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SD4957
POWERED DEVICE(PD) AND DC/DC CONTROLLER COMPATIBLE WITH IEEE 802.3AF/AT STANDARD

    SD4957 is an Ethernet powered device and DC/DC controller IC compatible with IEEE 802.3af/at standard. The DC-DC controller supports 7.5-70V wide-range input, and the PD controller part provides functions such as detection, grading and inrush current limiting for the receiving equipment in the power over Ethernet power supply system (PoE). SD4957 integrates a 100V power MOSFET with on-resistance of 0.55Ω, and features built-in current limit, undervoltage protection and over temperature protection.

    The DC/DC controller supports SSR flyback, active clamp forward topology, and PSR flyback. It provides accurate constant voltage control loop with high system efficiency and good EMI characteristics.


Main feature
  • PD controller

  • Complete power interface based on IEEE 802.3af/at powered devices

  • 100V,0.22Ω On-chip MOSFET

  • Undervoltage lockout

  • Over temperature protection

  • 120mA inrush current limit

  • Fault automatic retry

  • Support for auxiliary power supply 

  • Delay output of PG signal after inrush current limitation has ceased

  • T2P function

  • DC/DC controller

  • Support for active clamped forward topology

  • Support for SSR flyback synchronous rectification

  • Support for PSR flyback

  • Built-in high voltage start-up

  • Integrated error amplifier

  • Maximum duty cycle limitation

  • Soft startup

  • FB over voltage protection

  • VCC undervoltage protection

  • Over temperature protection (external NTC resistor)

  • Over load protection

  • Cycle-by-cycle current limit

  • Feedback loop open-circuit protection

  • External input undervoltage protection

  • Maintenance Performance System (MPS functionality), supporting ultra-low power standby mode


Ordering Information
Product Name Package form Marking Hazardous Substance Control Packing Type Remarks
SD4957TR QFN-28-4×5×0.75-0.5 SD4957 Halogen free Tape&Reel
SD4957 QFN-28-4×5×0.75-0.5 SD4957 Halogen free Tray
Documents
title Types of Size (KB) date Download the latest English version
SD4957 0 2025-11-20 SD4957 Brief Datasheet