Transient protection for 213V rails
The STMicroelectronics 1.5KE250A is a unidirectional TRANSIL™ TVS diode from the 1.5KE series, designed to clamp transients on DC power rails and signal lines in general-purpose industrial and telecom equipment. It delivers 1500W peak pulse power per the 10/1000µs waveform, with a reverse standoff voltage of 213V and a minimum breakdown voltage of 237V. The clamping voltage is held to 442V at the peak pulse current of 23A (8/20µs waveform). This part is through-hole mounted in a DO-201AA (DO-27) axial-lead package, suited for board-level surge protection where a single unidirectional device protects one polarity rail.
The 237V minimum breakdown voltage is the threshold where the device starts to avalanche; the 442V clamping voltage at 23A peak pulse current is the maximum voltage the protected circuit sees during a transient event. A downstream component rated for at least 442V is needed to survive the clamp. The 1500W peak pulse power rating (10/1000µs) gives the energy-handling capability for a single surge — derate for repetitive events or higher ambient temperatures. The unidirectional channel means this device protects one polarity; for AC or bidirectional lines, the 1.5KE250CA (bidirectional variant) would be the correct choice.