The LM6x4xx uses VCC as its internal power supply. VCC is, in turn, powered from VIN or BIAS. Once the LM6x4xx is active, power comes from VIN if BIAS is less than approximately 3.1 V. Power comes from BIAS if BIAS is more than 3.1 V. VCC is typically 3 V to 3.3 V under most conditions, but can be lower if VIN is very low. To prevent unsafe operation, VCC has a UVLO that prevents switching if the internal voltage is too low. See V_{CC_UVLO} and V_{CC_UVLO_HYST} in Section 7.5. During start-up, VCC momentarily exceeds its normal operating voltage until V_{CC_UVLO} is exceeded, then drops to its normal operating voltage. These UVLO values, when combined with the dropout of the LDO when only powering the LM6x4xx, are used to derive minimum V_{IN_OPERATE} and V_{IN_OP_H}.