Active production and BOM-fit baseline
The Littelfuse 1206L050/15YR is an active-production polymeric PTC resettable fuse in the POLY-FUSE® 1206L series, rated for a hold current of 500 mA at 15 V max. This means it passes normal circuit current up to half an amp and trips when the fault current exceeds 1 A, resetting after the overcurrent condition clears and power is removed. With a maximum fault current rating of 100 A, it safely interrupts high-energy shorts without rupturing, provided the supply impedance keeps the prospective short-circuit current below that ceiling. The 100 ms typical time-to-trip at 8 A (from the series characteristic) means fast-acting protection for downstream silicon.
Resistance states and thermal budget
Initial resistance is a minimum of 150 mOhms; after tripping and cooling, the post-trip resistance rises to a maximum of 750 mOhms. The ratio between these two states — roughly 5× — is typical for a polymeric PTC and means the series resistance in the circuit path changes after a fault event, which can affect low-voltage rail regulation if the PTC is in the feedback path. Derate the hold current above 25°C per the POLY-FUSE 1206L curve — at 85°C ambient the effective hold current drops to roughly 60% of the 25°C rating, so a 500 mA nominal part may only carry 300 mA reliably in a hot enclosure.
Footprint and approvals
The concave termination profile suits standard reflow soldering and allows visual inspection of the solder joint fillet. Surface-mount pick-and-place compatible. Approved by cURus and TUV, covering North American and European safety agency requirements for overcurrent protection components. The approvals certify the part meets UL 1434 and IEC 60738-1 standards for polymeric PTCs.