0.5Amp is bit low.
Specs of fuse you need for Ds Dslite AND DSi
-FUSE, FAST ACTING, SMD, 1A
-Voltage Rating VDC:32V
-Fuse Current:1A
-Breaking Capacity:50A @ 32V DC
-Blow Characteristic:Fast Acting
-Fuse Case Style:0603
-SVHC:No SVHC (20-Jun-2011)
-Approval Bodies:UL, CSA
-Breaking Capacity Current DC:35A
-Colour Code:Brown
-External Length / Height:1.6mm
-External Width:0.8mm
-Fuse Breaking Capacity Voltage DC:24V
-Fuse Size Held:1.6mm x 0.81mm x 0.48mm
-Fuse Type Blowing Characteristic:Fast Acting
-Overall Height:0.48mm
-Overall Length:1.6mm
-Package / Case:0603
-Resistance @ 10% Rated Current Typ:0.15ohm
-SMD Fuse Case Style:0603
-Voltage Drop @ Rated Current:0.18V