What the hold and trip ratings mean for your circuit
The 1206L012/48WR is a polymeric PTC resettable fuse from the POLY-FUSE 1206L series, rated for a hold current of 125 mA at 48 V max. At room temperature, the device will not trip below 125 mA continuous; once the fault current exceeds the trip current of 290 mA, the polymer heats up and the resistance jumps from a minimum of 1.5 ohms to a maximum of 6 ohms within 200 ms, effectively limiting the current to a low level. The 10 A max current rating is the fault current the part can withstand without damage during the trip event — it is not a continuous rating. For a 125 mA nominal load, a short-circuit current of up to 10 A at 48 V will be safely interrupted, and the fuse resets when power is removed and the polymer cools.
The concave termination style provides a visible solder fillet on the side of the package, aiding inspection. Operating temperature range is -40°C to 85°C, which covers most indoor and outdoor telecom, industrial, and automotive cabin environments. The hold current derates with temperature — at 85°C the effective hold current is lower than the 25°C rating, so the circuit designer must apply the manufacturer's derating curve.
Approvals and compliance
The 1206L012/48WR carries cURus and TUV approvals, confirming it meets North American and European safety standards for overcurrent protection components. These marks are required for equipment sold into those regulated markets.