MAX5974E

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

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Overview

Features and Benefits
Product Details

Features and Benefits

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

Product Details

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.

Applications

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

Product Categories

Power Monitor, Control, and Protection
- PoE Powered Device (PD)

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Product Lifecycle Production

At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.

Evaluation Kits (1)

MAX5974EEVKIT

Evaluation Kit for the MAX5974E

MAX5974EEVKIT

View Detailed Evaluation Kit Information

The MAX5974E evaluation kit (EV kit) is a fully assembled and tested surface-mount circuit board featuring the MAX5974E spread-spectrum, current-mode PWM controller for Power-over-Ethernet (PoE) powered device (PD) applications. The EV kit circuit is a nonisolated, compact, and low-cost design used in Power-over-LAN (PoLAN) applications requiring DC power from an Ethernet network port for PDs such as IP phones, wireless access nodes, and security cameras.

The EV kit features a Class 2 PD with a 200kHz switching frequency flyback DC-DC converter using the IC. The circuit achieves high efficiency up to 91% using a synchronous rectifier. The surface-mount transformer provides energy storage for the output, which is configured for +3.3V and provides up to 1.8A load current.

The EV kit includes the MAX5969B IEEE® 802.3af/at-compliant PD interface-controller IC that provides PD detection signature, PD classification signature, inrush current control, undervoltage lockout (UVLO), and current limit after the PD is on.

The EV kit circuit receives its power from IEEE 802.3af/at-compliant power-sourcing equipment (PSE). The PSE provides the required -39V to -57V DC power over a twisted-pair Ethernet network cable to the EV kit's RJ45 MagJack®. The EV kit features a 1 x 1Gb RJ45 MagJack and two full-bridge diodes for separating the DC power provided by an endspan or midspan Ethernet system.

The EV kit circuit can also be powered by a +39V to +57V wall-adapter power source applied at the WAD_IN and WAD_GND PCB pads. When a wall-adapter power source is detected, it always takes precedence over the PSE source, allowing the wall adapter to power the EV kit.

Warning: The EV kit is designed to operate with high voltages. Dangerous voltages are present on this EV kit and on equipment connected to it. Users who power up this EV kit or power the sources connected to it must be careful to follow safety procedures appropriately to work with high-voltage electrical equipment.

Under severe fault or failure conditions, this EV kit may dissipate large amounts of power, which could result in the mechanical ejection of a component or of component debris at high velocity. Operate this kit with care to avoid possible personal injury.

Applications

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

Features & Benefits

IEEE 802.3af/at-Compliant PD Interface Circuit
-39V to -57V Startup Input Voltage Range
91% Efficiency (at VIN = +48V)
Nonisolated +3.3V Output at 1.8A
PD Detection and Configurable Classification Signatures
2-Event Classification and Wall-Adapter Detect Output
Inrush Current Limit of 180mA (max)
Internal UVLO at -38.6V
Evaluates Endspan and Midspan Ethernet Systems
Simplified Wall-Adapter Interface
Proven PCB Layout
Fully Assembled and Tested

Documentation & Resources

Data Sheets

MAX5974E-MAX5974F: Current-Mode PWM Controllers for Low-Cost Flyback Supplies Data Sheet (Rev. 2)
11/26/2013
PDF

Reliability Data

MAX5974E Reliability Data
1/12/2023
PDF

Design Resources

ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.View our quality and reliability program and certifications for more information.

Part Number	Material Declaration	Reliability Data	Pin/Package Drawing	CAD Symbols, Footprints & 3D Models
MAX5974EETE+	Material Declaration	Reliability Data	Thin Quad Flatpack, No Leads	Ultra Librarian SamacSys
MAX5974EETE+T	Material Declaration	Reliability Data	Thin Quad Flatpack, No Leads	Ultra Librarian SamacSys
Wafer Fabrication Data		MAX5974E Reliability Data

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Evaluation Boards

Pricing displayed is based on 1-piece.

Up to two boards can be purchased through Analog.com. To order more than two, please purchase through one of our listed distributors.

Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.