1.25 A fast blow — what the ratings mean for the board
The 04511.25MRSN: Rated 1.25 A at 125 VAC with a 50 A interrupting capacity — enough to clear a hard short on a secondary power rail without the package rupturing. The fast-blow response time means it opens quickly on overcurrent, protecting downstream silicon from prolonged fault energy. Melting I²t is 0.664 — this is the coordination figure for upstream PCB trace or a PTC resettable device. At 1.25 A the fuse opens fast enough that a 10 mil trace on standard copper survives a dead short without lifting the pad.
2-SMD square end block — rework and footprint
The end terminations are large enough to get a hot-air nozzle over without cooking the adjacent passives. Surface-mount package on Tape & Reel — pick-and-place ready, but the square end block also reworks cleanly with a standard hot-air profile. No hidden pads under the body.
Approvals and temperature range
CSA and UR approval means the fuse is accepted in North American and Canadian equipment without a separate UL-recognition chase.