What this 7A fast-blow NANO² fuse protects
The Littelfuse 0451007.NR is a 7 A fast-blow surface-mount fuse from the NANO²® 451 series, rated for 125 V AC and 125 V DC with a breaking capacity of 50 A at rated voltage. The 50 A interrupting rating means it can safely clear a fault current up to that level without rupturing the package — a critical spec for secondary-side protection in power supplies or DC bus lines where the available fault current stays under that ceiling.
Fast-blow response and I²t for inrush handling
The fast-blow characteristic paired with a melting I²t of 10.32 means this fuse opens quickly on sustained overloads but tolerates brief inrush pulses — useful when the protected circuit has a capacitive input filter or a motor start transient that lasts a few milliseconds. The 0.009 Ohm cold resistance keeps voltage drop under 63 mV at rated current, which matters for low-voltage rails where every millivolt of headroom counts.
Package, mounting and environmental range
Housed in a 2-SMD square end block package measuring 6.10 mm x 2.69 mm x 2.69 mm, this fuse sits flat on the board for a low-profile solder footprint. Surface-mount construction with Tape & Reel packaging feeds directly into pick-and-place lines.
Regulatory approvals and compliance documentation
Approved by CSA, PSE, and UL — the UL listing confirms it meets the standard for branch-circuit overcurrent protection in North America, while PSE opens the door for equipment destined for the Japanese market. These marks are the authority signals a compliance engineer needs for the safety cert package.
Sourcing an obsolete part — what to expect
Littelfuse lists the 0451007.NR as obsolete. For BOM lines that still call out this order code, supply runs through independent surplus and broker channels — each lot is date-code traceable, and the laser etch on the package should be inspected for font consistency against known Littelfuse plant markings. Availability and pricing are confirmed at RFQ time against the specific quantity needed.