600 W peak pulse, 110 V standoff — the clamping decision
The SMBJ110A-13: The 122 V minimum breakdown voltage means it stays out of the way during normal operation and only conducts when the line exceeds that threshold. The 600 W rating is the product of that clamp voltage and current, so a shorter pulse (8/20 µs) allows a higher peak current before the device reaches its thermal limit.
DO-214AA SMB — footprint and thermal path
Housed in the DO-214AA (SMB) package, the SMBJ110A-13 is a surface-mount device with a single unidirectional channel. The cathode tab on the SMB package carries the bulk of the heat to the PCB copper — the board layout's pad area under the tab directly sets the junction-to-ambient thermal resistance. The operating junction temperature range spans -55°C to 150°C, covering industrial and some automotive under-hood environments.