Transient protection for 22V rails
The SMBJ22A-13-F: The 600 W rating is the peak pulse power dissipation for an 8/20 µs or 10/1000 µs surge; derate linearly above 25 °C per the datasheet curve. For a 22 V bus, the clamping margin to downstream component abs-max ratings is roughly 13.5 V — enough headroom for most 30 V-rated ICs on a 24 V supply.
The SMB package is larger than the SMA sibling, offering lower thermal resistance for the same die — the junction-to-ambient thermal impedance benefits from the wider copper pad area on the cathode tab. The wide Tj range means the leakage current at 85°C ambient stays within the datasheet limits — no derating concern for most general-purpose protection circuits.