1.5kW Zener TVS in DO-201 — what the ratings mean for the board
The 1.5KE18-B: The 15.3 V reverse standoff voltage means the part stays in high-impedance mode on a nominal 12 V or 15 V rail and only starts conducting when the transient exceeds 16.2 V (the minimum breakdown). Clamping is specified at 26.46 V at 60.3 A peak pulse current — that 26.46 V ceiling is what the downstream silicon sees during the surge event, so the downstream device's abs-max rating must sit above that number. The DO-201AA / DO-27 axial-lead package (supplier device package DO-201) is a through-hole form factor that handles the thermal pulse of a 1.5 kW surge without lifting the junction above the rated -55°C to 175°C range. The bulk packaging means it ships loose in a bag or tube — no reel, so it feeds into a wave-solder or hand-insertion line, not a pick-and-place.
Obsolete — sourcing reality for the BOM line
Littelfuse lists the 1.5KE18-B as Obsolete. No pin-compatible direct replacement from Littelfuse is documented, so a functional alternative would require a parametric match on standoff voltage, clamping voltage, and package footprint.