MAX5986A/MAX5986B/MAX5987A

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

Class 2, PDs with Integrated DC-DC Converter

19-6261; Rev 1; 12/12

Benefits and Features

S

IEEE 802.3af Compliant

S

PoE Class 1/Class 2 Classification

S

Simplified Wall Adapter Interface

S

Intelligent MPS

S

Sleep and Ultra-Low-Power Mode (MAX5986A/

MAX5986B)

S

Efficient, Integrated DC-DC Converter (with

Integrated Switches)

S

8.7V to 60V Wide Input Voltage Range

S

3.0V to 14V Programmable Output Voltage Range

S

Internal Compensation

S

Fixed 214kHz/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

General Description

The MAX5986A/MAX5986B/MAX5987A provide a com-

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/MAX5986B

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 201mA (MAX5986A) or 323mA (MAX5986B/

MAX5987A) 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

(MAX5986A) or 6.49W (MAX5986B/MAX5987A) of input

power. The MAX5986A operates at a fixed 275kHz

switching frequency, while the MAX5986B/MAX5987A

operate at a fixed 215kHz switching frequency. The

DC-DC converter operates at a fixed 275kHz switch-

ing 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/MAX5986B/MAX5987A are available in a

16-pin, 5mm x 5mm, TQFN power package and operate

over the -40°C to +85°C temperature range.

Applications

IEEE 802.3af-Powered Devices

IP Phones

Wireless Access Nodes

IP Security Cameras

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.

Ordering Information appears at end of data sheet.

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

refer to www.maximintegrated.com/MAX5986A/MAX5987A.related.

EVALUATION KIT AVAILABLE

For pricing, delivery, and ordering information, please contact Maxim Direct at

1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.