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

Product Details

Key Features

Parametric specs for Powered Devices
Compliance IEEE 802.3af
RDS(ON) (Ω) (PD MOSFET) 0.6
PWM Yes
Switching Frequency (kHz) 275
Package/Pins SOIC (N) HYBRID/16
Oper. Temp. (°C) -40 to +85
Budgetary
Price (See Notes)
3.99
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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 Yes
Switching Frequency (kHz) 275
Package/Pins SOIC (N) HYBRID/16
Oper. Temp. (°C) -40 to +85
Budgetary
Price (See Notes)
3.99

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/ULVO
    • PGOOD/Active-Low PGOOD Outputs Enable PWM Controller
  • PWM Controller
    • Wide Input Range: 18V to 67V
    • Isolated (Without Optocoupler) or Nonisolated Power Supply
    • Current-Mode Control
    • Leading-Edge Blanking
    • Internally Trimmed 275kHz ±10% Oscillator
    • Soft-Start

Applications/Uses

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

Description

The MAX5942A/MAX5942B integrate a complete power IC for powered devices (PD) in a power-over-ethernet (PoE) system. The MAX5942A/MAX5942B provide a PD interface and a compact DC-DC PWM controller suitable for flyback and forward converters in either isolated or nonisolated designs.

The MAX5942A/MAX5942B 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 MAX5942A/MAX5942B also integrate all the building blocks necessary for implementing DC-DC fixed-frequency isolated power supplies. This device is 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 MAX5942A allows an 85% operating duty cycle and can be used to implement flyback converters. The MAX5942B limits the operating duty cycle to less than 50% and can be used in single-ended forward converters. The MAX5942A/MAX5942B are designed to work with or without an external diode bridge in front of the PD.

The MAX5942A/MAX5942B are available in 16-pin SO packages.

Simplified Block Diagram

MAX5942A, MAX5942B: Typical Operating Circuit MAX5942A, MAX5942B: Typical Operating Circuit 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 .

Sampling:
Selecting the Sample button above will redirect to the third-party ADI Sample Site. The part selected will carry over to your cart on this site once logged in. Please create a new account there if you have never used the site before. Contact SampleSupport@analog.com with any questions regarding this Sample Site.