The internal thermal shutdown protection circuit disables the output when the thermal T_J of the pass transistor reaches the thermal T_{SD(shutdown) (typical)} threshold. T_J is the junction temperature and T_{SD(shutdown) (typical)} is the thermal shutdown temperature. The thermal shutdown circuit hysteresis verifies the LDO resets (turns on) when the temperature falls to T_{SD(reset) (typical)}.

The thermal time-constant of the semiconductor die is fairly short. Thus the device cycles on and off when thermal shutdown is reached until power dissipation is reduced. Power dissipation during start-up is high from large V_IN – V_OUT voltage drops across the device or from high inrush currents charging large output capacitors. Under some conditions, the thermal shutdown protection disables the device before start-up completes.

For reliable operation, limit the junction temperature to the maximum listed in the Recommended Operating Conditions table. Operation above this maximum temperature causes the device to exceed operational specifications. Although the device internal protection circuitry is designed to protect against thermal overload conditions, this circuitry is not intended to replace proper heat sinking. Continuously running the device into thermal shutdown or above the maximum recommended junction temperature reduces long-term reliability.