What this 36V bidirectional TVS protects — and where it sits
The STMicroelectronics SM30T42CAY is a 3000W peak-pulse-power bidirectional Zener TVS diode in a SMC surface-mount package, qualified to AEC-Q101 for automotive applications. Its 36V reverse standoff voltage fits 24V nominal vehicle power buses, 36V supply rails, and 42V load-dump transients.
Peak pulse power — what 3000W means in a real transient
The 3000W peak pulse power rating (10/1000µs waveform) is the headline surge capability. For a 24V system where load-dump can reach 60V to 80V for several hundred milliseconds, this part absorbs the energy without failing short. The 48.4A peak pulse current at the 58.1V clamp voltage means the protected rail sees a hard voltage ceiling during the surge. Because the device is bidirectional, it clamps both positive and negative transients equally — no polarity concern when installing on AC-coupled signal lines or power buses that may reverse-bias during a fault.
AEC-Q101 qualification and the automotive supply chain
AEC-Q101 qualification means the SM30T42CAY has passed the automotive discrete stress tests: pre- and post-stress electrical parameters, high-temperature reverse bias (HTRB), temperature cycling, and moisture resistance. For a Tier-1 or OEM program, this qualification eliminates the need for additional PPAP-level discrete testing.
Package and footprint — DO-214AB (SMC)
The SMC body fits into the same land pattern as other SMC-packaged TVS diodes. The bidirectional construction means the cathode/anode marking is absent — both directions are identical, simplifying pick-and-place orientation.