What the 1.5 A hold current means for your board
The 1206L150SLYR is a polymeric PTC resettable fuse from Littelfuse's POLY-FUSE LoRho series, rated for a 1.5 A hold current (Ih) at 25 °C. This is the continuous current the device passes without tripping — stay at or below it in normal operation. The trip current (It) is 3.9 A, meaning the device will start to switch to a high-resistance state when the fault current exceeds that threshold. With a maximum voltage rating of 6 V, this part is sized for low-voltage DC rails — think USB power, battery protection, or peripheral port outputs.
Trip time and resistance — the real-world behavior
Time to trip is 300 ms at 25 °C under fault conditions. That is fast enough to protect downstream silicon from overcurrent damage in most low-voltage applications, but slow enough to avoid nuisance tripping from inrush current spikes on capacitive loads. Initial resistance (Ri) is 10 mOhms minimum, and post-trip resistance (R1) rises to 65 mOhms maximum. The LoRho series is designed for lower resistance than standard PTCs — the 10 mOhm floor means less voltage drop and heat generation at the 1.5 A hold current, which matters when the fuse sits on a power rail feeding sensitive logic.
Package, footprint, and temperature range
The hold current derates at elevated temperatures — at 85 °C the 1.5 A rating drops to roughly 60-70% of the 25 °C value, so factor that into the thermal budget if the fuse sits near a hot regulator or in a sealed enclosure.