What the 4 A rating and 50 A breaking capacity mean for your board
The 1206SFP400F/32-2: Rated 4 A continuous at 32 V DC, this SFP-series fuse clears a fault up to 50 A at that voltage — the interrupting rating is the ceiling for the available fault current the fuse must safely open without arcing or rupturing the 1206 ceramic body. The cold resistance is 0.023 ohms, so at 4 A the I²R loss is under 0.4 W — negligible for the 1206 footprint, but the melting I²t of 2.74 A²s means the fuse tolerates inrush pulses (like a capacitor charge or motor start) up to that energy before the element opens.
Obsolete — how to source this fuse today
Sourced through independent surplus and broker channels.
Package, temperature range, and compliance
UL approved — the fuse carries the UL recognition mark, which certifies its interrupting rating and safe operation under the conditions listed in the UL standard for supplementary protectors.