8 A fast-blow SMD fuse for secondary-side protection
The Littelfuse 0451008.MRL is an 8 A fast-blow fuse in the NANO²® 451 series, rated for 125 V AC and DC. It clears overcurrents quickly — the fast-blow characteristic means it opens within milliseconds on a hard short, protecting downstream semiconductors and PCB traces before they heat beyond their limits. With a breaking capacity of 50 A at rated voltage, it safely interrupts fault currents up to that level without rupturing or sustaining an arc. The 20.23 melting I²t figure tells you how much energy the fuse absorbs before opening — useful for sizing it against inrush from capacitive or light inductive loads so it doesn't nuisance-blow on start-up.
Package and process fit
Housed in a 2-SMD square end block package measuring 6.10 mm x 2.69 mm x 2.69 mm, this fuse sits flat on the pad for a stable solder joint. Surface-mount assembly means it runs through the same reflow profile as the rest of the board — no hand-soldering step. Supplied in tape and reel, it feeds directly into a pick-and-place machine without a feeder change.
Temperature range and approvals
Approvals from CSA, PSE, and UL mean it is accepted in North American and Japanese equipment — no extra agency review for those markets.