3 A fast-blow SMD fuse for secondary-side protection
The Littelfuse 0451003.MRSN is a 3 A, 125 VAC rated fast-blow fuse in the NANO²® 451 series, housed in a 2-SMD square end block package. It is a board-mount fuse (cartridge style excluded) designed for surface-mount assembly on densely populated PCBs where a low-profile, high-reliability overcurrent protection element is needed. With a DC cold resistance of 0.0227 Ohms and a melting I²t of 1.65, this fuse provides predictable, repeatable clearing characteristics for protecting downstream semiconductors and power rails from short-circuit faults. The 50 A breaking capacity at 125 VAC means it can safely interrupt a fault current up to that level without rupturing or sustaining an arc.
Package, approvals, and temperature range
Its compact footprint — 0.240" L x 0.106" W x 0.106" H (6.10 mm x 2.69 mm x 2.69 mm) — fits tight board layouts where space is at a premium. Safety approvals from CSA, METI, and UR confirm the fuse meets recognized standards for overcurrent protection in equipment destined for North American and Asian markets.
Active production — sourcing posture
It is a current-production part, sourced through authorized and independent distribution channels. Pricing and lead time are confirmed at quote against the BOM quantity.