8 A fast-blow in a 2-SMD footprint
The Littelfuse 0451008.NR is an 8 A fast-blow surface-mount fuse from the NANO² 451 series, rated for 125 V AC and DC. It clears a fault in under a millisecond on a dead short — the fast-blow characteristic means it opens before downstream silicon can secondary-fail, which is the main reason to pick it over a slow-blow in a board-mount position. Breaking capacity is 50 A at the rated voltage — enough for most secondary-side DC rails and low-power AC circuits where the available fault current stays under that ceiling. The 20.23 A²s melting I²t gives the coordination engineer a number to check against the upstream protection device's let-through energy.
Approvals and temperature envelope
The 0451008.NR carries CSA, cURus, and PSE approvals — accepted in North American and Japanese equipment without a separate agency review.