LM5072 Datasheet, PDF (1/24 Pages) National Semiconductor (TI) – Integrated 100V Power Over Ethernet PD Interface and PWM Controller with Aux Support

March 2006
LM5072
Integrated 100V Power Over Ethernet PD Interface and
PWM Controller with Aux Support
General Description
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 pro-
vides the flexibility for the PD to also accept power from
auxiliary sources such as AC adapters in a variety of con-
figurations. The low RDS(ON) PD interface hot swap MOS-
FET 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 in-
cludes 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 inher-
ent advantages including line feed-forward, cycle-by-cycle
current limit, and simplified feedback loop compensation.
Two versions of the LM5072 provide either an 80% maxi-
mum duty cycle (-80 suffix), or a 50% maximum duty cycle
(-50 suffix).
Features
PD Interface
n Fully Compliant IEEE 802.3af PD Interface
n Versatile Auxiliary Power Options
n 9V Minimum Auxiliary Power Operating Range
n 100V Maximum Input Voltage Rating
n Programmable DC Current Limit Up To 800mA
n 100V, 0.7Ω Hot Swap MOSFET
n Integrated PD Signature Resistor
n Integrated PoE Input UVLO
n Programmable Inrush Current Limit
n PD Classification Capability
n Power Good Indicator
n Thermal Shutdown Protection
PWM Controller
n Current Mode PWM Controller
n 100V Start-up Regulator
n Error Amplifier with 2% Voltage Reference
n Supports Isolated and Non-Isolated Applications
n Programmable Oscillator Frequency
n Programmable Soft-Start
n 800 mA Peak Gate Driver
n 80% Maximum Duty Cycle with Built-in Slope
Compensation (-80 device)
n 50% Maximum Duty Cycle, No Slope Compensation
(-50 device)
Applications
n IEEE 802.3af Compliant PoE Powered Devices
n Non-Compliant, Application Specific Devices
n Higher Power Ethernet Powered Devices
Packages
n TSSOP-16 EP (Exposed Pad)
Simplified Application Diagram
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