400 mA fast-blow SMD fuse — NANO²® 451 series
The Littelfuse 0451.400NRL is a 400 mA fast-blow surface-mount fuse from the NANO²® 451 series, designed to protect sensitive circuits where a quick open on overcurrent prevents damage to downstream silicon or trace work. Rated for 125 V AC and DC with a 50 A interrupting capacity at that voltage, it clears faults within its rating without rupturing the package — a key constraint when the available fault current from the supply exceeds the fuse's breaking capacity.
Melting I²t and coordination
The 0.0484 melting I²t value lets a designer verify that downstream components — like a regulator or FET — can survive the energy let-through before the fuse opens.
Housed in a 2-SMD square end block package measuring 6.10 mm x 2.69 mm x 2.69 mm, the 0451.400NRL sits flat on the board for reflow soldering and mates with standard pick-and-place equipment.
Compliance and approvals
Carries CSA and UL approvals, confirming the fuse meets North American safety standards for overcurrent protection in equipment.