MAX5974E

PRODUCTION

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

Part Models
2
1ku List Price
Starting From $0.98
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Part Details

  • 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
MAX5974E
Current-Mode PWM Controllers for Low-Cost Flyback Supplies
MAX5974E/MAX5974F Block Diagram MAX5974E/MAX5974F Circuit Diagram MAX5974E/MAX5974F Pin Configuration
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Evaluation Kits

MAX5974EEVKIT

Evaluation Kit for the MAX5974E

Features and 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

Product Details

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

eval board
EVAL-LTC9105-AZ

EVAL-LTC9105-AZ: LTC9105, MAX5974C, LT4321, and ADuM1252 IEEE 802.3bt Powered Device with I2C Telemetry

Features and Benefits

  • IEEE 802.3bt-compliant Class 6 PD
  • Port telemetry with an isolated I2C interface
  • 5V/9.2A isolated synchronous forward converter

Product Details

The EVAL-LTC9105-AZ is an IEEE 802.3bt-compliant Type 3, Class 6 Power over Ethernet (PoE) powered device (PD) with port telemetry via I2C. The evaluation board features the LTC9105 PD interface controller, MAX5974C switching regulator controller, the LT4321 PoE ideal diode bridge controller, and the ADuM1252 I2C isolator.

The LTC9105 provides IEEE 802.3af-, IEEE 802.3at-, and IEEE 802.3bt-compliant interfacing with port voltage and current telemetry via I2C. It utilizes an external, low channel resistance, RDS(ON) (34mΩ typical), N-channel, hot-swap metal-oxide semiconductor, field-effect transistor (MOSFET), and 50mΩ sense resistor. Automatic maintain power signature (MPS) keeps the port connected when the current drops to a low level.

The MAX5974C controls a DC/DC converter utilizing a highly efficient active-clamp forward converter topology with synchronous rectification and provides an isolated 5V/9.2A output. The LT4321 controls eight low RDS(ON) (57mΩ typical), N-channel MOSFETs to further improve end-to-end power delivery efficiency and ease thermal design. The ADuM1252 isolates I2C data between the LTC9105 and a host controller on a nonisolated ground domain.

The EVAL-LTC9105-AZ is configured as a Class 6 PD and accepts up to 51W of delivered power from a power sourcing equipment (PSE) via its RJ45 connector (J1). The EVAL-LTC9105-AZ can be powered by a local 55V DC power supply using the auxiliary supply input terminals. With the DC590B I2C interface board connected to the EVAL-LTC9105-AZ, the EVAL-LTC9105-AZ graphical user interface (GUI) displays port telemetry and configuration options.

MAX5974EEVKIT
Evaluation Kit for the MAX5974E
EVAL-LTC9105-AZ
EVAL-LTC9105-AZ: LTC9105, MAX5974C, LT4321, and ADuM1252 IEEE 802.3bt Powered Device with I2C Telemetry
EVAL-LTC9105-AZ Board Photo Angle View EVAL-LTC9105-AZ Board Photo Top View EVAL-LTC9105-AZ Board Photo Bottom View EA PoE PD 6

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