MAX5988, MAX5988A, MAX5988B

IEEE 802.3af-Compliant, High-Efficiency, Class 1/Class 2 Powered Devices with Integrated DC-DC Converters

Reduce BOM Costs with Highly Integrated Powered Devices for PoE Applications


Description

The MAX5988A/MAX5988B provide a complete power-supply 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-to-implement architecture with a fast transient response. The step-down converter operates in a wide input voltage range from 8.8V to 60V and supports up to 6.49W of input power at 1.3A load. The DC-DC converter operates at a fixed 215kHz switching frequency, with an efficiency-boosting 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°C to +85°C temperature range.

MAX5988A, MAX5988B: Functional Diagram MAX5988A, MAX5988B: Functional Diagram Enlarge+

Key Features

  • 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
  • Application-Specific Features Speed Design
    • IEEE 802.3af Compliant
    • PoE Class 1/Class 2 Classification Set with Single Resistor
    • Intelligent Maintain Power Signature (MPS)
    • 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 Light-Load Operation
    • Back-Bias Capability to Optimize the Efficiency
  • Robust Performance
    • 8.8V to 60V Wide Input Voltage Range
    • Hiccup-Mode Runaway Current Limit
    • 49mA (typ) Inrush Current Limit
    • Open-Drain (Active-Low RESET) Output
  • Easy to Design With
    • 3.0V to 14V Programmable Output Voltage Range
    • Internal Compensation
    • Fixed 215kHz Switching Frequency
    • Fixed 3.3V or Adjustable Output Voltage through an External Resistive Divider (LDO)

Applications/Uses

  • IEEE® 802.3af-Powered Devices
  • IP Phones
  • IP Security Cameras
  • WiMAX® Base Stations
  • Wireless Access Nodes
Part Number Compliance RDS(ON)
(Ω)
PWM UVLO Threshold
(V)
Package/Pins Oper. Temp.
(°C)
Budgetary
Price
PD MOSFET See Notes
MAX5988A 
IEEE 802.3af
IEEE 802.3at
1.2 No 38.6
TQFN/20
-40 to +85 $3.41 @1k
MAX5988B 
TQFN/20
See All Powered Devices (30)
Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

Quality and Environmental Data

Request Reliability Report for: MAX5988  MAX5988A  MAX5988B 
Lead-Free Package Tin (Sn) Whisker Reports

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