Board-level overcurrent protection for 1.6 A rails
The Littelfuse 045101.6MRL is a NANO² 451 series surface-mount fuse rated 1.6 A at 125 VAC and 125 VDC, fast-blow response. It protects a 1.6 A load circuit — think a 24 VDC sensor bank, a 5 V logic rail, or a 12 V auxiliary supply on a control board — where the fuse must clear before the downstream regulator or connector exceeds its thermal limit. The 50 A breaking capacity at rated voltage means it safely interrupts a fault current up to that level without rupturing the package or sustaining an arc — sufficient for most secondary-side DC rails and low-power AC branch circuits where the prospective short-circuit current stays under 50 A.
What the ratings mean for the BOM line
The 1.6 A current rating is the continuous current the fuse carries at 25°C ambient without opening. For a 1.6 A load, the fuse operates below its nominal rating with margin; for a 1.5 A load, it sits at 94% of rating — within the typical derating guideline of 75-80% for elevated ambient. The fast-blow characteristic means it opens quickly on a moderate overcurrent, protecting semiconductor junctions that cannot tolerate sustained overload. Melting I²t of 1.06 A²s is the energy required to melt the fuse element. This number governs inrush withstand: a capacitor bank charging through this fuse must stay below 1.06 A²s total energy, or the fuse opens on start-up. It also coordinates with downstream semiconductor fuses or PTCs — the 045101.6MRL should clear before a 2 A fast-blow in series, given the I²t ratio. DC cold resistance of 0.058 Ohms at 25°C produces a voltage drop of 93 mV at rated current — negligible for a 5 V or 12 V rail, but worth checking if the load is a 1.6 A, 1.8 V FPGA core where every millivolt of IR drop matters.
The 2-SMD square end block package measures 6.10 mm long by 2.69 mm wide and 2.69 mm tall — a compact footprint for dense PCB layouts. The square end terminals are soldered to pads on both ends; the fuse body sits above the board, so the solder fillet is visible for AOI inspection. Supplied in Tape & Reel (TR) or Cut Tape (CT) — the TR option suits automated pick-and-place for volume production; CT works for prototype or low-volume builds.
Compliance and sourcing posture
The 045101.6MRL carries CSA, PSE, and UL approvals — accepted in North American, Japanese, and many international regulatory frameworks. UL recognition means the fuse is listed to UL 248-14, the standard for supplementary fuses used in equipment not intended for branch-circuit protection.