ISL6719 pdf datasheet (100V Li

The ISL6719 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 provides a single adjustable output rated at 100mA from either the input source or an auxiliary source such as a transformer winding. The auxiliary source is selected whenever it has sufficient voltage to sustain the output.
The ISL6719 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 100mA from a 100V source for short
durations. This period of time allows the power supply to start-up and provide an alternate power source, such as the output of a transformer winding, to the AUXIN input. This allows the regulated output to operate from a lower source voltage to minimize power loss.