The STMicroelectronics 1.5KE33ARL is a unidirectional Zener-based transient voltage suppressor from the TRANSIL™ 1.5KE series. It is a through-hole device in a DO-201AA (DO-27) axial-lead package, rated for 1500W peak pulse power per the 10/1000µs waveform. The 28.2V reverse standoff voltage and 31.4V minimum breakdown voltage place it in the 28V rail protection class, with a maximum clamping voltage of 59V at the rated peak pulse current of 169A (8/20µs waveform). Typical applications include general-purpose surge protection on power supply rails, industrial control inputs, and telecom line cards where a single unidirectional suppressor handles one polarity.
For a 28V nominal rail, the 28.2V standoff voltage means the TVS does not conduct during normal operation, while the 31.4V minimum breakdown ensures it starts clamping before the rail exceeds safe limits. The 59V maximum clamping voltage at 169A (8/20µs) is the worst-case voltage the protected circuitry must survive — if the downstream components are rated below that, a lower-clamping part or additional protection stage is needed. The 2700pF capacitance at 1MHz is significant: on high-speed data lines (Ethernet, USB 2.0, CAN) that capacitance will load the signal and may degrade edge rates or cause reflections, so this part is better suited to power rails and slower I/O than to high-frequency interfaces.