What this TVS diode protects and where it fits
The 1.5SMC51AT3G: It clamps a 43.6 V nominal rail — the reverse standoff voltage — and begins conducting at 48.5 V breakdown, limiting the surge to 70.1 V max at 21.4 A peak pulse current.
Obsolete — sourcing reality for the BOM line
For a BOM line that already specifies this part, the supply path runs through independent distribution and surplus channels — quantities are lot-specific and confirmed at RFQ. If the design is still in development, a pin-compatible TVS from the same 1.5SMC family with a similar standoff voltage (e.g., a 43.6 V or adjacent rating) may be a drop-in alternative, but the exact clamping and breakdown window should be verified against the original protection requirement.
Temperature range and package — board-fit notes
No special ESD precautions beyond normal handling for a surface-mount component.