Active production, 3.5 A fast-blow fuse for 125 V rails
The Littelfuse 045103.5NRL is an active-production surface-mount fuse from the NANO² 451 series, rated 3.5 A at 125 V AC and DC. It clears quickly on high overcurrents (fast-blow response), making it a fit for protecting downstream semiconductors, DC-DC converter input stages, and low-voltage power distribution in industrial control and telecom equipment.
Breaking capacity and temperature envelope
The interrupting rating is 50 A at the rated 125 V — the maximum fault current the fuse can safely clear. For circuits with available fault current above 50 A at 125 V, an upstream current-limiting device or a higher-interrupt fuse is needed. DC cold resistance is 0.02 ohms, which at 3.5 A translates to roughly 0.25 W of self-heating at rated current — negligible for most PCB layouts, but worth noting in high-density designs where adjacent components limit airflow.
Package and approvals
Housed in a 2-SMD, square end block package measuring 6.10 mm x 2.69 mm x 2.69 mm — compatible with standard 2410 (metric 6125) pad layouts. Approvals from CSA, PSE, and UL cover North American and Japanese regulatory acceptance, simplifying BOM compliance for equipment sold into those markets.