What the voltage ratings mean for a TVS selection
The 1N6277ARL4G: For a 24 V rail with transients, that 15.3 V standoff gives roughly 9 V of headroom before the device turns on — enough to keep the line unclamped under normal switching while snapping shut on a surge. The clamping voltage at 25.2 V is the number that sizes the downstream IC's abs-max margin.
Temperature grade and the 175°C junction ceiling
Rated from -65°C to 175°C junction temperature — that range puts the Mosorb™ series in industrial and automotive-adjacent environments rather than consumer electronics. A 175°C TJ ceiling with a typical board-level thermal resistance on a DO-201AD gives real headroom in enclosed panels or under-hood instrument clusters where ambient can spike. The lead solder joint and the axial lead thermal resistance are the limiting path to the ambient; a long lead length into a heat-sinking plane can drop the effective TJ significantly below the 175°C rating at full pulse.
Sourcing reality — obsolete with no named successor
There is no cross-reference to a pin-compatible replacement in the current Mosorb™ line. For a new design this means a parametric re-evaluation against the current Littelfuse TPSMB or 1.5KE series is required before committing to the BOM — the board footprint may be reusable if the DO-201AD package is retained, but the exact clamping characteristics need verification against the current datasheet revision.