500 W Zener TVS in an Axial Package
It clamps a transient at 26.5 V maximum when the peak current hits 107 A under the 8/20 µs waveform. That 26.5 V clamp ceiling is what the downstream silicon sees — if your rail is a 15 V bus, the 1N6464 holds the surge well below a typical 30 V absolute-max of a downstream regulator.
Breakdown and Clamp Window
The reverse standoff voltage is 15 V — the rail voltage the part leaves alone during normal operation. Breakdown starts at 16.4 V minimum, so on a 15 V supply the diode begins conducting about 1.4 V above the rail, well before the clamp voltage of 26.5 V. That gap between standoff and breakdown gives margin for steady-state ripple without the diode chewing up leakage current.
Thermal and Package Reality
The part comes in an axial-lead through-hole package (B, Axial) — the leads carry the surge current into the PCB, so the trace width from the anode and cathode pads to the protected rail needs to handle the 107 A peak without fusing.