MAX8709B Просмотр технического описания (PDF) - Maxim Integrated

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MAX8709B

High-Efficiency CCFL Backlight Controller with SMBus Interface

Maxim Integrated 

19-0768; Rev 0; 3/07

High-Efficiency CCFL Backlight

Controller with SMBus Interface

General Description

The MAX8709B integrated backlight controller is

optimized to drive cold-cathode fluorescent lamps

(CCFLs) using a resonant full-bridge inverter architecture.

The resonant operation maximizes striking capability and

provides near-sinusoidal waveforms over the entire input

range to improve CCFL lifetime. The controller operates

over a wide input voltage range of 4.6V to 28V with high

power-to-light efficiency. The device also includes safety

features that effectively protect against many single-point

fault conditions including lamp-out and short-circuit faults.

The MAX8709B achieves 10:1 dimming range by “chop-

ping” the lamp current on and off using a digital pulse-

width-modulation (DPWM) method. The minimum DPWM

duty cycle of the MAX8709B is 12.5%. The brightness is

controlled with a 2-wire SMBus™-compatible interface.

The device directly drives the four external N-channel

power MOSFETs of the full-bridge inverter. An internal

5.3V linear regulator powers the MOSFET drivers, the

DPWM oscillator, and most of the internal circuitry. The

MAX8709B is available in a space-saving 28-pin

thin QFN package and operates over a -40°C to +85°C

temperature range.

Applications

Notebook Computer Displays LCD TVs

LCD Monitors

Automotive Displays

SMBus is a trademark of Intel Corp.

VIN

BATT

VCC

GND

VDD

BST2

LOT

BST1

REF

GH1

MAX8709B

LX1

ILIM

LX2

GL1

CCV

PGND

CCI

GL2

GH2

SUS

VFB

SDA

ISEC

SCL

IFB

Features

♦ Synchronized to Resonant Frequency

Longer Lamp Life

Guaranteed Striking Capability

High Power-to-Light Efficiency

♦ Wide Input Voltage Range (4.6V to 28V)

♦ Feed Forward for Excellent Line Rejection

♦ SMBus Dimming Control Interface

♦ 10:1 Dimming Range

♦ Guaranteed 200Hz to 220Hz DPWM Frequency

♦ Secondary Voltage Limit Reduces Transformer

Stress

♦ Adjustable Lamp-Out Protection with 1s Timer

♦ Secondary Current Limit Protects Against High-

Voltage Short Circuits to Ground

♦ Small, 5mm x 5mm, Thin QFN Package

PART

MAX8709BETI

Ordering Information

TEMP RANGE PIN-PACKAGE

-40°C to +85°C 28 Thin QFN 5mm x 5mm

Pin Configuration appears at end of data sheet.

Minimal Operating Circuit

________________________________________________________________ Maxim Integrated Products 1

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

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