30 V rail protection with a 3 kW punch
The STMicroelectronics SM30T35AY is a unidirectional Zener diode in the DO-214AB SMC package, designed to clamp transients on a 30 V nominal rail. With a peak pulse power rating of 3000 W (3 kW) per the 10/1000 µs waveform, it handles high-energy events like automotive load dump or industrial surge without needing a larger package. The 48.4 V maximum clamping voltage at 62 A peak pulse current gives the downstream circuitry a defined voltage ceiling during a fault. AEC-Q101 qualification covers automotive stress tests. Operating temperature range is -55°C to 175°C.
Reverse standoff voltage is 30 V. Minimum breakdown voltage is 33.3 V. Clamp voltage is 48.4 V. The 3 kW peak pulse rating is tested with a 10/1000 µs waveform — a standard telecom surge shape. In real automotive transients (load dump at 87 V for 400 ms), the energy is lower but the duration longer; derate per the pulse derating curve in the datasheet if your event exceeds 1 ms. The 62 A peak pulse current is the current the diode shunts at the clamp voltage — confirm your source impedance and transient energy stay within the single-pulse SOA.
Package and mounting
The cathode band is marked on the body; the unidirectional channel means one diode per package, anode to ground. MSL 1 (no bake required before reflow) keeps the kitting line moving.
Lifecycle and supply
Base product number is SM30T35. The AY suffix indicates AEC-Q101 grade.