Obsolete status and what it means for your BOM
The 1.5KE440-B: This part is officially obsolete per the manufacturer's lifecycle record. That means Littelfuse no longer manufactures it, and no last-time-buy window remains open through the factory channel. Any stock you find is from existing inventory — date codes and provenance need verification at the point of sourcing.
Protection specifications for circuit design
It clamps transient overvoltages at a maximum of 632.1V when conducting its peak pulse current of 2.5A. The reverse standoff voltage is 376V, meaning the device does not conduct appreciably below this level. Breakdown occurs at a minimum of 396V, triggering the clamping action that protects downstream circuitry.
Package and board integration
Housed in a DO-201AA / DO-27 axial leaded package (supplier device package DO-201), it is a through-hole component intended for hand-insertion or wave-solder assembly. The axial leads require drilled plated-through holes on the PCB. The bulk packaging means parts are supplied loose in a bag or tube, not on tape and reel — factor this into your pick-and-place planning if you are mixing through-hole with SMT assembly. Note that the spec sheet indicates no power line protection — this device is designed for signal or low-power rail transient suppression, not for continuous overvoltage clamping on mains or high-current power buses.