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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

Product Details

Key Features

Parametric specs for Powered Devices
Compliance IEEE 802.3af
RDS(ON) (Ω) (PD MOSFET) 0.6
PWM No
Package/Pins See Data Sheet
Oper. Temp. (°C) -40 to +85
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Simplified Block Diagram

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Parameters

Parametric specs for Powered Devices
Compliance IEEE 802.3af
RDS(ON) (Ω) (PD MOSFET) 0.6
PWM No
Package/Pins See Data Sheet
Oper. Temp. (°C) -40 to +85

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

Applications/Uses

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

Description

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.

Simplified Block Diagram

MAX5940, MAX5940A, MAX5940B: Pin Configuration MAX5940, MAX5940A, MAX5940B: Pin Configuration Zoom icon

Technical Docs

Support & Training

Search our knowledge base for answers to your technical questions.

Filtered Search

Our dedicated team of Applications Engineers are also available to answer your technical questions. Visit our support portal .