The STMicroelectronics SM6T36A is a unidirectional TRANSIL™ TVS diode in the SM6T series, rated for 600W peak pulse power (10/1000µs waveform). Its 30.8V reverse standoff voltage means it stays off the bus up to that DC level, clamping at 64.3V when the surge hits. Typical application is general-purpose transient protection on power or signal lines where the working voltage sits at or below 30.8V.
Clamping voltage and breakdown — sizing the protection window
The minimum breakdown voltage is 34.2V, so the device starts conducting between 34.2V and the clamping ceiling of 64.3V. That 30V window between standoff and clamp gives the designer headroom for normal rail transients without nuisance triggering, while still limiting the let-through voltage during a surge. The 600W rating assumes a 10/1000µs pulse — derate for shorter or repetitive events per the thermal curve.
No power line protection is claimed — this is a signal or low-power rail protector, not a mains-side device.