Active production, 3.5 A fast-blow in a 2-SMD square-end block
The Littelfuse 045103.5MRL is an active-production NANO² 451 series surface-mount fuse rated 3.5 A at 125 V AC and 125 V DC, with a fast-blow response time. It comes in a 2-SMD square end block package measuring 6.10 mm x 2.69 mm x 2.69 mm, making it a drop-in fit for high-density board layouts where space is tight.
Breaking capacity is 50 A at the rated voltage — this fuse safely interrupts a fault current up to 50 A without rupturing or arcing, which is adequate for most secondary-side DC rails and low-power AC circuits. Melting I²t is 2.469 A²s, a measure of the energy needed to open the fuse element; a lower I²t means faster clearing under surge conditions, reducing stress on downstream components.
Approvals and temperature range
The fuse carries CSA, PSE, and UL approvals, meaning it is accepted in North American and Japanese regulatory jurisdictions without additional component-level testing.