Maxim MAX5995B IEEE 802．3bt兼容PD接口控制器解决方案

Maxim公司的MAX5995A/MAX5995B/MAX5995C是IEEE 802.3bt兼容的集成了91W大功率MOSFET的供电设备接口控制器,主要用在以太网供电系统(PoE).器件提供了PD和检测标识,分类标识和集成的具有起动浪涌电流控制的隔离功率开关,简化的墙适配器接口,多事件分类0-8,100V输入最大指标,睡眠模式和超低功耗睡眠模式,主要用在IEEE 802.3bt供电设备,VOIP电话,IP安全班照相机,无线接入点,小型基站和微型基站,照明和建筑物自动化.本文介绍了MAX5995B主要优势和特性,框图, 典型应用电路图以及评估板MAX5995 EVK主要特性,电路图材料清单和PCB设计图.
The MAX5995A/MAX5995B/MAX5995C provide a complete interface for a powered device (PD) to comply with the IEEER 802.3af/at/bt standard in a Power-Over-Ethernet(PoE) system. The devices provide the PD with a detection signature, classification signature, and an integrated isolation power switch with startup inrush current control.
During the startup period, the devices limit the current to 135mA (typ) before switching to the higher current limit (1800mA to 2400mA, typ) when the isolation power MOSFET is fully enhanced. The devices feature Multi-Event classification, Intelligent MPS (MAX5995B/MAX5995C), Autoclass (MAX5995C), an input UVLO with wide hysteresis and long deglitch time to compensate for twistedpair cable resistive drop and to assure glitch-free transition during power-on/-off conditions. The devices can withstand a maximum voltage of 100V at the input.
The devices support a Multi-Event classification method, as specified in the IEEE 802.3bt standard, and provide a signal to indicate from Type 1 to Type 4 Power Sourcing Equipment (PSE). The devices can detect the presence of a wall adapter power source connection and allow a smooth switch-over from the PoE power source to the wall power adapter.
The devices also provide a power-good (PG) signal, twostep current limit and foldback control, overtemperature protection. A sleep mode feature in the MAX5995A/MAX5995B minimizes low power consumption while generating the Maintain Power Signature (MPS) to maintain PSE co...