Transient protection for a 30.8 V rail
The 1.5KE36CA-E3/51: The bidirectional construction (single channel) protects both polarities from a single device, which simplifies BOM layout for AC-coupled signal lines or bipolar DC supplies where the return path can swing negative relative to ground.
Voltage thresholds and the protection window
For a 36 V bus, the margin between the operating rail and the breakdown knee is about 3.4 V, which is tight but workable if the rail is well-regulated. The through-hole DO-201AA / DO-27 axial package (1.5KE footprint) is a legacy form factor still widely used in high-reliability and retrofit designs where the board already has the hole pattern.
Last Buy — sourcing for the BOM line
Vishay has placed the 1.5KE36CA-/51 in Last Buy status. This means the manufacturer is no longer accepting volume orders for ongoing production; the remaining stock in the distribution channel is the final inventory. If a replacement is needed for a new design, a parametric search for a bidirectional TVS with a 30.8 V standoff, 1500 W peak pulse, and DO-201 package will yield candidates from the same TransZorb family or competing lines. The existing board layout and hole pattern are the binding constraints.