LTC4258

1

4258p

, LTC and LT are registered trademarks of Linear Technology Corporation.

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Controls Four Independent – 48V Powered

Ethernet Ports

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Each Port Includes:

– IEEE 802

Classification

– Output Current Limit with Foldback

– Short-Circuit Protection with Fast Gate Pull-Down

– PD Disconnect Using DC Sensing

– Power Good Indication

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TM

Serial Interface

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4-Bit Programmable Digital Address Allows Control

of Up to 64 Ports

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Programmable INT Pin Eliminates Software Polling

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Current and Duty Cycle Limits Protect External FETs

Quad IEEE 802.3af

Power over Ethernet Controller

with Integrated Detection

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IEEE 802.3af Compliant Endpoint and Midspan

Power Sources

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IP Phone Systems

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DTE Power Distribution

The LTC

signed for use in IEEE 802.3af compliant Power

Sourcing Equipment (PSE). It consists of four independent

ports, each with output current limit, short-circuit protec-

tion, complete Powered Device (PD) detection and classi-

fication capability, and programmable PD disconnect using

AC or DC sensing. Used with power MOSFETs and passives

as in Figure 1, the LTC4258 can implement a complete IEEE

802.3af-compliant PSE.

The LTC4258 can operate autonomously or be controlled by

the same data bus, allowing up to 64 powered Ethernet ports

to be controlled with only two digital lines. Fault conditions

are optionally signaled with the INT pin to eliminate software

polling.

External power MOSFETs, current sense resistors and di-

odes allow easy scaling of current and power dissipation

levels and provide protection against voltage and current

spikes and ESD events.

The LTC4258 is available in a 36-pin SSOP package.

Linear Technology also provides solutions for 802.3af PD

applications with the LTC4257 and LTC4257-1.

Hot Swap is a trademark of Linear Technology Corporation. 802 is a registered trademark of

Figure 1. Complete 4-Port Powered Ethernet Power Source

DGND

AD3

RS1 TO RS4: 0.5

Ω

Q1 TO Q4: IRFM120A

AD2

AD1

AD0

SDAOUT

SDAIN

SCL

DETECT4

DETECT3

DETECT1

DETECT2

AGND

INT

–48V

SHDN1

SENSE1

GATE1

Q1

Q2

Q3

Q4

CMPD3003

×4

10k

10k

10k

10k

OUT1

OUT2

OUT3

OUT4

4258 F01

SMAJ58A

×4

0.1

µF 100V

×4

OUT1 SENSE2 GATE2

LTC4258

OUT2 SENSE3 GATE3 OUT3 SENSE4 GATE4 OUT4

SHDN2 SHDN3 SHDN4

3.3V

0.1

µF

AUTO BYP

RESET

0.1

µF

100V X7R

0.1

µF

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

Electrical Specifications Subject to Change