Obsolete TVS diode — what the ratings mean for your BOM
The 1.5KE540C: At 486 V reverse standoff, it clamps transients to 777 V maximum while conducting 2 A peak pulse current — this is the surge capacity that protects downstream silicon from lightning-induced or inductive-load transients in a 480 V bus environment.
Lifecycle reality — discontinued, sourced through surplus channels
The 1.5KE540C carries an official Obsolete product status from Littelfuse, meaning the manufacturer no longer produces this device. No successor order code is recorded on the lifecycle entry. For a BOM line locked to this part number, supply now runs through independent surplus and broker channels. Any available stock carries date codes from the last production run, and authenticity verification — marking, package construction, and electrical test — becomes the buyer's screening step before committing to a lot.
Package and board-fit note — DO-201AA axial leaded
Housed in a DO-201AA (DO-27) axial-leaded package, the 1.5KE540C mounts through a single hole in the PCB. The copper lead diameter and body length determine the hole and pad geometry — the datasheet mechanical drawing specifies the lead spacing and the solder fillet clearance for wave or hand-solder assembly. The operating junction temperature range spans -55°C to +175°C, covering industrial and automotive under-hood thermal profiles. At the high end, derate the peak pulse power per the manufacturer's thermal curve — the 1500 W rating holds at 25°C and drops linearly above that.