Rainbow-electronics MAX8709 User Manual download pdf

General Description

The MAX8709 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 fea-

tures that effectively protect against many single-point

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

The MAX8709 achieves 10:1 dimming range by “chop-

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

width-modulation (DPWM) method. 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

MAX8709 is available in a space-saving 28-pin thin QFN

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

erature range.

Applications

Notebook Computer Displays LCD TVs

LCD Monitors Automotive Displays

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

MAX8709

High-Efficiency CCFL Backlight

Controller with SMBus Interface

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

SCL

SDA

SUS

CCI

CCV

BATT

GND

LOT

REF

ILIM

V

CC

V

DD

BST2

BST1

GH1

LX1

LX2

GL1

PGND

GL2

GH2

VFB

ISEC

IFB

MAX8709

V

IN

Minimal Operating Circuit

19-3177; Rev 0; 1/04

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.

EVALUATION KIT

AVAILABLE

PART

TEMP RANGE

PIN-PACKAGE

MAX8709ETI

-40°C to +85°C

28 Thin QFN 5mm x 5mm

SMBus is a trademark of Intel Corp.

Pin Configuration appears at end of data sheet.

1 2 3 4 5 6 ... 22 23

Summary of Contents

Page 1 - Minimal Operating Circuit

General DescriptionThe MAX8709 integrated backlight controller is optimizedto drive cold-cathode fluorescent lamps (CCFLs) using aresonant full-bridge

Page 2 - ELECTRICAL CHARACTERISTICS

MAX8709High-Efficiency CCFL Backlight Controller with SMBus Interface10 ______________________________________________________________________________

Page 3

MAX8709High-Efficiency CCFL Backlight Controller with SMBus Interface_________________________________________________________________________________

Page 4

MAX8709High-Efficiency CCFL Backlight Controller with SMBus Interface12 ______________________________________________________________________________

Page 5 - MAX8709 toc03

MAX8709High-Efficiency CCFL Backlight Controller with SMBus Interface_________________________________________________________________________________

Page 6 - DPWM OPERATION (10%)

MAX8709High-Efficiency CCFL Backlight Controller with SMBus Interface14 ______________________________________________________________________________

Page 7

MAX8709High-Efficiency CCFL Backlight Controller with SMBus Interface_________________________________________________________________________________

Page 8 - Pin Description

MAX8709High-Efficiency CCFL Backlight Controller with SMBus Interface16 ______________________________________________________________________________

Page 9 - Pin Description (continued)

MAX8709High-Efficiency CCFL Backlight Controller with SMBus Interface_________________________________________________________________________________

Page 10

MAX8709High-Efficiency CCFL Backlight Controller with SMBus Interface18 ______________________________________________________________________________

Page 11 - Detailed Description

MAX8709High-Efficiency CCFL Backlight Controller with SMBus Interface_________________________________________________________________________________

Page 12 - Figure 3. Resonant Operation

MAX8709High-Efficiency CCFL Backlight Controller with SMBus Interface2 _______________________________________________________________________________

Page 13 - (CCI, CCV)

MAX8709High-Efficiency CCFL Backlight Controller with SMBus Interface20 ______________________________________________________________________________

Page 14 - DPWM Dimming Control

MAX8709High-Efficiency CCFL Backlight Controller with SMBus Interface_________________________________________________________________________________

Page 15 - DPWM SETTINGS

MAX8709High-Efficiency CCFL Backlight Controller with SMBus Interface22 ______________________________________________________________________________

Page 16 - SMBus Interface (SDA, SCL)

MAX8709High-Efficiency CCFL Backlight Controller with SMBus InterfaceMaxim cannot assume responsibility for use of any circuitry other than circuitry

Page 17 - Figure 9. SMBus Read Timing

MAX8709High-Efficiency CCFL Backlight Controller with SMBus Interface_________________________________________________________________________________

Page 18 - Table 3. Commands Description

MAX8709High-Efficiency CCFL Backlight Controller with SMBus Interface4 _______________________________________________________________________________

Page 19 - Applications Information

MAX8709High-Efficiency CCFL Backlight Controller with SMBus Interface_________________________________________________________________________________

Page 20 - Component Selection

LAMP-OUT VOLTAGELIMITING AND TIMEOUTMAX8709 toc09A: VVFB, 1V/divB: VIFB, 1V/div0V0VAB200ms/divMAX8709High-Efficiency CCFL Backlight Controller with SM

Page 21 - Table 7. CCFL Specifications

MAX8709High-Efficiency CCFL Backlight Controller with SMBus Interface_________________________________________________________________________________

Page 22 - Pin Configuration

MAX8709High-Efficiency CCFL Backlight Controller with SMBus Interface8 _______________________________________________________________________________

Page 23 - Package Information

MAX8709High-Efficiency CCFL Backlight Controller with SMBus Interface_________________________________________________________________________________

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