TVS protection for 85.5 V rails — SM6T100A in the SM6T TRANSIL family
The STMicroelectronics SM6T100A is a unidirectional transient voltage suppression (TVS) diode from the SM6T TRANSIL series, rated for 600 W peak pulse power (10/1000 µs waveform). It is designed to clamp transients on a nominal 85.5 V continuous rail, with a minimum breakdown voltage of 95 V and a maximum clamping voltage of 178 V at the rated peak pulse current of 22.5 A (8/20 µs waveform).
The 178 V clamping voltage at 22.5 A peak pulse current (8/20 µs) defines the maximum voltage the protected circuit sees during a surge event. For a 85.5 V nominal rail, this provides roughly 2× margin above the operating voltage, which is typical for protecting downstream DC-DC converters or sensitive ICs. The 600 W peak pulse power rating (10/1000 µs) is the energy-handling capability under the standard telecom surge waveform; the actual power capability scales with pulse width, so a shorter 8/20 µs event allows higher peak current. The 95 V minimum breakdown ensures the device does not conduct at the nominal rail voltage, while the 85.5 V reverse standoff is the maximum continuous DC voltage the part can withstand without significant leakage.
Package and mounting — DO-214AA SMB
The SM6T100A is housed in a DO-214AA (SMB) package, a standard surface-mount outline for TVS diodes in the 600 W power class. The SMB footprint is common across the SM6T series, so a board layout designed for one voltage variant can accept others without a PCB change.