Automotive-grade 1500 W surge clamp
The 1.5SMC39AHE3/9AT: This is the standard for under-hood and chassis electronics where a single surge failure could strand a vehicle.
Breakdown and clamping — where the protection starts
Minimum breakdown voltage is 37.1 V, so the diode begins conducting at roughly that threshold. The 33.3 V standoff rating means the circuit sees negligible leakage up to that voltage; the TVS stays invisible until a transient exceeds the standoff level. Maximum clamping voltage of 53.9 V at 27.8 A defines the worst-case voltage the protected circuit will see during a 10/1000 µs surge.
The operating temperature span of -65°C to +150°C covers the full automotive ambient range plus self-heating margin from the surge pulse.