R1540x-Y NO.EY-513-190411 THEORY OF OPERATION Thermal Shutdown Thermal Shutdown occurs when the device’s junction temperature reaches 165°C (Typ.) at which point the regulator will automatically shut down. Then the regulator resumes from the stand-by state when the junction temperature decreases below 135°C (Typ.). Unless the cause of overheating is eliminated, the device cycles on and off to generate pulse output. 9