Hold current and trip behaviour
The Littelfuse 0603L075SLYR is a polymeric PTC resettable fuse from the POLY-FUSE LoRho series, rated for a hold current (Ih) of 750 mA at 6 V max. When the fault current exceeds 1.5 A (It, the trip current), the device heats up and its resistance rises sharply, switching from a low-impedance path to a high-impedance state that limits the current to a leakage level. This trip event happens within 200 ms at 25 °C, fast enough to protect downstream circuitry from sustained overcurrents without a manual reset—once the fault clears and power cycles, the PTC cools and returns to its low-resistance state.
Package and footprint reality
The concave termination style suits automated pick-and-place and wave-solder processes, and the 0603 footprint means it fits standard pad layouts without a stencil change. Initial resistance (Ri) is 20 mOhms minimum; after a trip event, the post-trip resistance (R1) rises to 165 mOhms maximum. This low initial resistance keeps I²R losses minimal during normal operation—critical for battery-powered or high-density boards where every milliohm of series resistance eats into the voltage budget.
Environmental and compliance envelope
The 50 A maximum interrupt current rating means it can safely clear a short-circuit fault up to that level without rupturing or catching fire.