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2019年第02期
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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，小型和微型，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.
调整脚>7-adcaThe 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 connection. An Ultra-Low-Power sleep mode feature in the
MAX5995A/MAX5995B further reduces power consumption while still generating MPS current. The MAX5995B/MAX5995C provides Intelligent Maintain Power Signature (IMPS) feature to automatically enable MPS current by detecting the port current.The devices feature a LED driver that is activated during sleep mode, Ultra-Low-Power sleep mode(MAX5995A/MAX5995B), and Intelligent MPS
mode(MAX5995B/MAX5995C). Multi-Event indication feature provides patterned signals to indicate power level allocated from PSE to PD in 5 different scenarios.
The MAX5995C provides Autoclass feature to enable advanced applications that allow the PSE to effectively optimize power allocation to
PD.
Maxim MAX5995B IEEE 802．3bt 兼容PD 接口控制器解决方案
