Transient protection for legacy board designs
The 1.5KE43ARL4G: It clamps transients at 59.3 V maximum while conducting 25.3 A peak pulse current, protecting downstream circuitry on a 36.8 V nominal rail. The DO-201AD axial package suits through-hole mounting on boards where a replacement TVS must drop into an existing footprint without layout changes.
Parametric fit for 36.8 V rail protection
Breakdown occurs at 40.9 V minimum, ensuring the TVS does not conduct during normal operation. The 59.3 V clamping voltage at 25.3 A peak pulse current defines the maximum voltage the load sees during a transient event. For a 36 V bus, this clamp margin is adequate for most secondary protection stages but should be verified against the downstream component's absolute maximum ratings.
Obsolete status and sourcing path
Littelfuse has designated the 1.5KE43ARL4G as obsolete. The Mosorb series includes functionally similar Zener TVS diodes in the same DO-201AD package with different standoff voltages. A parametric search on the 36.8 V standoff and 1500 W rating may identify a currently active alternative, but no pin-compatible drop-in replacement is documented in this record.