The 1.5SMCJ14CA_R1_00001: At 10/1000 µs the 64.7A peak pulse current clamps to 23.2V maximum — the standoff rating of 14V means the diode sits idle below the 15.6V breakdown minimum during normal operation and activates only on a surge event, clamping the overvoltage before it reaches the protected circuit.
Clamping and standoff — the protection window
The standoff-to-breakdown window is tight: 14V typical standoff vs 15.6V minimum breakdown gives roughly 1.6V of headroom. For a 12V rail this is fine — the diode stays off under normal operation. For a 13.8V automotive supply, confirm the peak transient profile stays below 15.6V, otherwise a part with a higher standoff rating is the right fit.