Linear公司的LTCR4270/LTC4271芯片组是12端口PSE控制器,专为IEEE 802.3at Type 1 and Type 2大功率兼容的PoE系统而设计,采用变压器隔离通信协议来替代昂贵的光耦合器,可提供PD的最大功率为90W,支持两对和4对输出功率,1MHz I2C兼容的串行控制接口,主要用在PoE PSE交换/路由器和PoE PSE中跨.本文介绍了LTCR4270/LTC4271主要特性,典型应用电路和PoE系统框图.

The LTCR4270/LTC4271 chipset is a 12-Port Power Sourcing Equipment (PSE) controller designed for use in IEEE 802.3at Type 1 and Type 2 (high power) compliant Power over Ethernet (PoE) systems. Transformer-isolated communication protocol replaces expensive opto-couplers and complex isolated 3.3V supply resulting in significant BOM cost savings. The LTC4270/LTC4271 chipset delivers lowest-in-industry heat dissipation by utilizing low-RDS(ON) external MOSFETs and 0.25Ω sense resistors.

Advanced power management features include per-port 12- bit current monitoring ADCs, DAC-programmable current limit, and versatile fast shut-down of preselected ports.

Advanced power management host software is available under a no-cost license. PD Discovery uses a proprietary dual-mode 4-point detection mechanism ensuring excellent immunity from false PD detection. Midspan PSEs are supported with 2-event classification and a 2 second backoff timer. The LTC4270/LTC4271 includes an I2C serial interface operable up to 1MHz.

The LTC4270/LTC4271 is available in multiple power grades allowing delivered PD power up to 90W.

LTCR4270/LTC4271主要特性:

12 Independent PSE Channels

Compliant with IEEE 802.3at Type 1 and 2

Chipset Provides Electrical Isolation

Reduced BOM Cost

Eliminates up to 6 High Speed Opto-Couplers

Eliminates Isolated 3.3V Power Supply

Low Power Dissipation

0.25Ω Sense Resistance Per Channel

Very High Reliability 4-Point PD Detection

2-Point Forced Voltage

2-Point Forced Current

Temperature Monitoring

VEE and VPORT Monitoring

1 Second Rolling IPORT Averaging

Supports 2-Pair and 4-Pair Output Power

1MHz I2C Compatible Serial Control Interface

Available In Three Power Grades

A-Grade – LTPoE++™ 35W to 90W

B-Grade – PoE+ 25.5W

C-Grade – PoE 13W

Available In 52-Lead 7mmx8mm (LTC4270) and 24-Lead 4mm x4mm (LTC4271) QFN Packages

LTCR4270/LTC4271应用:

PoE PSE Switches/Routers

PoE PSE Midspans



图1.LTCR4270/LTC4271典型应用电路(1)

图2.LTCR4270/LTC4271 PoE系统框图

图3.LTCR4270/LTC4271专用解决方案电路

图4.LTCR4270/LTC4271典型应用电路(2)
详情请见:
http://cds.linear.com/docs/Datasheet/42701f.pdf