Obsolete — last-time-buy sourcing for BOM continuity
Littelfuse lists the 045103.5MR as Obsolete.
3.5 A fast-blow — what the ratings mean for fit
Rated 3.5 A continuous at 125 VAC or 125 VDC. The fast-blow response means it clears on sustained overcurrents faster than a time-delay fuse — suited for circuits where inrush is minimal and the protected load does not draw a start-up surge. Breaking capacity is 50 A at rated voltage — this is the maximum fault current the fuse can safely interrupt without rupturing. In a 125 V rail with a prospective short-circuit current above 50 A, the fuse may not clear the fault; upstream coordination or a higher-interrupting device is needed. Melting I²t is 2.469 — the energy let-through before the element opens. This number drives the downstream component sizing: a semiconductor or PCB trace must survive the I²t pulse without damage.
SMD package and temperature grade
Housed in a 2-SMD square end block package, 6.10 mm x 2.69 mm x 2.69 mm, surface-mount. The compact footprint fits dense PCB layouts where a through-hole cartridge fuse would consume too much real estate. Supplied on Tape & Reel — pick-and-place ready for automated assembly.
Approvals and compliance
Approved by CSA, PSE, and UL — the fuse carries acceptance for North American (CSA, UL) and Japanese (PSE) markets.