器件名称: DI-88
功能描述: PoE Detection and Classification (Class 0-3) Interface Circuit
文件大小: 301.65KB 共2页
简 介:Classication (Class 0-3) Interface Circuit
Application PoE/VoIP Device DPA423G Power Output 6.49 W Input Voltage 36-57 VDC Output Voltage 3.3 V Topology Flyback
Design Idea DI-88 DPA-Switch PoE Detection and
Design Highlights
Simple interface for Power Over Ethernet (PoE) Powered Devices (PDs) Includes PoE detection and classication circuits for all classes (0, 1, 2 and 3) Compliance to IEEE802.3af PoE standards veried by University of New Hampshire Interopability Consortium (UNH-IOC)* Includes under voltage lockout (42 VDC on, 34 VDC off)
Classication occurs as the input voltages rises from 14.5 to 20.5 VDC. The sending device determines the class of the PD by monitoring the amount of current drawn by the PD during this phase. For classes 1, 2 and 3, the classication current (ICL), is programmed by resistor R34, as per the table. Class 0 1 2 3 POUT (min) W 0.44 0.44 3.84 6.49 POUT (max) W 12.95 3.84 6.49 12.95 ICL (min) mA 0.5 9 17 26 ICL (max) mA 4 12 20 30 R34 Ohms 133 69.8 45.3
PoE Detection and Classication
PoE is becoming widely adopted for networking and VoIP telecom applications. A typical PD solution is shown in Figure 1 and has a PoE interface circuit and a DPA-Switch DC-DC converter block (see EPR-68 for full details of operation of the DC-DC converter). The PoE specification requires the PD to implement three functions: detection, classication and pass-switch connection. Detection occurs as the input voltages rises from 2.5 to 10 VDC. Resistor R31 within ……
