Protection window: standoff, breakdown, and clamping
The 1.5SMCJ6.5CA: The 6.5V reverse standoff is the voltage the TVS diode ignores in normal operation — the circuit runs below it and the diode presents a high-impedance leak path. This is a board-level power-rail clamp, not a busbar protector.
Junction temperature and thermal margin
Rated to 150°C junction temperature — most consumer-grade TVS parts top out at 125°C. The extra 25°C of thermal margin matters in enclosed panels or power-supply enclosures where ambient runs hot and the transient events are frequent enough that average dissipation adds up across the diode's thermal time constant.