MAXIM MAX5991AETP+T

The MAX5991A/MAX5991B provide a complete powersupply solution as IEEE 802.3af-compliant Class 1/ Class 2 Powered Devices (PDs) in a Power-over-Ethernet (PoE) system. The devices integrate the PD interface with an efficient DC-DC converter, offering a low external part count PD solution. The devices also include a low-dropout regulator, MPS, sleep, and ultra-low power modes. The PD interface provides a detection signature and a Class 1/Class 2 classification signature with a single external resistor. The PD interface also provides an isolation power MOSFET, a 60mA (max) inrush current limit, and a 321mA (typ) operating current limit. The integrated step-down DC-DC converter uses a peak current-mode control scheme and provides an easy-toimplement architecture with a fast transient response. The step-down converter operates in a wide input voltage range from 8.7V to 60V and supports up to 6.49W of input power at 1.3A load. The DC-DC converter operates at a fixed 430kHz switching frequency, with an efficiencyboosting frequency foldback that reduces the switching frequency by half at light loads. The devices feature an input undervoltage-lockout (UVLO) with wide hysteresis and long deglitch time to compensate for twisted-pair cable resistive drop and to assure glitch-free transition during power-on/-off conditions. The devices also feature overtemperature shutdown, short-circuit protection, output overvoltage protection, and hiccup current limit for enhanced performance and reliability. All devices are available in a 20-pin, 4mm×4mm, TQFN power package and operate over the -40℃ to +85℃ temperature range.

• High Integration Saves Space and BOM Cost
• Efficient, Integrated DC-DC Converter (with Integrated Switches)
• Built-In Output-Voltage Monitoring Protects Against Overload, Output Short Circuit, Output Overvoltage, and Overtemperature
• Integrated TVS Diode Withstands Cable Discharge Event (CDE)
• Internal LDO Regulator with Up to 100mA Load
• PoE Class 1/Class 2 Classification Set with Single Resistor
• Intelligent Maintain Power Signature (MPS) Complies with IEEE 802.3af Specification
• Simplified Wall Adapter Interface
• Pass 2kV, 200m CAT-6 Cable Discharge Event
• High Efficiency During Light Loads Reduces Power Consumption
• Sleep and Ultra-Low-Power Mode
• Frequency Foldback for High-Efficiency LightLoad Operation
• Back-Bias Capability to Optimize the Efficiency
• Robust Performance
• 8.7V to 60V Wide Input Voltage Range
• Hiccup-Mode Runaway Current Limit
• 49mA (typ) Inrush Current Limit
• Open-Drain RESET Output
• Easy to Design With
• 3.2V to 14V Programmable Output Voltage Range
• Internal Compensation
• Fixed 430kHz Switching Frequency

• IEEE 802.3af-Powered Devices
• IP Phones
• Wireless Access Nodes
• IP Security Cameras
• WiMAX Base Stations