1.5 A fast-blow SMD fuse for board-level overcurrent protection
The Littelfuse 045101.5MRL is a 1.5 A, 125 V AC/DC fast-blow SMD fuse from the NANO²® 451 series, housed in a 2-SMD square end block package measuring 6.10 mm x 2.69 mm x 2.69 mm. It protects sensitive circuits on the board where a cartridge-style fuse won't fit — think power inputs on industrial controls, telecom line cards, or battery-management modules that need a compact, surface-mount overcurrent interrupt.
Breaking capacity and inrush handling
Rated breaking capacity is 50 A at 125 V AC or DC — enough to clear a hard short on a low-impedance bus without the fuse body rupturing. The 0.853 melting I²t tells you how much energy the fuse absorbs before opening: a downstream capacitor bank or motor start that dumps more than 0.853 A²s will blow it on the first surge, so budget the inrush profile against this number. Cold resistance is 0.063 ohms, which at 1.5 A continuous drops about 95 mV and dissipates roughly 140 mW — negligible for most boards, but worth checking if the fuse sits in a tightly regulated 1.8 V rail where every millivolt counts. The fast-blow characteristic means it opens quickly on overcurrent but may nuisance-blow on repetitive inrush pulses that exceed the I²t rating.