Standoff, breakdown, and clamping — the working window
The 1.5SMC75CAHE3/57T: The reverse standoff of 64.1 V typ sets the continuous working voltage below which the TVS is off and draws only leakage. Breakdown kicks in no lower than 71.3 V min, and during a surge the clamping voltage at the peak pulse current does not exceed 104 V max. That roughly 40 V window between standoff and clamping is where the downstream circuitry sees protection headroom during automotive load-dump or inductive dump transients. Peak pulse current at that same waveform is 14.6 A. Verify your surge waveform matches the 10/1000 µs shape; a faster or slower transient changes the energy the part sees.
Junction temperature and the automotive thermal envelope
Junction operating range runs to 150°C, starting at -65°C. That covers the under-hood profile — engine-bayECU, chassis-node, and 24V commercial-vehicle rails all sit within that window. The AEC-Q101 qualification means the part passed the temperature-cycle, bias, and power-temperature stress screens required for automotive safety-critical deployments.