8.1.6 Undervoltage Lockout (UVLO) Operation
The UVLO circuit ensures that the device stays disabled before its input supply reaches the minimum operational voltage range, and ensures that the device shuts down when the input supply collapses. See Figure 46 for rising and falling thresholds. Figure 51 depicts the UVLO circuit response to various input voltage events. The diagram can be separated into the following parts:
- Region A: The device does not start until the input reaches the UVLO rising threshold
- Region B: Normal operation, regulating device
- Region C: Brownout event above the UVLO falling threshold (UVLO rising threshold – UVLO hystersis). The output may fall out of regulation but the device is still enabled.
- Region D: Normal operation, regulating device
- Region E: Brownout event below the UVLO falling threshold. The device is disabled in most cases and the output falls as a result of the load and active discharge circuit. The device is re-enabled when the UVLO rising threshold is reached by the input voltage and a normal start-up follows.
- Region F: Normal operation followed by the input falling to the UVLO falling threshold
- Region G: The device is disabled as the input voltage falls below the UVLO falling threshold to 0 V. The output falls as a result of the load and active discharge circuit.
Figure 51. Typical UVLO Operation