100 mA fast-blow protection in a 2-SMD footprint
The Littelfuse 0451.100MRSN is a 100 mA fast-blow surface-mount fuse from the NANO²® 451 series, rated for 125 VAC with a 50 A interrupting capacity at that voltage. The 0.00138 melting I²t means it clears fast on a dead short but holds through moderate inrush — a 100 mA rail that sees a brief capacitor charge will stay up.
Package and board-fit constraints
Housed in a 2-SMD square end block measuring 6.10 mm x 2.69 mm x 2.69 mm, this fuse sits flat on the board with no through-hole leads — the pad layout is the same as the standard NANO² footprint. Supplied on Tape & Reel, it feeds straight into a pick-and-place machine; the 3.1 Ohm DC cold resistance means the voltage drop at rated current is about 0.31 V, negligible for a 125 V rail.
Temperature range and approvals
Carries CSA and UR approvals, so it is accepted in North American and Canadian equipment without a separate component-level evaluation.