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MAX5953A, MAX5953B, MAX5953C, MAX5953D

IEEE 802.3af PD Interface and PWM Controllers with Integrated Power MOSFETs

Product Details

Key Features

Simplified Block Diagram

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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 MOSFET
    • Programmable Inrush Current Control
    • Programmable Undervoltage Lockout (MAX5953A/MAX5953C)
  • DC-DC Converter
    • Clamped, Two-Switch Power IC for High Efficiency
    • Integrated High-Voltage 0.4Ω Power MOSFETs Up to 15W Output Power
    • Bias Voltage Regulator with Automatic High-Voltage Supply Turn-Off
    • 11V to 76V Wide Input Voltage Range
    • Feed-Forward Voltage-Mode Control for Fast Input Transient Rejection
    • Programmable Undervoltage Lockout
    • Overtemperature Shutdown
    • Indefinite Short-Circuit Protection with Programmable Fault Integration
    • Integrated Look-Ahead Signal for Secondary-Side Synchronous Rectification
    • > 90% Efficiency with Synchronous Rectification
    • Up to 500kHz Switching Frequency
  • High-Power (2.22W), 7mm x 7mm Thermally Enhanced Lead-Free Thin QFN Package

Applications/Uses

  • Computer Telephony
  • IEEE 802.3af Powered Devices
  • Internet Appliances
  • IP Phones
  • Security Cameras
  • Wireless Access Nodes

Description

The MAX5953A/MAX5953B/MAX5953C/MAX5953D integrate a complete power IC solution for Powered Devices (PD) in a Power-Over-Ethernet (PoE) system, in compliance with the IEEE 802.3af standard. The MAX5953A/MAX5953B/MAX5953C/MAX5953D provide the PD with a detection signature, a classification signature, and an integrated isolation switch with programmable inrush current control. These devices also integrate a voltage-mode PWM controller with two power MOSFETs connected in a two-switch voltage-clamped DC-DC converter configuration.

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 devices feature power-mode undervoltage lockout (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 MAX5953A/MAX5953C have an adjustable UVLO threshold with the default value compliant to the 802.3af standard, while the MAX5953B/MAX5953D have a lower and fixed UVLO threshold compatible with some legacy pre-802.3af power-sourcing equipment (PSE) devices.

The DC-DC converters are operable in either forward or flyback configurations with a wide input voltage range from 11V to 76V and up to 15W of output power. The voltage-clamped power topology enables full recovery of stored magnetizing and leakage inductive energy for enhanced efficiency and reliability. When using the high-side MOSFET, the controller can be configured as a buck converter. A look-ahead signal for driving secondary-side synchronous rectifiers can be used to increase efficiency. A wide array of protection features include UVLO, over-temperature shutdown, and short-circuit protection with hiccup current limit for enhanced performance and reliability. Operation up to 500kHz allows for smaller external magnetics and capacitors.

The MAX5953A/MAX5953B/MAX5953C/MAX5953D are available in a high-power (2.22W), 7mm x 7mm thermally enhanced thin QFN package.

Simplified Block Diagram

MAX5953A, MAX5953B, MAX5953C, MAX5953D: Typical Operating Circuit MAX5953A, MAX5953B, MAX5953C, MAX5953D: 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 .