The VIN UVLO circuit makes sure that the device remains disabled before the input supply reaches the minimum operational voltage range. The VIN UVLO circuit also makes sure that the device shuts down when the input supply collapses. Similarly, the VBIAS UVLO circuit makes sure that the device stays disabled before the bias supply reaches the minimum operational voltage range. The VBIAS UVLO circuit also makes sure that the device shuts down when the bias supply collapses.
Typical VIN or VBIAS UVLO Circuit Operation depicts the UVLO circuit response to various input or bias voltage events. The diagram can be separated into the following parts:
- Region A: The output remains off while either the input or bias voltage is
below the UVLO rising threshold.
- Region B: Normal operation, regulating device.
- Region C: Brownout event above the UVLO falling threshold (UVLO rising
threshold – UVLO hysteresis). The output can
possibly 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 reenabled when the UVLO rising threshold is
reached and a normal start up follows.
- Region F: Normal operation followed by the input or bias falling to the UVLO
falling threshold.
- Region G: The device is disabled when either the input or bias voltage falls below the UVLO falling threshold to 0 V. The output falls as a result of the load and active discharge circuit.