Obsolete — sourcing reality for the 1.5KE20-E3/54
Vishay has marked the 1.5KE20-/54 as Obsolete. For a BOM line that still calls out this DO-201 axial TVS, the supply path runs through independent surplus and excess inventory channels — not the franchised factory pipeline.
What the clamp ratings mean for the circuit
The reverse standoff voltage is 16.2 V, meaning the diode draws negligible leakage below that rail and starts clamping above it. That clamp ceiling decides whether the downstream IC's abs-max rating is protected — a 30 V-rated bus transceiver survives; a 28 V-rated one may not.
The 1.5KE20-/54 comes in the DO-201AA / DO-27 axial-lead package, through-hole mount. The axial body sits in a PTH hole pattern common to the 1.5KE series — the same footprint serves the whole TransZorb family. Tape-and-reel packaging is the standard for automated insertion; the reel quantity matches Vishay's standard 1.5KE reel packing.