ISL6720/ISL6720A pdf datasheet

The ISL6720A is a low cost linear regulator for generating a
low voltage bias supply from intermediate distributed
voltages commonly used in telecom and datacom
applications. It produces three separate outputs, an
adjustable 0V to 20V output rated at up to 125mA which can
be back-biased from an external source such as an auxiliary
transformer winding, a 50mA switched regulated output
adjustable between 0V and 15V, and a fixed continuous 5V
output rated at 25mA.
The ISL6720A may be used as a start-up or a continuous
low power regulator. When operating as a start-up regulator,
it is capable of sourcing over 100mA from a 100V source for
short durations. This period of time allows the power supply
to start-up and provide a low voltage alternate power source,
such as the output of a transformer winding, to the VIO
output. This allows the remaining outputs to be operated
from a lower source voltage thereby minimizing power loss.