MAX5986A Datasheet, PDF(1/20 Page) Maxim Integrated Products – IEEE 802.3af-Compliant, High-Efficiency, Class 1,Powered Devices with Integrated DC-DC Converter

19-6261; Rev 0; 4/12

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MAX5986A/MAX5987A

IEEE 802.3af-Compliant, High-Efficiency, Class 1,

Powered Devices with Integrated DC-DC Converter

General Description

The MAX5986A/MAX5987A provide a complete power-

supply solution as IEEEÂ® 802.3af-compliant Class 1

Powered Devices (PDs) in a Power-over-Ethernet (PoE)

system. The MAX5986A/MAX5987A 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 includes

sleep and ultra-low power modes.

The PD interface provides a detection signature and a

Class 1 classification signature with a single external

resistor. The PD interface also provides an isolation

power MOSFET, a 60mA (max) inrush current limit, and a

201mA (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 volt-

age range from 8.7V to 60V and supports up to 3.84W

of input power at 1.15A load. The DC-DC converter

operates at a fixed 275kHz 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 condi-

tions. The devices also feature overtemperature shut-

down, short-circuit protection, output overvoltage protec-

tion, and hiccup current limit for enhanced performance

and reliability.

The MAX5986A/MAX5987A are available in a 16-pin,

5mm x 5mm, TQFN power package and operate over the

-40Â°C to +85Â°C temperature range.

Applications

IEEE 802.3af-Powered Devices

IP Phones

Wireless Access Nodes

IP Security Cameras

WiMAXÂ® Base Stations

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

S IEEE 802.3af Compliant

S PoE Class 1 Classification

S Simplified Wall Adapter Interface

S Efficient, Integrated DC-DC Converter (with

Integrated Switches)

S 8.7V to 60V Wide Input Voltage Range

S 3.0V to 5.6V Programmable Output Voltage Range

S Internal Compensation

S Fixed 275kHz Switching Frequency

S Frequency Foldback for High-Efficiency Light-

Load Operation

S Built-In Output-Voltage Monitoring

S Open-Drain RESET Output (MAX5987A)

S Protects Against Overload, Output Short Circuit,

Output Overvoltage, and Overtemperature

S Hiccup-Mode Runaway Current Limit

S Back-Bias Capability to Optimize the Efficiency

S Integrated TVS Diode Withstands Cable Discharge

Event (CDE)

S Internal LDO Regulator with Up to 100mA Load

(MAX5987A)

S Fixed 3.3V or Adjustable Output Voltage Through

an External Resistive Divider

S 49mA (typ) Inrush Current Limit

S Pass 2kV, 200m CAT-6 Cable Discharge Event

Ordering Information appears at end of data sheet.

For related parts and recommended products to use with this part,

refer to www.maxim-ic.com/MAX5986A/MAX5987A.related.

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maximâs website at www.maxim-ic.com.

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