A thermal shutdown protection circuit disables the LDO when the junction temperature (T_J ) of the pass transistor rises to T_SD(shutdown) (typical). Thermal shutdown hysteresis assures that the device 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 can cycle off and on when thermal shutdown is reached until power dissipation is reduced. Power dissipation during start up can be 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 can disable the device before start up completes. For reliable operation, limit the junction temperature to the maximum listed in the Electrical Characteristics table. Operation above this maximum temperature causes the device to exceed operational specifications. Although the internal protection circuitry of the device 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.