PTC resettable fuse for low-voltage rail protection
The Littelfuse 1206L110SLYR is a polymeric PTC resettable fuse from the POLY-FUSE® LoRho series, designed to protect low-voltage DC power rails against overcurrent faults. With a 1.1 A hold current and a 6 V maximum voltage rating, it sits in the 1206 surface-mount footprint — a common choice for USB ports, battery packs, and portable electronics where resettable protection eliminates fuse replacement.
Hold current, trip current, and what they mean for your circuit
The 1.1 A hold current (Ih) is the maximum steady-state current the device passes without tripping at 25 °C ambient. Above that, the 2.2 A trip current (It) defines the threshold where the PTC resistance rises sharply — the part switches from a low-resistance state (15 mOhms initial, Ri min) to a high-resistance state (100 mOhms post-trip, R1 max), limiting current to a leakage level. Time to trip is 300 ms at the rated fault condition — fast enough to protect downstream components from sustained overcurrent without nuisance tripping on inrush spikes. The 50 A maximum fault current rating means the device can interrupt short circuits up to that level without rupturing, provided the supply voltage stays at or below 6 V.
The concave termination style improves solder fillet visibility during AOI.
Compliance and approvals
The part carries cURus and TUV agency approvals, indicating it has passed safety testing for overcurrent protection devices under UL 1434 and IEC 60738-1 standards. This simplifies acceptance in equipment destined for North American and European markets.