MAX8729 Maxim Integrated Products, MAX8729 Datasheet

MAX8729

Manufacturer Part Number

MAX8729

Description

Constant-Frequency / Half-Bridge CCFL Inverter Controller

Manufacturer

Maxim Integrated Products

Datasheet

1.MAX8729.pdf (26 pages)

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The MAX8729 cold-cathode-fluorescent lamp (CCFL)

inverter controller is designed to drive multiple CCFLs

using the half-bridge inverter consisting of two external

n-channel power MOSFETs. The half-bridge topology

minimizes the component count, while providing near

sinusoidal drive waveforms. The MAX8729 operates in

resonant mode during striking and switches over to con-

stant-frequency operation after all the lamps are lit. This

unique feature ensures reliable striking under all condi-

tions and reduces the transformer stress.

The MAX8729 provides accurate lamp-current regulation

(±2.5%). The lamp current is adjustable with an external

resistor. The MAX8729 changes the brightness by turning

the CCFL on and off using a digital pulse-width modula-

tion (DPWM) method, while maintaining the lamp current

constant. The brightness can be adjusted with an analog

voltage on the CNTL pin, or with an external PWM signal.

The MAX8729 is capable of synchronizing and adjusting

the phase of the gate drivers and DPWM oscillator. These

features allow multiple MAX8729 ICs to be connected in a

daisy-chain configuration. The switching frequency and

DPWM frequency of the master IC can be easily adjusted

using external resistors, or synchronized with system sig-

nals. If the controller loses the external sync signals, it

switches over to the internal oscillators and keeps operat-

ing. Phase-shift select pins PS1 and PS2 can be used to

program four different phase shifts, allowing up to five

MAX8729s to be used together.

The MAX8729 protects the inverter from lamp-out, sec-

ondary overvoltage, and secondary short-circuit faults.

The MAX8729 can drive large-power MOSFETs typically

used in applications where one power stage drives four

or more CCFL tubes in parallel. An internal 5.35V linear

regulator powers the MOSFET drivers and most of the

internal circuitry. The MAX8729 is available in a low-cost,

28-pin QSOP package and operates over the -40°C to

+85°C extended temperature range.

LCD Monitors

LCD TVs

19-3754; Rev 0; 8/05

Pin Configuration appears at end of data sheet.

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.

MAX8729EEI

PART

________________________________________________________________ Maxim Integrated Products

-40°C to +85°C

Ordering Information

TEMP RANGE

Notebook Computers

Automotive Infotainment

Constant-Frequency, Half-Bridge CCFL

General Description

Applications

PIN-PACKAGE

28 QSOP

♦ Low-Cost, Half-Bridge Inverter Topology

♦ Resonant Mode Striking Ensures Startup

♦ Constant-Frequency Operation After Lamp

♦ Drives Large External MOSFETs

♦ Supports Multilamp Applications

♦ Sync and Phase-Shift Controls Allow Daisy-

♦ Adjustable Switching Frequency and DPWM

♦ ±2.5% Lamp-Current Regulation

♦ 10:1 Dimming Range

♦ Accurate Analog-Dimming Control

♦ Lamp-Out Detection with Adjustable Timeout

♦ Secondary Current and Voltage Limiting

♦ Primary Current Limit with R

♦ Adjustable DPWM Rise and Fall Time

♦ Low-Cost, 28-Pin QSOP Package

Ignition

Chained Operation

Frequency

DIMMING

ON/OFF

INPUT

VCC

Inverter Controller

Simplified Operating Circuit

GND

SHDN

CNTL

SEL

PSCK

PS1

PS2

DPWM

HFCK

LFCK

MAX8729

PCOMP

HSYNC

LSYNC

COMP

PGND

ISEC

TFLT

BST

VFB

IFB

VCC

DS(ON)

Sensing

Features

CCFL

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