3.5 A fast-blow in 0603 — what the ratings mean for the BOM
The Littelfuse 046703.5NRHF is a Series 467 fast-blow chip fuse rated 3.5 A at 32 V AC/DC, with a 35 A interrupting rating at rated voltage. The 35 A breaking capacity means it safely clears a short-circuit fault up to that current without rupturing the package — a critical fit check when the available fault current at the board's input rail exceeds the fuse's interrupt rating. The 0.4306 melting I²t is the energy required to open the element. For a 3.5 A fast-blow fuse in a 0603 package, that I²t is low enough to protect a semiconductor input stage from a sustained overload, but high enough to ride through the inrush of a 100 µF input capacitor without nuisance opening — the same I²t number is the one the designer compares against the capacitor's surge energy.
0603 SMF footprint and board-level integration
The 0.0139 Ohm DC cold resistance at 3.5 A produces a voltage drop of about 49 mV and a power dissipation of roughly 170 mW — negligible in most circuits, but worth checking against the board's copper pour for ambient temperatures above 85 °C. The tape-and-reel packaging supports pick-and-place assembly with no manual handling step. The -55 °C to 90 °C operating range covers standard commercial and industrial enclosures; the upper limit of 90 °C means the fuse should not be placed near a hot regulator or power stage without thermal margin.
Approvals and compliance for regulatory acceptance
Carries CSA and UR recognition — the UR mark means UL 248-14 listing for supplementary protectors, which is the standard for board-level fuses not intended as branch-circuit protection. This approval set covers North American and Canadian regulatory acceptance for the end equipment.