What the ratings mean on the bench
The 0603L035ZR is a Littelfuse POLY-FUSE® polymeric PTC resettable fuse in a 0603 surface-mount package, rated for a hold current of 350 mA and a trip current of 750 mA at 25°C. At 6V max and 40A max fault current, it protects low-voltage rails — think USB VBUS, battery outputs, or peripheral power — where a short pulls the line below the supply's current limit. The 100 ms trip time at 25°C means the PTC heats and latches high-resistance fast enough to keep the downstream silicon below its I²t damage threshold in most 6V bus faults. Post-trip resistance rises to 1 ohm max, so after the fault clears and the part cools, the residual voltage drop at 350 mA is under 350 mV — the load sees a clean restart.
Approvals include cURus and TUV, so the part carries recognized safety marks for equipment destined for North American and European markets.