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LTC4274 Single IEEE 802.3at Power Over Ethernet Controller FEATURES DESCRIPTION

Compliant with IEEE 802.3at Type 1 and 2 Supports Proprietary Very High Power Up to 50W 0.34 Total Channel Resistance 130mW at 600mA Advanced Power Management 8-Bit Programmable Current Limit (ILIM) 7-Bit Programmable Overload Currents (ICUT) Fast Shutdown 14.5-Bit Port Current/Voltage Monitoring 2-Event Classification Very High Reliability 4-Point PD Detection: 2-Point Forced Voltage 2-Point Forced Current High Capacitance Legacy Device Detection LTC4259A-1 and LTC4266 SW Compatible 1MHz I2C Compatible Serial Control Interface Midspan Backoff Timer Available in 38-Pin 5mm x 7mm QFN Package
The LTC (R)4274 is a single Power Sourcing Equipment (PSE) controller designed for use in IEEE 802.3 Type 1 and Type 2 (high power) compliant Power over Ethernet (PoE) systems. The LTC4274 is also a good choice for proprietary PoE PSE systems, which may require more power than the new IEEE 802.3at standard allows. The LTC4274 can source up to 50W while otherwise remaining compatible with IEEE 802.3at. The LTC4274 delivers lowest-in-industry heat dissipation by utilizing a low RON external MOSFET and a 0.25 sense resistor, eliminating the need for expensive heat sinks. An external MOSFET also provides a more robust solution compared to an integrated MOSFET. Advanced power management features include: selectable high speed 9.5-bit (1kHz) or high resolution 14.5-bit current and voltage readback, a 7-bit DAC for overcurrent threshold (ICUT ), a unique nonlinear 8-bit programmable current limit (ILIM) and versatile quick shutdown. PD Discovery uses a proprietary dualmode 4-point detection mechanism ensuring the best immunity from false PD detection. Midspan PSEs are supported with 2-event classification and a two second backoff timer. Legacy high-capacitance device detection is available. The LTC4274 includes an I2C serial interface operable up to 1MHz.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
APPLICATIONS

PoE PSE Switches/Routers PoE PSE Midspans
TYPICAL APPLICATION
Complete Ethernet High Power Source
3.3V 0.1F
INT SCL SDAIN SDAOUT AD0 AD1 AD2 AD3 DGND AGND 1F 100V
SHDN
VDD AUTO MSD RESET MID GATE OUT S1B 0.22F 100V PORT
4274 TA01
LTC4274
VEE SENSE
SMAJ58A -54V
S1B -54V
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LTC4274 Product Brief BENEFITS

Lowest Channel Resistance Eliminates Heat Sinks First Fully IEEE 802.3at-Compliant Single PSE
Linear's Experienced and Dedicated PoE Team Linear Technology's team provides timely technical support and optimum performance at the lowest overall cost with fastest time to market.
LAYER 2 CLASSIFICATION (DATA LAYER) IS INTENDED FOR ENDPOINT PSEs. USES LINK LAYER DISCOVERY PROTOCOL (LLDP) PSE VOLTAGE CLASS EVENT #1 CLASS EVENT #2
LAYER 1 CLASSIFICATION (POWER LAYER) IS INTENDED FOR MIDSPANS. ON RANGE TRANSITION TO ON RANGE VIA CLASS EVENT #3
MARK EVENT #1 MARK EVENT #2 CLASS RANGE
DETECT RANGE
MARK RANGE
RESET RANGE
TIME
LTC4274 Voltage Probe During 2-Event Classification
LTC4274 Size Comparison
RELATED PARTS
PART NUMBER LTC4264 LTC4265 LTC4268-1 LTC4269-1 LTC4269-2 LTC4278 LTC4263-1 LTC4266 PSE/PD PD PD PD PD PD PD PSE PSE CHANNELS DESCRIPTION 1 1 1 1 1 1 1 4 Pre-Standard High Power PD PoE Interface Controller (35W) IEEE 802.3at High Power PD PoE+ Interface Controller (25.5W) Pre-Standard High Power PD PoE Interface Controller with Integrated Synchronous Switching Regulator (35W) IEEE 802.3at High Power PD PoE+ Interface Controller with Integrated Synchronous No-Opto Flyback Switching Regulator (25.5W) IEEE 802.3at High Power PD PoE+ Interface Controller with Integrated Synchronous Forward Converter (25.5W) IEEE 802.3at High Power PD PoE+ Interface Controller with Integrated Synchronous No-Opto Flyback Switching Regulator (25.5W), 12V Auxiliary Support High Power IEEE 802.3af PSE Controller with Internal Switch Supports IEEE 802.3at Type 1 and Type 2 PDs, 0.34 Channel Resistance, Advanced Power Management, High Reliability 4-Point PD Detection, Legacy Capacitance Detect PACKAGE 4mm x 3mm DFN-12 4mm x 3mm DFN-12 7mm x 4mm DFN-32 7mm x 4mm DFN-32 7mm x 4mm DFN-32 7mm x 4mm DFN-32 4mm x 3mm DFN-14 SO-14 5mm x 7mm DFN-38 SSOP-36
INFO AND SAMPLES
* Visit http://www.linear.com/contact/ or call 1-800-4-LINEAR to find contact information for the sales office or distributor near you. * Visit http://www.linear.com/poe for more information about PoE and PoE+ products.
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 FAX: (408) 434-0507
LT 1009 * PRINTED IN USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2009

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