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MAX5941A, MAX5941B

IEEE 802.3af-Compliant Power-Over-Ethernet Interface/PWM Controller for Power Devices

Industry's First Fully Integrated IEEE 802.3af-Compliant Power-over-Ethernet Power-Supply ICs
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Active: In Production.


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 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 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 frequency 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 without an external diode bridge in front of the PD.

The MAX5941A/MAX5941B are available in 16-pin SO packages.

Data Sheet

Download this datasheet in PDF formatDownload Rev 4 (PDF, 380kB)
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An evaluation board is available: MAX5941BEVKIT

Key Features

  • 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
  • PWM Controller
    • Wide Input Range: 18V to 67V
    • Current-Mode Control
    • Leading-Edge Blanking
    • Internally Trimmed 275kHz ±10% Oscillator
    • Soft-Start


  • Computer Telephony
  • Internet Appliances
  • IP Phones
  • Power Devices in Power-Over-Ethernet/Power-Over-MDI
  • Security Cameras
  • Wireless Access Nodes

Key Specifications:

Powered Devices
Part Number IEEE Compliance RDS(ON)
Protection Features Prog. UVLO Oper. Temp.
MAX5941  802.3af 0.6 Yes 275 Programmable Inrush Current Yes -40 to +85 $3.34 @1k
See All Powered Devices (21)

Pricing Notes:

This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.


MAX5941A, MAX5941B: Typical Operating Circuit
Typical Operating Circuit

More Information

New Product Press Release   2004-01-06 ]

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Information Index

Document Ref.: 19-3069 Rev 4; 2006-06-29
This page last modified: 2007-08-22