What the 1.5 A hold current means for your load budget
The Littelfuse 0603L150SLYR is a POLY-FUSE LoRho series polymeric PTC resettable fuse that protects low-voltage DC circuits up to 6 V. Its 1.5 A hold current (Ih) is the maximum steady-state current the fuse passes without tripping — below this threshold the PTC element stays in its low-resistance crystalline state.
Trip threshold and fault response
The 3 A trip current (It) is the minimum fault current that forces the PTC into its high-resistance state within 500 ms at 25°C. A short-circuit pulling 8 A will trip this device in the rated 500 ms, while a marginal 2.8 A overload may take several seconds or never trip — the trip time curve is non-linear and slows near the threshold. After tripping, the fuse latches in a high-resistance state (80 mOhms max post-trip), limiting the fault current to a few hundred milliamps. The 50 A maximum interrupt rating means the device can withstand a direct short on a 6 V supply capable of delivering 50 A without rupturing or catching fire. The initial resistance of 7 mOhms minimum keeps I²R losses under 16 mW at 1.5 A — negligible for a 0603 package but important to derate for ambient temperature above 25°C.