3 A hold, 9 V max — the resettable overcurrent guard for tight board spaces
The Littelfuse 0603L300/9SLYR is a polymeric PTC resettable fuse from the POLY-FUSE® LoRho series, designed to protect low-voltage circuits up to 9 V from overcurrent faults. Its 3 A hold current (Ih) means it passes normal load current up to that level without tripping, while the 6 A trip current (It) defines the threshold where the device switches to a high-resistance state within 1 second (typical time to trip). Rated for a maximum fault current of 50 A, this PTC can safely interrupt short circuits without rupturing, making it suitable for USB port protection, battery pack overcurrent, and general-purpose board-level fault isolation in compact designs.
Resistance profile and temperature envelope
Initial resistance (Ri) is a minimum of 3 mOhms, and post-trip resistance (R1) rises to a maximum of 30 mOhms — the low Ri keeps I²R losses minimal during normal operation, while the post-trip state provides enough impedance to limit fault current to safe levels. The operating temperature range spans -40°C to +85°C, covering typical industrial and consumer environments.
Sourcing and compliance
It carries cURus and TUV approvals, confirming safety certification for North American and European markets. No stock-holding claim; each lot is verified for authenticity and RoHS compliance per the manufacturer's documentation.