The LM5072 Powered Device (PD) interface and Pulse-
Width-Modulation (PWM) controller provides a complete power
solution, fully compliant to IEEE 802.3af, for the PD
connecting into Power over Ethernet (PoE) networks. This
controller integrates all functions necessary to implement
both a PD powered interface and DC-DC converter with a
minimum number of external components. The LM5072 provides
the flexibility for the PD to also accept power from
auxiliary sources such as AC adapters in a variety of configurations.
The low RDS(ON) PD interface hot swap MOSFET
and programmable DC current limit extend the range of
LM5072 applications up to twice the power level of 802.3af
compliant PD devices. The 100V maximum voltage rating
simplifies selection of the transient voltage suppressor that
protects the PD from network transients. The LM5072 includes
an easy-to-use PWM controller that facilitates the
various single-ended power supply topologies including the
flyback, forward and buck. The PWM control scheme is based
on peak current mode control, which provides inherent advantages
including line feed-forward, cycle-by-cycle current
limit, and simplified feedback loop compensation. Two versions
of the LM5072 provide either an 80% maximum duty
cycle (-80 suffix), or a 50% maximum duty cycle (-50 suffix).