The internal thermal shutdown protection circuit disables the output when the thermal junction temperature (T_J ) of the pass transistor rises to the thermal shutdown temperature threshold, T_SD(shutdown) (typical). The thermal shutdown circuit hysteresis makes sure that 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 can cycle on and off when thermal shutdown is reached until the 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 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 internal protection circuitry is designed to protect against thermal overload conditions, this circuitry is not intended to replace proper heat sinking. Continuously running the regulator into thermal shutdown or above the maximum recommended junction temperature reduces long-term reliability.