Last-buy status on a proven TVS platform
The 1.5KE100A-E3/51: Vishay has flagged this part as Last Buy, meaning the manufacturer's end-of-life window is open: orders are accepted for existing designs only, and the BOM should plan for a successor or a last-time-buy quantity before the cut-off.
Voltage ratings and what they mean on the rail
The reverse standoff voltage is 85.5V — this is the DC or peak-AC voltage the TVS will not conduct at under normal operation. The breakdown voltage starts at 95V min, so the part stays out of the circuit until a transient pushes the rail above that threshold. That 137V ceiling is what the downstream silicon sees during the surge — the TVS shunts the energy and holds the rail below the 150V-class device breakdowns common in industrial power supplies. The DO-201AA axial body solders into a through-hole board; the leads take the thermal stress of the pulse better than a small SMD package would.
Sourcing this part now
No official successor is listed on the record. For a BOM that cannot tolerate a board spin, the last-time-buy quantity should cover the remaining production run; for new designs, a parametric match in the same TransZorb family with the same DO-201AA footprint is the migration path.