48V rail protection with AEC-Q101 pedigree
Its 53.3V minimum breakdown voltage and 100V maximum clamping voltage at the peak pulse current define the protection window for downstream electronics in engine control units, transmission controllers, and body modules. The single unidirectional channel in a DO-214AC (SMA) surface-mount package keeps the bill of materials compact for per-rail clamping.
What the 400W rating means for your BOM
For a 48V system — common in mild-hybrid and 48V auxiliary loads — the 23A peak pulse current (8/20µs waveform) gives enough headroom for load-dump and inductive kickback events typical in automotive environments. If your circuit sees repetitive surges near the rated limit, derate the junction temperature from the -55°C to 150°C operating range; the thermal impedance of the SMA pad on a standard 1 oz copper footprint is what governs real-world dissipation.
AEC-Q101 qualification — not just a sticker
The TRANSIL™ series designation from STMicroelectronics confirms the die construction is optimized for fast clamping response, which matters when the protection must fire before the downstream IC sees the overvoltage.
The base product number SM4T56 covers the whole family, so if you need a different voltage variant in the same footprint and qualification, the rest of the SM4TY series is a direct drop-in.