General Description

The MAX5941A/MAX5941B integrate a complete power

IC for powered devices (PD) in a power-over-ethernet

(PoE) system. The MAX5941A/MAX5941B provide a PD

interface and a compact DC-DC PWM controller suitable

for flyback and forward converters in either isolated or

nonisolated designs.

The MAX5941A/MAX5941B PD interface complies with

the IEEE 802.3af standard, providing the PD with a detec-

tion signature, a classification signature, and an integrat-

ed isolation switch with programmable inrush current

control. These devices also feature power-mode under-

voltage lockout (UVLO) with wide hysteresis and power-

good status outputs.

The MAX5941A/MAX5941B also integrate all the building

blocks necessary for implementing DC-DC fixed-

frequency isolated power supplies. These devices are a

current-mode controller with an integrated high startup

circuit suitable for isolated telecom/industrial voltage-

range power supplies. A high-voltage startup circuit

allows the PWM controller to draw power directly from the

18V to 67V input supply during startup. The switching fre-

quency is internally trimmed to 275kHz ±10%, thus

reducing magnetics and filter components. The

MAX5941A allows an 85% operating duty cycle and can

be used to implement flyback converters. The MAX5941B

limits the operating duty cycle to less than 50% and can

be used in single-ended forward converters. The

MAX5941A/MAX5941B are designed to work with or with-

out an external diode bridge in front of the PD.

The MAX5941A/MAX5941B are available in 16-pin SO

packages.

Applications

IP Phones

Wireless Access Nodes

Internet Appliances

Computer Telephony

Security Cameras

Power Devices in Power-Over-Ethernet/

Power-Over-MDI

Features

o Powered Device Interface

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

Gate Output Allows External Control of the

Internal Isolation FET

Programmable Inrush Current Control

Programmable Undervoltage Lockout

o PWM Controller

Wide Input Range: 18V to 67V

Current-Mode Control

Leading-Edge Blanking

Internally Trimmed 275kHz ±10% Oscillator

Soft-Start

IEEE 802.3af-Compliant Power-Over-Ethernet

Interface/PWM Controller for Power Devices

________________________________________________________________ Maxim Integrated Products

1

Ordering Information

19-3069; Rev 4; 6/06

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.

PART

TEMP RANGE

PIN-

PACKAGE

MAX DUTY

CYCLE (%)

MAX5941AESE -40°C to +85°C 16 SO (S16M-6)

85

MAX5941ACSE

0°C to +70°C 16 SO (S16M-6)

85

MAX5941BESE -40°C to +85°C 16 SO (S16M-6)

50

MAX5941BCSE

0°C to +70°C 16 SO (S16M-6)

50

Typical Operating Circuit appears at end of data sheet.

16

15

14

13

12

11

10

9

1

2

3

4

5

6

7

8

V+

NDRV

V-

CS

GND

PGOOD

PGOOD

OUT

TOP VIEW

MAX5941A

MAX5941B

SO

OPTO

RCL

SS_SHDN

ULVO

GATE

Pin Configuration

EVALUATION

KIT

AVAILABLE