General Description

The MAX5940A/MAX5940B/MAX5940C/MAX5940D pro-

vide complete interface function for a powered device

(PD) to comply with the IEEE 802.3af standard in a

power-over-ethernet system. MAX5940A/MAX5940B/

MAX5940C/MAX5940D provide the PD with a detection

signature, a classification signature, and an integrated

isolation switch with programmable inrush current control.

These devices also feature power-mode undervoltage

lockout (UVLO) with wide hysteresis and power-

good outputs. The MAX5940A/MAX5940B are available

with an absolute maximum rating of 80V and the

MAX5940C/MAX5940D are rated for an absolute maxi-

mum rating of 90V.

An integrated MOSFET provides PD isolation during

detection and classification. All devices guarantee a leak-

age current offset of less than 10µA during the detection

phase. A programmable current limit prevents high inrush

current during power-on. The device features power-

mode UVLO with wide hysteresis and long deglitch time

to compensate for twisted-pair cable resistive drop and to

assure glitch-free transition between detection, classifica-

tion, and power-on/-off phases.

The MAX5940A/MAX5940C provide an active-high

(PGOOD) open-drain output and a fixed UVLO threshold.

The MAX5940B/MAX5940D provide both active-high

(PGOOD) and active-low (PGOOD) outputs and have an

adjustable UVLO threshold with the default value compli-

ant to the 802.3af standard. All devices are designed to

work with or without an external diode bridge.

The MAX5940A/MAX5940B/MAX5940C/MAX5940D are

available in 8-pin SO packages and are rated over the

extended temperature range of -40°C to +85°C.

Applications

IP Phones

Security Cameras

Wireless Access Nodes

IEEE 802.3af Power Devices

Computer Telephony

Features

♦ Fully Integrated IEEE 802.3af-Compliant PD

Interface

♦ PD Detection and Programmable Classification

Signatures

♦ Less than 10µA Leakage Current Offset During

Detection

♦ Integrated MOSFET For Isolation and Inrush

Current Limiting

♦ 90V Absolute Maximum Rating

(MAX5940C/MAX5940D)

♦ Gate Output Allows External Control of the

Internal Isolation MOSFET

♦ Programmable Inrush Current Control

♦ Programmable Undervoltage Lockout

(MAX5940B/MAX5940D Only)

♦ Wide UVLO Hysteresis Accommodates Twisted-

Pair Cable Voltage Drop

♦ PGOOD/PGOOD Outputs to Enable Downstream

DC-DC Converters

♦ -40°C to +85°C Operating Temperature Range

IEEE 802.3af PD Interface Controller

For Power-Over-Ethernet

________________________________________________________________ Maxim Integrated Products

1

Ordering Information

60V

68nF

GND

GATE

RCLASS

PGOOD

DC-DC CONVERTER

GND

-48V

*OPTIONAL.

GND

V+

LOAD

D1*

OUT

2

3

4

5

6

8

25.5k

Ω

SS_SHDN

MAX5014

MAX5940A

MAX5940C

D2*

Typical Operating Circuits

19-2991; Rev 2; 2/06

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

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

EVALUATION

KIT

AVAILABLE

Pin Configurations appear at end of data sheet.

PART

TEMP RANGE

PIN-

PACKAGE

UVLO

MAX5940AESA

-40°C to +85°C

8 SO

Fixed

MAX5940BESA

-40°C to +85°C

8 SO

Adjustable

MAX5940CESA

-40°C to +85°C

8 SO

Fixed

MAX5940DESA

-40°C to +85°C

8 SO

Adjustable

Typical Operating Circuits continued at end of data sheet.