200 mA fast-blow SMD fuse for secondary-side protection
The 0451.200MRSN is a Littelfuse NANO²® 451 series surface-mount fuse rated 200 mA at 125 VAC, with a 50 A interrupting capacity at rated voltage. Fast-blow response time means it clears quickly on moderate overcurrents — suited for protecting semiconductor circuits where the fault energy must be limited before the junction overheats.
Breaking capacity and cold resistance
Breaking capacity of 50 A at 125 VAC covers most secondary-side fault scenarios in control and instrumentation supplies — the fuse can interrupt a short-circuit current up to that level without rupturing. DC cold resistance is 0.8372 Ohms, which at 200 mA produces about 33 mW of self-heating — negligible for the 2-SMD square end block package in still air. Melting I²t of 0.0089 A²s gives a fast energy let-through; useful when the downstream silicon's surge rating is tight.
Temperature range and approvals
Approved by CSA and UR (UL Recognized) — accepted in North American and Canadian equipment listings without additional agency testing.