600W peak pulse power in a DO-214AA footprint
The STMicroelectronics SM6T6V8A is a unidirectional TRANSIL™ TVS diode rated for 600W peak pulse power (10/1000µs waveform), with a 5.8V reverse standoff voltage and a 6.45V minimum breakdown. This is a single-channel device in the DO-214AA (SMB) surface-mount package, intended for general-purpose overvoltage protection on low-voltage DC rails.
The base product number is SM6T6, so other voltage variants in the same family share the same footprint and power rating.
The 5.8V reverse standoff voltage means this diode will not conduct at normal 5V or 3.3V rail voltages, but it will start to avalanche at 6.45V minimum. The 600W rating is for an 8/20µs waveform; the same device is also rated for 298A peak pulse current under that condition.