Linear LTCR4268-1 35W PoE解决方案

Linear 的LTCR4268-1是集成了同步NoOpto Flyback控制器的大功率以太网供电(PD)器件,适用于IEEE 802.3af和高达35W的大功率PoE应用.该器件包括精密的双值限流,使得过冲电流在IEEE 802.3af的限流以下,从而保证了电流750mA供电的安全应用. LTCR4268-1同步的电流模式反激控制器在单次转换中能产生多种电源值,以获得最大的系统效率,同时维持所有输出的精密调整.本文提供了LCTR4268-1的主要性能和应用电路图.

LTCR4268-1High Power PD with Synchronous NoOpto Flyback Controller
The LTCR4268-1 is an integrated Powered Device (PD) controller and switching regulator intended for IEEE 802.3af and high power PoE applications up to 35W. By including a precision dual current limit, the LTC4268-1 keeps inrush below IEEE 802.3af current limit levels to ensure interoperability success while enabling high power applications with a 750mA operational current limit.

The LTC4268-1 synchronous, current-mode, flyback controller generates multiple supply rails in a single conversion providing for the highest system efficiency while maintaining tight regulation across all outputs. The LTC4268-1 includes Linear Technology’s patented NoOpto feedback topology to provide full IEEE 802.3af isolation without the need of optoisolator circuitry.

The oversized power path and high performance flyback controller of the LTC4268-1 combine to make the ultimate solution for power hungry PoE applications such as WAPs,
PTZ security cameras, RFID readers and ultra-efficient 802.3af applications running near the 12.95W limit.

The LTC4268-1 is available in a space saving 32-pin DFN package.
主要特性:

Robust 35W PD Front End
IEEE 802.3afR Compliant
Rugged 750mA Power MOSFET with Precision Dual Level Current Limit
High Performance Synchronous Flyback Controller
IEEE Isolation Obtained without an Optoisolator
Adjustable Frequency from 50kHz to 250kHz
Tight Multi-Output Regulation with Load Compensation
On-board 25k Signature Resistor
Programmable Classifi cation Current to 75mA
Complete Thermal and Over-Current Protection
Available in Compact 32-Pin 7mm x 4mm DFN Package

应用范围:
VoIP Phones with Advanced Display Options
Dual-Radio Wireless Access Points
PTZ Security Cameras
RFID Readers
Industrial Controls
Magnetic Card Readers
High Power PoE Systems

Fig.1典型应用电路图



Fig 2. 4路大功率PoE 吉比特以太网(GbE)



Fig3 辅助电源和PD的接口

选择1:



选择2:



选择3:



选择4:



Fig.4:30W高效率三输出PD电路图.