Thermal shutdown disables the output when the junction temperature T_J rises to the shutdown temperature threshold T_SD. The thermal shutdown circuit hysteresis requires the temperature to fall to a lower temperature before turning on again. The thermal time constant of the semiconductor die is fairly short; thus, the device may cycle on and off 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 disables the device before start up completes.

For reliable operation, limit the junction temperature to the maximum listed in the Section 6.3 table. Operation above this maximum temperature causes the regulator to exceed operational specifications.

Although the thermal shutdown circuitry is designed to protect against temporary thermal overload conditions, this circuitry is not intended to replace proper thermal design. Continuously running the regulator into thermal shutdown or above the maximum recommended junction temperature reduces long-term reliability.