Clamping voltage and surge current — the real protection envelope
The 1.5KE43: For a 36.8 V rail, this provides roughly 1.7× headroom — enough to keep downstream 40 V-rated components within their avalanche margin. The 1500 W peak pulse rating is the product of clamping voltage and peak current at the test waveform. Derating applies at elevated ambient temperatures per the standard power-temperature curve for axial-leaded TVS diodes.
Obsolete — sourcing through independent channels
Littelfuse lists the 1.5KE43 as obsolete. For a BOM line that requires this specific clamping voltage and package, the 1.5KE43 remains available on a quoted-to-order basis.