What the clamp ratings mean on the bench
The 1.5SMC100A-E3/9AT: The 85.5V reverse standoff means it sits across a nominal 85V rail and stays transparent until a transient pushes past the 95V minimum breakdown threshold. When it fires, the clamp holds at 137V maximum — that's the voltage the downstream silicon sees, so the 1500W rating buys you headroom against a 10.9A peak pulse current without the part self-destructing. Single-channel unidirectional construction, so polarity matters on the board — cathode to the protected rail, anode to ground.