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EVALUATION KIT AVAILABLE
IEEE 802.3af-Compliant, High-Efficiency,
Class 1/Class 2, PDs with Integrated
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 perfor-
mance 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.
Ordering Information appears at end of data sheet.
IEEE is a registered service mark of the Institute of Electrical
and Electronics Engineers, Inc.
WiMAX is a registered certification mark and registered service
mark of WiMAX Forum.
Benefits and Features
●● High Integration Saves Space and BOM Cost
• Efficient, Integrated DC-DC Converter (with
• 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
●● IEEE 802.3af-Compliant Features Reduce Design Time
• PoE Class 1/Class 2 Classification Set with
• 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
• Sleep and Ultra-Low-Power Mode (MAX5986A/
• Frequency Foldback for High-Efficiency Light-Load
• 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 (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
●● IEEE 802.3af-Powered Devices
●● IP Phones
●● Wireless Access Nodes
●● IP Security Cameras
●● WiMAX® Base Stations
19-6261; Rev 7; 11/18