ML4877CR MICRO-LINEAR [Micro Linear Corporation], ML4877CR Datasheet

ML4877CR

Manufacturer Part Number

ML4877CR

Description

LCD Desktop Backlight Lamp Driver

Manufacturer

MICRO-LINEAR [Micro Linear Corporation]

Datasheet

1.ML4877CR.pdf (11 pages)

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Manufacturer

Quantity

Price

Company:

Meier Automation Equipment Co., Limited

Part Number:

ML4877CR

Manufacturer:

MICROLINEAR

Quantity:

20 000

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GENERAL DESCRIPTION

The ML4877 is an ideal solution for driving multiple cold

cathode fluorescent tubes (CCFL) used in liquid crystal

display (LCD) backlight applications. It provides dimming

ballast control for the LCD display.

By utilizing differential drive the ML4877 can deliver the

same light output with significantly less input power

compared to existing single ended drive schemes.

Improvements as high as 30% can be realized when using

low power lamps and advanced LCD screen housings. This

increased light output is achieved because the differential

drive configuration is much less sensitive, and therefore

less power is wasted in the capacitive parasitics that exist

in the backlight housing. An additional benefit of this

configuration is an even distribution of light.

The IC includes an adjustable lamp out detect circuit that

latches the IC off when a lamp fault is detected. Also, the

unique architecture of the ML4877 allows the

development of a backlight system that will inherently

meet the UL requirements for safety.

The ML4877 is optimized for large LCD applications

applications where high efficiency is critical to maximize

battery life. The high efficiency is achieved by a resonant

scheme with zero voltage switching.

BLOCK DIAGRAM

ON/OFF

HVDD

VREF

PGND

REGULATOR

AZR

MASTER

LINEAR

UVLO

BIAS

VDD

GND

Q R

VDD

LCD Desktop Backlight Lamp Driver

SHOT

ONE

–

B ON

DR3

CLK

VDD

R Q

THRESHOLD

OSCILLATOR

RESONANT

DETECTOR

B OFF

DR1

FEATURES

Ideal for 30W inverter designs, 1 to 8 lamp design

PWM dimming capability

Backlight lamp driver with differential drive

Up to 30% lower power for same light output

Low standby current (<10µA)

Improved efficiency ( 95%)

Allows all N-channel MOSFET drive

Adjustable lamp out detect with latch

Resonant threshold detection and synchronous

rectification

Positive input for dimming control

* THIS PART IS END OF LIFE AS OF JULY 1, 2000

B SYNC OUT

DELAY

EDGE

DR1

NEG

–

SS CAP

DR2

–

0.5V

ML4877*

6 L ILIM

8 LEA OUT

L RTD

L GATE 1

L GATE 2

LEA–

LEA+

JULY 2000

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ML4877CR Summary of contents

Page 1

GENERAL DESCRIPTION The ML4877 is an ideal solution for driving multiple cold cathode fluorescent tubes (CCFL) used in liquid crystal display (LCD) backlight applications. It provides dimming ballast control for the LCD display. By utilizing differential drive the ML4877 can ...

Page 2

ML4877 PIN CONFIGURATION PIN DESCRIPTION PIN NAME FUNCTION 1 LEA+ Positive input for lamp error amp 2 AZR Connection to gate of external FET for high voltage regulator. Internally a zener diode to ground CAP Connection of optional ...

Page 3

ABSOLUTE MAXIMUM RATINGS Absolute maximum ratings are those values beyond which the device could be permanently damaged. Absolute maximum ratings are stress ratings only and functional device operation is not implied. Supply Current (I ) ............................................... 75mA CC Output Current, ...

Page 4

ML4877 ELECTRICAL CHARACTERISTICS SYMBOL PARAMETER DELAY TIMER Delay Time HIGH VOLTAGE INVERTER Oscillator Nominal Frequency Discharge Current Peak Voltage Valley Voltage Output Drivers Output High - L GATE 1, 2 Output Low - L GATE 1, 2 Rise & Fall ...

Page 5

ELECTRICAL CHARACTERISTICS SYMBOL PARAMETER BIAS VDD Supply Current VDD Supply Current VREF Load Regulation VREF Output Voltage VREF Line Regulation VREF Line, Load, Temp Note 1: Limits are guaranteed by 100% testing, sampling, or correlation with worst case test conditions. ...

Page 6

ML4877 5 TO 18V IN *OPTIONAL SEE NOTE AZR VDD 2 13 HVDD LINEAR 12 REGULATOR VREF MASTER 5 BIAS & UVLO C3 1.0µF ON/OFF PGND GND Figure ...

Page 7

FUNCTIONAL DESCRIPTION The ML4877 consists of a PWM regulator, a lamp driver/ inverter, a linear regulator and control circuits. This IC, in conjunction with external components, converts a DC battery voltage into the high voltage and high frequency AC signal ...

Page 8

ML4877 FUNCTIONAL DESCRIPTION oscillator frequency versus the value of RT for different values Of CT. This nomograph may be used to select the appropriate value of RT and CT to achieve the desired oscillator frequency for the ML4877. LINEAR REGULATOR ...

Page 9

J1 1 GND DIMMING IRF7416 C20 C24 0.1µF 220µF C22 220µF R18 R15 200 1k C23 1nF C21 1nF R14 Q6 1k 2N3904 R13 Q5 10k 2N3904 1 C19 2 4.7nF 3 4 ...

Page 10

ML4877 Figure 6. 30W CCFL Inverter Board Lamps 10 ...

Page 11

... ORDERING INFORMATION PART NUMBER ML4877CR (END OF LIFE) ML4877ER (OBSOLETE) © Micro Linear 1998 registered trademark of Micro Linear Corporation. All other trademarks are the property of their respective owners. Products described herein may be covered by one or more of the following U.S. patents: 4,897,611; 4,964,026; 5,027,116; 5,281,862; 5,283,483; 5,418,502; ...

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