It is rated for 1500W peak pulse power (10/1000µs waveform) and has a reverse standoff voltage of 10.2V, meaning it stays off the line below that level and starts conducting when the voltage exceeds the 11.4V breakdown threshold. The DO-201AD axial package is a through-hole form factor that handles the thermal energy of a 1500W pulse without cracking the epoxy.
Why the 1500W rating matters for your rail protection
For a 12V nominal rail (10.2V standoff), this translates to a peak pulse current of 90A. Compare that to a lower-power 600W TVS in the same voltage class: the 1.5KE12ARL4 can handle roughly 2.5× the surge current, which matters if your load has large input capacitors or long cable runs that store inductive energy. The 10.2V reverse standoff is the maximum DC voltage the diode can sit across without conducting leakage current. If your rail is 12V nominal, this part is a good fit; for a 5V rail it would never trigger, and for a 15V rail it would be in continuous breakdown and fail thermally. The 11.4V breakdown minimum gives a guard band of about 1.2V above the standoff, which accounts for tolerance and temperature drift.
This means the manufacturer has stopped production and there is no guaranteed future supply. If you have an active BOM line using this part, you need to either secure a last-time buy (LTB) from remaining distributor inventory or qualify a replacement. Because the part is obsolete, we source it on a per-RFQ basis from our network of franchised and independent distributors. If you need a drop-in replacement, the 1.5KE12A (without the RL4 suffix) in the same DO-201AD package is a common cross-reference, but verify the breakdown and clamping voltages match your design margin.