1.5 A fast-blow fuse for secondary-side protection
The Littelfuse 045101.5NR is a 1.5 A fast-blow surface-mount fuse from the NANO²® 451 series, rated for 125 V AC and 125 V DC circuits. The fast-blow response means it clears quickly on overcurrent — essential for protecting downstream semiconductors that cannot tolerate sustained fault current. With a breaking capacity of 50 A at the rated voltage, this fuse can safely interrupt fault currents up to that level without rupturing or arcing across the element. The 0.853 melting I²t figure helps coordination engineers size the upstream protection — the fuse element absorbs that energy before opening, so the upstream breaker or fuse sees the clearing event as a downstream fault.
Obsolete — sourcing through independent channels
Littelfuse lists the 045101.5NR as obsolete. No official successor order code is recorded, so the replacement path is not a direct pin-compatible drop-in from the same manufacturer. The part is available through independent surplus and broker channels; quantities and pricing are confirmed at RFQ time against the specific BOM line. For existing designs already qualified on the NANO²® 451 footprint, the 1.5 A rating, fast-blow characteristic, and 2-SMD Square End Block package are the parameters to match when evaluating a functional replacement. The 0.063 Ohm DC cold resistance gives a baseline for voltage drop at rated current — about 95 mV at 1.5 A.
Regulatory approvals and temperature range
The fuse carries CSA, PSE, and UL approvals — covering North American and Japanese regulatory acceptance for equipment-level safety certification.