1.5 kW bidirectional TVS for 24 V automotive rails
The STMicroelectronics SM15T24CAY is a bidirectional Zener TVS diode from the SM15TY TRANSIL™ series, qualified to AEC-Q101 for automotive applications. It protects a single 24 V nominal rail against transients up to 1.5 kW (10/1000 µs) with a reverse standoff voltage of 20.5 V and a clamping voltage of 42.8 V at the peak pulse current of 234 A (8/20 µs waveform). The DO-214AB (SMC) surface-mount package handles the 150°C junction temperature typical of under-hood or engine-bay environments.
Clamp voltage margin — 20.5 V standoff to 42.8 V clamp
The 22.8 V minimum breakdown voltage sits comfortably above the 20.5 V standoff, so the diode stays off during normal 24 V battery operation including charge float up to about 28 V. When a transient hits, the clamp limits to 42.8 V — that 22 V of headroom between standoff and clamp is what keeps a downstream ECU's 40 V-rated input MOSFETs or DC-DC converter alive during a load-dump pulse. For a 12 V system this part is overkill; it is sized for 24 V truck, bus, or heavy-equipment architectures.
150°C junction — under-hood capable
Rated operating junction temperature from -40°C to 150°C. That 150°C ceiling matches the AEC-Q101 Grade 0 profile, meaning this part can sit on an engine control unit PCB or inside a transmission controller where ambient regularly hits 125°C and self-heating adds another 25°C. No derating curve needed at 125°C ambient as long as the PCB copper and via count carry the heat from the SMC package.
The base product number SM15T24 covers the unidirectional and bidirectional variants across the family, so if a future design needs the unidirectional version the supply chain stays on the same qualification and package footprint.