The STMicroelectronics P6KE400ARL is a unidirectional Zener TVS diode from the P6KE TRANSIL™ series. It provides 600W peak pulse power (10/1000 µs waveform) with a reverse standoff voltage of 342V and a clamping voltage of 706V at the peak pulse current of 5.7A (8/20 µs). Packaged in a DO-15 (DO-204AC) axial leaded through-hole package, it is designed for general-purpose transient overvoltage protection in industrial power supplies, telecom line cards, and AC/DC converter input stages where a single unidirectional channel suffices.
The 600W peak pulse power rating tells you the energy this part can absorb in a single surge event before failing. For a 342V standoff voltage, the device will not conduct appreciably below that level — it stays out of the way during normal operation. The 706V clamping voltage is the maximum voltage the load will see during a transient; if your downstream circuitry cannot tolerate that peak, you need a lower-clamp part or additional filtering. The 5.7A peak pulse current (8/20 µs) gives the surge current capability for short-duration events like lightning or inductive kickback. Capacitance is 360 pF at 1 MHz, which matters if you are protecting a high-speed data line — at 342V standoff this is a power-rail or slow-signal protector, not a high-frequency signal line clamp.
Package and mounting — field-service friendly
The DO-15 axial leaded package is a through-hole part. You can hand-solder it, replace it with basic tools, and visually confirm orientation (the cathode band is marked). No hot-air station needed. For a field-service repair technician, this is a swap-you-can-do-on-site part — just clip the leads, desolder the stubs, and insert the new one. The axial form factor also fits standard 0.4-inch lead spacing on perfboard or PCB.