Obsolete — sourcing reality for the 0451004.MR
Littelfuse has marked the 0451004.MR as obsolete. Availability is lot-specific; quantities and traceability are confirmed at the time of an RFQ.
4 A fast-blow — what the ratings mean for the board
Rated 4 A continuous at 125 V AC or DC, this is a fast-blow fuse — it clears on sustained overcurrents faster than a time-delay type, which matters when the downstream circuit has no significant inrush or start-up surge. The 50 A interrupting rating at rated voltage means it safely opens a fault up to that prospective current without rupturing the package. The melting I²t is 3.152, a figure that governs how much energy the fuse passes before it opens. A downstream semiconductor with a lower I²t withstand rating may fail before the fuse clears — this is the key co-ordination number for the protection engineer.
Housed in a 2-SMD square end block package measuring 6.10 mm x 2.69 mm x 2.69 mm, the 0451004.MR is a surface-mount device intended for reflow assembly.
Approvals and compliance
The 0451004.MR carries CSA, PSE, and UL approvals — accepted in North American and Japanese regulatory jurisdictions without additional testing.