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Low-Cost, SMBus, CCFL Backlight Controller

Integrated Backlight Controller Optimized to Drive CCFLs Using Resonant Full-Bridge Inverter Architecture

Product Details

Key Features

Simplified Block Diagram

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Key Features

  • Accurate Dimming Control Using SMBus, PWM Interface, or Ambient Light Sensor
  • 10:1 Dimming Range with 256-Step Resolution
  • Resonant-Mode Operation
    • Longer Lamp Life with Near Sinusoidal Lamp-Current Waveform
    • Guaranteed Striking Capability
    • High-Power-to-Light Efficiency
  • Wide Input-Voltage Range (4.5V to 28V)
  • Input Feed-Forward for Excellent Line Rejection
  • ±2.5% Lamp-Current Regulation
  • Adjustable 1.5% Accurate DPWM Frequency
  • Dual Lamp-Current Feedback Inputs
  • Comprehensive Fault Protection
    • Secondary Voltage Limiting
    • Primary Current Limit with Lossless Sensing
    • Lamp-Out Protection with Adjustable Timeout
    • Secondary Short-Circuit Protection
  • Small 28-Pin, 5mm x 5mm, Thin QFN Package

Applications/Uses

  • LCD Monitors
  • Notebooks

Description

The MAX8759 integrated cold-cathode fluorescent lamp (CCFL) inverter controller is designed to drive CCFLs using a full-bridge resonant inverter. The resonant operation ensures reliable striking and provides near-sinusoidal waveforms over the entire input range. The controller operates over a wide input-voltage range of 4.5V to 28V with high power to light efficiency. The device also includes safety features that effectively protect against single-point fault conditions such as lamp-out, secondary overvoltage, and secondary short-circuit faults.

The MAX8759 provides accurate lamp-current regulation (±2.5%) for superior CCFL inverter performance. The lamp current is adjustable with an external resistor; 10:1 dimming range can be achieved by turning the CCFL on and off using a digital pulse-width modulation (DPWM) method, while maintaining the lamp-current constant. The MAX8759 provides three mechanisms for controlling brightness: 2-wire SMBus™-compatible interface, external ambient-light sensor (ALS), or system PWM control. The MAX8759 supports Intel display power-saving technology (DPST) to maximize battery life. The device includes two lamp-current feedback input pins that support dual-lamp applications with a minimum number of external components.

The MAX8759 controls a full-bridge inverter for maximum efficiency and directly drives four external n-channel power MOSFETs. An internal 5.35V linear regulator powers the MOSFET drivers and most of the internal circuitry. The MAX8759 is available in a space-saving, 28-pin, thin QFN package and operates over a -40°C to +85°C temperature range.

Simplified Block Diagram

MAX8759: Minimal Operating Circuit MAX8759: Minimal 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 .