What the 2 A rating means for your board
The 0451002.MR is a 2 A fast-blow SMD fuse from the Littelfuse NANO²® 451 series, rated for 125 V AC and 125 V DC. The 2 A current rating is the continuous current the fuse can carry without opening under normal conditions — it is the nominal rating, not a trip threshold. A sustained overload above 2 A will clear the fuse within the fast-blow response curve, which is specified by the melting I²t of 0.53 A²s. The 50 A breaking capacity at rated voltage means the fuse can safely interrupt a fault current up to 50 A without rupturing or sustaining an arc — critical for DC circuits where arcs are harder to extinguish.
Housed in a 2-SMD square end block package measuring 6.10 mm x 2.69 mm x 2.69 mm, this fuse is a surface-mount device intended for reflow soldering. The package footprint is compatible with standard pick-and-place equipment, and the tape-and-reel packaging (Cut Tape also available) supports volume assembly.
Lifecycle reality — obsolete, sourced to order
Littelfuse has marked the 0451002.MR as obsolete. This means the manufacturer no longer produces the part; any remaining inventory is in the distribution channel or surplus market.