MAX5940D

PRODUCTION

IEEE 802.3af PD Interface Controller for Power-Over-Ethernet

Industry's First IEEE 802.3af-Compliant Power-Device Interface Controllers with Adjustable Undervoltage Lockout

Data Sheet (Rev. 2) Product Selection Table

Viewing:

Overview

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/Active-Low PGOOD Outputs to Enable Downstream DC-DC Converters
-40°C to +85°C Operating Temperature Range

The MAX5940A/MAX5940B/MAX5940C/MAX5940D provide 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 maximum rating of 90V.

An integrated MOSFET provides PD isolation during detection and classification. All devices guarantee a leakage 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, classification, 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 (active-low PGOOD) outputs and have an adjustable UVLO threshold with the default value compliant 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

Computer Telephony
IP Phones Security Cameras
Wireless Access Nodes IEEE 802.3af Power Devices

Documentation

Data Sheet 1

MAX5940-MAX5940B: IEEE 802.3af PD Interface Controller for Power-Over-Ethernet Data Sheet (Rev.2) 03/27/2006

This is the most up-to-date revision of the Data Sheet.

Software Resources

Can't find the software or driver you need?

Request a Driver/Software

Evaluation Kits

Evaluation Kit for the MAX5940B and MAX5940D

Buy Now View Details

Features and Benefits

IEEE 802.3af-Compliant PD Interface Circuit
PD Detection and Configurable Classification Signatures
Programmable Inrush Current Limit
Programmable UVLO
Isolated 6W Flyback DC-DC Converter
-36V to -60V Input Range
Isolated 4.25V Output at 1.4A
Evaluates Endspan and Midspan Ethernet Systems
Interface to an External DC-DC Converter
Local Power Inputs (Wall Cube)
Also Evaluates MAX5940D (IC Replacement Required)
Fully Assembled and Tested

Product Details

The MAX5940B evaluation kit (EV kit) is a fully assembled and tested surface-mount circuit board featuring an Ethernet port, network powered device (PD) interface controller circuit for -48V supply systems. The EV kit uses the MAX5940B IEEE® 802.3af-compliant network PD interface controller in an 8-pin SO package. The MAX5940B EV kit can also evaluate the MAX5940D rated for an absolute maximum input voltage of 90V. The MAX5940B features an internal isolation switch that limits inrush current. The MAX5940B is used in power-over-LAN applications requiring DC power from an Ethernet network port for PDs such as IP phones, wireless access nodes, and security cameras.

The MAX5940B EV kit receives power from an IEEE 802.3af-compliant power sourcing equipment (PSE). See the MAX5922 and MAX5935 data sheets for PSE controllers. The PSE provides the required -44V to -57V DC power over an unshielded twisted-pair Ethernet network cable to the EV kit's RJ-45 jack. The EV kit features a 10/100BASE-TX Voice-over-IP (VoIP) magnetic module and two diode bridges for separating the DC power provided by an endspan or midspan Ethernet system.

The EV kit demonstrates the full functionality of the MAX5940B such as the PD detection signature, configurable PD classification signature, programmable inrush current, and undervoltage lockout (UVLO). All of these features are configurable on the EV kit and additional test points for voltage probing and interfacing have been provided for the PD interface.

The MAX5940B EV kit also features a galvanically isolated 6W, 275kHz switching frequency flyback DC-DC converter, which uses the MAX5014 current-mode PWM controller. The MAX5940B's -48V output provides power for the converter circuit. The DC-DC converter is configured for an output voltage of 4.25V and provides up to 1.4A at the output. High efficiency up to 82.2% is achieved using a single transistor flyback DC-DC converter topology. The surface-mount transformer provides 1500V galvanic isolation for the output. UVLO, soft-start, and thermal shutdown provide a robust 6W isolated power supply.

The EV kit can be reconfigured for interfacing to an external DC-DC converter for an additional 7W of output power.

Warning: The MAX5940B EV kit operates with high voltages. Dangerous voltages are present on this EV kit and on equipment connected to it. Users who power up this EV kit or power the sources connected to it must be careful to follow safety procedures appropriate to working with high-voltage electrical equipment.

Under severe fault or failure conditions, this EV kit may dissipate large amounts of power, which could result in the mechanical ejection of a component or of component debris at high velocity. Operate this EV kit with care to avoid possible personal injury.