Polymeric PTC, 1 A hold, 6 V max
The Littelfuse 1206L100WR is a surface-mount polymeric PTC resettable fuse from the POLY-FUSE 1206L series. It holds 1 A continuous current at 6 V max and trips to a high-resistance state under fault, protecting downstream circuitry without a fuse replacement. Rated for a maximum interrupt current of 100 A, it clears hard shorts on low-voltage rails where the available fault current is high. The 300 ms typical time-to-trip means the PTC transitions fast enough to limit energy let-through into the load.
Package and rework reality
The concave termination profile leaves the end caps visible for inspection and rework — a hot-air station lifts this part cleanly without lifting the pad, provided the board is preheated to 100 °C to reduce thermal shock on the ceramic substrate. Initial resistance is 55 mOhms minimum; post-trip resistance rises to 210 mOhms maximum. That post-trip ceiling sets the voltage drop the circuit sees after a fault clears — at 1 A the drop is 210 mV, well within a 3.3 V rail's tolerance but worth noting on a 1.8 V rail where every millivolt counts. The hold current derates at the temperature extremes — at 85 °C the 1 A rating drops to roughly 70 % of the 25 °C value, so a design pulling 700 mA continuous at the hot end still has margin.
Obsolete — sourcing path
Marked obsolete by Littelfuse. For a BOM already qualified to this footprint and hold current, the 1206L100WR remains a viable replacement source while surplus inventory lasts. A design-in for new production should evaluate the current POLY-FUSE 1206L active portfolio for a drop-in parametric match.