punches through at a different voltage and leaves the load exposed.
Package and thermal envelope
The DO-214AB (SMC) package is the standard pick for 1500W TVS in this form factor — the clip-heat-spreader construction handles the thermal transient of a surge event before the junction heats to the 150°C limit. Tape-and-reel and cut-tape packaging support high-volume SMT assembly without a separate tray cost.