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Current-Mode PWM Controllers for Low-Cost Flyback Supplies

IEEE 802.3af/at-Compliant, Powered Device PWM Controllers for High-Efficiency Nonisolated DC-DC Converters

Product Details

Key Features

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Simplified Block Diagram

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Parameters

Key Features

  • Peak Current-Mode Control, Synchronous Flyback PWM Controller
  • Synchronous MOSFET Driver Output
  • Internal 1% Error Amplifier Eliminates Shunt Regulator and Optocoupler
  • 100kHz to 600kHz Programmable ±8% Switching Frequency, Synchronization Up to 1.2MHz
  • Programmable Frequency Dithering for Low-EMI, Spread-Spectrum Operation
  • Programmable Dead Time, PWM Soft-Start, Current Slope Compensation
  • Programmable Feed-Forward Maximum Duty-Cycle Clamp, 80% Maximum Limit
  • Frequency Foldback for High-Efficiency Light-Load Operation
  • Internal Bootstrap UVLO with Large Hysteresis
  • 100µA (typ) Startup Supply Current
  • Fast Cycle-by-Cycle Peak Current-Limit, 35ns Typical Propagation Delay
  • 115ns Current-Sense Internal Leading-Edge Blanking
  • Output Short-Circuit Protection with Hiccup Mode
  • Internal 18V Zero Clamp on Supply Input
  • 3mm x 3mm, Lead-Free, 16-Pin TQFN-EP

Applications/Uses

  • High-Power PD (Beyond the 802.3af/at Standard)
  • IP Phones
  • PoE IEEE® 802.3af/at Powered Devices
  • Security Cameras
  • Wireless Access Nodes

Description

The MAX5974E/MAX5974F provide control for wide-input-voltage, current-mode PWM, nonisolated, synchronous flyback converters in Power-over-Ethernet (PoE) powered device (PD) applications. The MAX5974E is well-suited for universal or telecom input range, while the MAX5974F also accommodates low input voltage down to 8.4V.

The devices include several features to enhance supply efficiency, including a synchronous MOSFET driver output. The AUX driver drives an output synchronous rectifier to lower conduction losses. Programmable dead time between the AUX and main driver allows for zero-voltage switching (ZVS). Under light load conditions, the devices reduce the switching frequency (frequency foldback) to reduce switching losses.

An internal error amplifier with a 1% reference eliminates the need for an external shunt regulator and optocoupler.

The programmable frequency dithering feature provides low-EMI, spread-spectrum operation.

The MAX5974E/MAX5974F are available in 16-pin TQFN-EP packages and are rated for operation over the -40°C to +85°C temperature range.

Simplified Block Diagram

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.