Top

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

Highly Integrated Powered Devices Reduce BOM Cost and Improve Efficiency

Product Details

Key Features

Parametric specs for Powered Devices
Compliance IEEE 802.3af
RDS(ON) (Ω) (PD MOSFET) 1.2
PWM Yes
Switching Frequency (kHz) 275
UVLO Threshold (V) 38.6
Package/Pins TQFN/16
Oper. Temp. (°C) -40 to +85
Budgetary
Price (See Notes)
3.8
Parametric specs for Step-Down Switching Regulators
VIN (V) (min) 8.7
VIN (V) (max) 60
VOUT1 (V) (min) 3
VOUT1 (V) (max) 5.6
IOUT1 (A) (max) 1.2
Switch Type Internal
Preset VOUT (V) 3.3
Output Adjust. Method Resistor
Synchronous Switching? Yes
# DC-DC Outputs 1
Switching Frequency (kHz) 275
Package/Pins TQFN/16
View Less

Simplified Block Diagram

Technical Docs

Support & Training

Search our knowledge base for answers to your technical questions.

Filtered Search

Our dedicated team of Applications Engineers are also available to answer your technical questions. Visit our support portal .

Parameters

Parametric specs for Powered Devices
Compliance IEEE 802.3af
RDS(ON) (Ω) (PD MOSFET) 1.2
PWM Yes
Switching Frequency (kHz) 275
UVLO Threshold (V) 38.6
Package/Pins TQFN/16
Oper. Temp. (°C) -40 to +85
Budgetary
Price (See Notes)
3.8
Parametric specs for Step-Down Switching Regulators
VIN (V) (min) 8.7
VIN (V) (max) 60
VOUT1 (V) (min) 3
VOUT1 (V) (max) 5.6
IOUT1 (A) (max) 1.2
Switch Type Internal
Preset VOUT (V) 3.3
Output Adjust. Method Resistor
Synchronous Switching? Yes
# DC-DC Outputs 1
Switching Frequency (kHz) 275
Package/Pins TQFN/16

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 (MAX5987A)
  • IEEE 802.3af-Compliant Features Reduce Design Time
    • 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 (MAX5986A/MAX5986B/MAX5986C)
    • Frequency Foldback for High-Efficiency Light-Load 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 (Active-Low RESET) Output (MAX5987A)
  • Flexible and Easy to Design With
    • 3.0V to 14V Programmable Output Voltage Range
    • Internal Compensation
    • Fixed 215kHz/430kHz Switching Frequency
    • Fixed 3.3V or Adjustable Output Voltage through an External Resistive Divider

Applications/Uses

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

Description

The MAX5986A–MAX5986C/MAX5987A 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 MAX5987A includes a low-dropout regulator and the MAX5986A–MAX5986C include 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 323mA 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 8.7V to 60V and supports up to 6.49W of input power. The MAX5986A/MAX5986B/MAX5987A operate at a fixed 215kHz switching frequency and the MAX5986C operates at a fixed 430kHz switching frequency. The DC-DC converter operates at a fixed 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.

The MAX5986A–MAX5986C/MAX5987A are available in a 16-pin, 5mm x 5mm, TQFN power package and operate over the -40°C to +85°C temperature range.

Simplified Block Diagram

MAX5986A, MAX5987A: Functional Diagram MAX5986A, MAX5987A: Functional Diagram Zoom icon

Technical Docs

Support & Training

Search our knowledge base for answers to your technical questions.

Filtered Search

Our dedicated team of Applications Engineers are also available to answer your technical questions. Visit our support portal .