Ratings: what the 315 mA and 50 A breaking capacity mean for the board
The 0451.315MR: Rated 315 mA at 125 VAC and 125 VDC, this is a fast-blow fuse — it clears quickly on overcurrent, protecting sensitive downstream components. The 50 A interrupting rating at rated voltage means it safely opens the circuit under a fault up to that current without rupturing or arcing across the package. In a 125 VDC rail, a short-circuit current below 50 A is within the fuse's safe clearing envelope.
Package and board-fit: 2-SMD square end block, 6.10 mm length
Housed in a 2-SMD square end block package, measuring 0.240" x 0.106" x 0.106" (6.10 mm x 2.69 mm x 2.69 mm). The surface-mount footprint suits high-density PCB layouts where a through-hole cartridge fuse would consume too much board area. The 0.3918 Ohms DC cold resistance is the steady-state resistance before a fault — useful for estimating voltage drop at the rated 315 mA load (0.124 V drop at rated current).
Approvals and temperature range
CSA and UL approved — the fuse carries North American safety agency marks, which simplifies acceptance in UL-listed equipment.