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MAX5940, MAX5940A, MAX5940B

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
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Status Explanations for product status codes

Active: In Production.


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.

Data Sheet

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An evaluation board is available: MAX5940BEVKIT

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


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

Key Specifications:

Powered Devices
Part Number IEEE Compliance RDS(ON)
PWM Protection Features Prog. UVLO Oper. Temp.
MAX5940  802.3af 0.6 No Programmable Inrush Current Yes -40 to +85 $1.37 @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.


MAX5940, MAX5940A, MAX5940B: Pin Configuration
Pin Configuration

More Information

New Product Press Release   2003-11-11 ]

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Information Index

Document Ref.: 19-2991 Rev 2; 2006-03-27
This page last modified: 2009-10-12