1500W bidirectional Zener TVS for 73.7V rails
The 1.5KE91CHE3/54: Its 73.7V reverse standoff voltage protects 72V nominal rails from transients up to 131V clamping at 11.5A (10/1000µs waveform). Bidirectional construction means a single device clamps both positive and negative surges — useful for AC-coupled signal lines or power rails where reverse polarity is possible, saving one diode per protected line.
AEC-Q101 and the 175°C operating ceiling
Vishay lists this part as Obsolete. For new designs or BOM continuity, the closest active alternative would need to match the 73.7V standoff, 1500W peak pulse, bidirectional configuration, and AEC-Q101 grade — a parametric search against the 1.5KE family is the starting point.
Through-hole DO-201AA footprint and board-fit note
The DO-201AA axial-lead package (also known as DO-27) is a through-hole form factor with a 0.052-inch lead diameter. It requires a 0.040-inch plated through-hole on the PCB — a legacy footprint that is still common in automotive power distribution boxes and industrial control boards where wave solder is the primary assembly method. No power line protection feature is claimed — this is a standalone TVS, not a integrated filter. The 11.5A peak pulse current at 131V clamping defines the maximum surge the diode can absorb before breakdown; for higher energy events, a larger package or parallel device is needed.