Application Note : DCDC Converters (Switching Regulators)
To provide more stable operation some DCDC converters contain a UVLO (Undervoltage Lockout) function. After turning on power, the UVLO function keeps the internal circuits in the standby state until the DCDC converter input voltage (VIN) reaches the UVLO released voltage, it is to avoid malfunctioning of the product below the UVLO voltage.
In case the input voltage (VIN) drops below the UVLO detect voltage during operation, the UVLO function forces the DCDC converter into the standby state to prevent to a malfunctioning.
When the input voltage (VIN) rises above the UVLO released voltage again, the UVLO released the DCDC converter.