Board-level protection for 20 A rails
The 0451020.MRL is a 20 A fast-blow surface-mount fuse from the Littelfuse NANO² 451 series, designed for overcurrent protection on high-current board-level power rails. Its 65 V AC/DC rating covers common 48 V telecom and 24 V industrial buses with headroom. Breaking capacity of 100 A AC and 150 A DC at rated voltage means the fuse safely interrupts fault currents up to those levels without rupturing — critical for DC bus protection where arcs sustain longer than AC zero-crossings. Fast-blow response clears overcurrents quickly, suited for circuits without large inrush loads. The 154 A²s melting I²t helps coordinate with downstream semiconductors so the fuse opens before the trace or FET does.
Package and thermal budget
Housed in a 2-SMD square end block package measuring 6.10 mm x 2.69 mm x 2.69 mm, the 0451020.MRL fits standard pick-and-place assembly. The 0.00244 Ω cold resistance at 20 A produces about 1 W self-heating at rated current — account for derating per the series curve in the datasheet when ambient exceeds 25 °C.
Sourcing and lifecycle posture
Available on tape and reel or cut tape for prototyping.