The STMicroelectronics SM6T10A is a unidirectional TRANSIL™ TVS diode from the SM6T series, designed to clamp transient overvoltages on a 8.55 V nominal rail. Rated for 600 W peak pulse power (10/1000 µs waveform), it breaks down at a minimum of 9.5 V and clamps at 18.6 V maximum, protecting downstream circuitry from ESD, surge, and inductive load dumps.
The 8.55 V reverse standoff voltage is the maximum DC or peak-AC voltage the protected line can carry without the diode conducting; above that, the 9.5 V minimum breakdown triggers avalanche conduction. The 18.6 V clamping voltage is the peak voltage the load sees during a pulse — ensure downstream components have at least that margin.