Active production — 1 A fast-blow SMD fuse for board-level protection
The Littelfuse 0451001.MRSN is an active-production NANO²® 451 series surface-mount fuse rated 1 A at 125 V AC and 125 V DC, with a fast-blow response time. It clears faults up to 50 A at rated voltage, which covers most secondary-side protection scenarios in DC power rails and AC control circuits. The 2-SMD square end block package (6.10 mm x 2.69 mm x 2.69 mm) fits standard reflow assembly processes and occupies minimal board area, making it suitable for dense PCB layouts in power distribution, telecom, and industrial control modules.
Breaking capacity and I²t coordination
With a breaking capacity of 50 A at 125 V AC/DC, this fuse safely interrupts fault currents up to that level without rupturing the package — critical for ensuring the downstream PCB trace or component does not see sustained overcurrent. The 0.459 melting I²t value lets you calculate whether the fuse holds during capacitor inrush or motor start transients; a lower I²t means faster opening under surge conditions.
Thermal range and approvals
CSA and UR approval marks confirm acceptance for North American and Canadian equipment listings per UL 248-14 and CSA C22.2 No. 248.14.