LTC4278 Linear Technology, LTC4278 Datasheet

LTC4278

Manufacturer Part Number

LTC4278

Description

IEEE 802.3at PD

Manufacturer

Linear Technology

Datasheet

1.LTC4278.pdf (40 pages)

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FEATURES

APPLICATIONS

TYPICAL APPLICATION

25.5W IEEE 802.3at Compliant (Type 2) PD

10V to 57V Auxiliary Power Input

Shutdown Pin for Flexible Auxiliary Power Support

Integrated State-of-the-Art No-Opto Synchronous

Flyback Controller

– Isolated Power Supply Efﬁ ciency >92%

– 88% Efﬁ ciency Including Diode Bridge and

Superior EMI Performance

Robust 100V 0.7Ω (Typ) Integrated Hot Swap MOSFET

IEEE 802.3at High Power Available Indicator

Integrated Signature Resistor and Programmable

Class Current

Undervoltage, Overvoltage and Thermal Protection

Short-Circuit Protection with Auto-Restart

Programmable Soft-Start and Switching Frequency

Complementary Power Good Indicators

Thermally Enhanced 7mm × 4mm DFN Package

VoIP Phones with Advanced Display Options

Dual-Radio Wireless Access Points

PTZ Security Cameras

RFID Readers

Industrial Controls

Hot Swap™ FET

(10V TO 57V)

SPARE PAIR

AUXILIARY

DATA PAIR

54V FROM

SUPPLY

–

PDS5100H

0.1μF

100k

680k

24k

BSS63LT1

30.9Ω

25W PD Solution with 12V Auxiliary

41.2k

294k

SHDN

10μF

UVLO PWRGD

PORTP

CLASS

PORTN

NEG

Controller and 12V Aux Support

SYNC

2.2μH

Synchronous No-Opto Flyback

CONTROLLER

GND

TO MICRO

T2P

OSC

10μF

33pF

PGDLY

DESCRIPTION

The LTC

controller and switching regulator intended for high power

IEEE 802.3at and 802.3af applications. With a wide input

voltage range, the LTC4278 is speciﬁ cally designed to sup-

port PD applications that include a low-voltage auxiliary

power input such as a 12V wall adaptor. The inclusion of

a shutdown pin provides simple implementation of both

PoE and auxiliary dominate applications. In addition, the

LTC4278 supports both 1-event and 2-event classiﬁ cations

as deﬁ ned by the IEEE, thereby allowing the use in a wide

range of product conﬁ gurations.

The LTC4278 synchronous, current mode, ﬂ yback control-

ler generates multiple supply rails in a single conversion

step providing for the highest system efﬁ ciency while main-

taining tight regulation across all outputs. The LTC4278

includes Linear Technology’s patented No-Opto feedback

topology to provide full IEEE 802.3 isolation without the

need of an opto-isolator circuit. A true soft-start function

allows graceful ramp-up of all output voltages.

The LTC4278 is available in a space saving 32-pin DFN

package.

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear

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

All other trademarks are the property of their respective owners. Protected by U.S. Patents,

including 5841643.

LTC4278

10k

21.5k

3.01k

100k

ENDLY

4278 is an integrated Powered Device (PD)

38.3k

CMP

1μF

1.8k

IEEE 802.3at PD with

SENSE

CMP

0.1μF

–

FDMS2572

12mΩ

EPC3472G-LF

•

1μF

•

2.2nF

HAT2169

LTC4278

0.18μH

47μF

4278 TA01a

100μF

4278f

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