4 A fast-blow with 50 A interrupting capacity
The 0451004.MRSN is a 4 A, 125 VAC fast-blow fuse from the Littelfuse NANO²® 451 series, designed for surface-mount board-level protection. Its 50 A breaking capacity at rated voltage means it can safely interrupt a fault current up to that level without rupturing the package — a critical parameter for secondary-side protection in power supplies where the prospective short-circuit current stays below 50 A.
Melting I²t and inrush tolerance
With a melting I²t of 3.152, this fuse can tolerate brief current surges — such as capacitor charging inrush or motor start spikes — without nuisance opening. The 0.016 Ohm DC cold resistance keeps voltage drop low in the steady state, minimising I²R heating in the circuit path.
The 2-SMD square end block package (6.10 mm x 2.69 mm x 2.69 mm) fits standard pick-and-place assembly and reflow profiles.