The LMR33640 incorporates an undervoltage-lockout feature on the output of the internal LDO (at the VCC pin). When VCC reaches about 3.7 V, the device is ready to receive an EN signal and start up. When VCC falls below approximately 3 V, the device shuts down, regardless of EN status. Since the LDO is in dropout during these transitions, the above values roughly represent the input voltage levels during the transitions.

Thermal shutdown is provided to protect the regulator from excessive junction temperature. When the junction temperature reaches about 165°C, the device shuts down; re-start occurs when the temperature falls to about 148°C .