LM317A Thermal Shutdown Threshold

The LM317A regulators have internal thermal shutdown to protect the device from over-heating. Under all operating conditions, the junction temperature of the LM317A should not exceed the rated maximum junction temperature (TJ) of 125°C. Although the part can still operate passed this temperature, we do not recommend or guarantee the performance above that temperature. There is hysteresis on the order of a few degrees Celsius but this is not a spec we measure or guarantee for each part. There are many factors that affect the thermal shutdown such as layout, heat sinking, ambient temperature, if there is air flow, etc. These variations make a precise thermal threshold and hysteresis tough to spec in every case.