LM5071

Power Over Ethernet PD Controller with Auxiliary Power

Interface

General Description

The LM5071 power interface port and pulse width modula-

tion (PWM) controller provides a complete integrated solu-

tion for Powered Devices (PD) that connect into Power over

Ethernet (PoE) systems. The LM5071 is specifically de-

signed for the PD that must accept power from auxiliary

sources such as ac adapters. The auxiliary power inter-

face 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 in-

terface and switch mode power supply (SMPS) are inte-

grated into the IC.

Features

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Compatible with 12V ac adapters

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Fully Compliant 802.3af Power Interface Port

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80V, 1

Ω, 400 mA Internal MOSFET

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Detection Resistor Disconnect Function

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Programmable Classification Current

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Programmable Under-voltage Lockout with

Programmable Hysteresis

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Thermal Shutdown Protection

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Auxiliary Power Enable Pin

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Current Mode Pulse Width Modulator

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Supports both Isolated and Non-Isolated Applications

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Error Amplifier and Reference for Non-Isolated

Applications

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Programmable Oscillator Frequency

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Programmable Soft-start

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80% Maximum Duty Cycle Limiter, Slope Compensation

(-80 device)

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50% Maximum Duty Cycle Limiter, No Slope

Compensation (-50 device)

Packages

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TSSOP-16

Block Diagram

20168401

November 2005

© 2005 National Semiconductor Corporation

DS201684

www.national.com