TransZorb TVS — what the ratings mean for a protection line
The 1.5KE400-E3/54: A 324 V reverse standoff voltage means the line it protects can run at that DC or AC peak without the diode conducting; clamping starts at 360 V minimum breakdown and hard-clamps at 574 V maximum, limiting the transient energy to 2.6 A peak pulse current.
Obsolete — sourcing through independent channels
Vishay has marked the 1.5KE400-/54 as obsolete. For a BOM that requires this exact clamping voltage and footprint, the DO-201AA axial package is common across many TVS families — a board-level review of the standoff and clamping specs against current-production alternatives is recommended before committing to a last-time-buy quantity.
Through-hole DO-201AA (DO-27) axial package — the lead diameter and body length match the standard 0.100-inch pitch hole pattern on most power-entry PCBs. The 1.5KE series uses a single unidirectional Zener junction; polarity is marked by the cathode band. The 1500 W rating assumes the leads are soldered into a minimum 0.040-inch diameter plated through-hole on a 1 oz copper board; shorter lead length reduces the inductive loop and improves clamping response time.