What the clamping specs mean for the BOM
The 1.5SMC22CAHE3/9AT: The 18.8 V reverse standoff means the diode stays transparent on a nominal 12 V or 24 V automotive rail — leakage is negligible until the transient exceeds that threshold. Breakdown starts at 20.9 V minimum, and the clamping voltage is held to 30.6 V at 49 A peak pulse current. For a 24 V truck system, that clamp keeps the downstream electronics within a 36 V absolute-max rating typical of many ECUs and sensors.
The SMC footprint is larger than the SMA/SMB siblings, offering better thermal dissipation for the 1500 W pulse — the copper pad area under the cathode tab should follow the Vishay application note for optimal RthJA.