What the 6.3 A rating means for your board
The 045106.3MRL is a Littelfuse NANO²® 451 series surface-mount fuse rated 6.3 A continuous at 125 V AC or DC. The fast-blow response time means it clears on moderate overcurrents quickly — the element fuses before downstream traces or semiconductors reach their I²t limit. For a 6.3 A rail, the 0.0096 ohm DC cold resistance keeps voltage drop under 60 mV at full load, which matters for low-voltage supplies where every millivolt of headroom counts.
Breaking capacity and fault clearing
Rated breaking capacity is 50 A at the rated voltage. In a 125 V circuit, this fuse safely interrupts a fault current up to 50 A without rupturing the package or sustaining an arc. The melting I²t of 9.17 A²s is the energy needed to open the element — coordinate this with the I²t rating of the downstream components (traces, connectors, semiconductors) so the fuse clears before they fail.
Approvals and temperature envelope
At the high end, derate the continuous current per the manufacturer's curve (not reproduced here) to avoid nuisance opening from ambient heating.
Housed in a 2-SMD square end block package measuring 6.10 mm x 2.69 mm x 2.69 mm. Surface-mount assembly with tape-and-reel packaging (Cut Tape option also available) — the square end terminals provide good solder joint visibility for AOI. The compact footprint suits dense PCB layouts where a through-hole cartridge fuse would consume too much real estate.
Sourcing and lifecycle posture
Listed as Active in the manufacturer's lifecycle record. No end-of-life notice or successor part is on file. The NANO² 451 series is a mature, widely stocked line; no single-source risk flagged.