LM5071,pdf datasheet (Power Ov

The LM5071 power interface port and pulse width modulation
(PWM) controller provides a complete integrated solution
for Powered Devices (PD) that connect into Power over
Ethernet (PoE) systems. The LM5071 is specifically designed
for the PD that must accept power from auxiliary
sources such as ac adapters. The auxiliary power interface
of the LM5071 activates the PWM controller when the
ac adapter is connected to power the PD when PoE network
power is unavailable. The LM5071 integrates an 80V,
400mA line connection switch and associated control for a
fully IEEE 802.3af compliant interface with a full featured
current mode pulse width modulator dc-dc converter. All
power sequencing requirements between the controller interface
and switch mode power supply (SMPS) are integrated
into the IC.