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LX1686

Digital Dimming CCFL Controller IC

Microsemi Corporation 

INTEGRATED PRODUCTS

Not Recommended For New Design

LX1686

Digital Dimming CCFL Controller IC

PRODUCTION DATA SHEET

DESCRIPTION

The LX1686 Backlight Controller Safety and reliability features include

IC provides all the control functions a new dual feedback control loop that

needed to implement Microsemi’s

direct drive inverters used to operate

cold cathode fluorescent lamps

(CCFL’s). This IC can be used to

control single or multiple-lamp

configurations. CCFL’s are used for

back or edge lighting of liquid crystal

flat panel displays (LCD’s) and

permits regulation of maximum lamp

strike voltage as well as lamp current.

Regulating maximum lamp voltage

permits the designer to provide for

ample worst case lamp strike voltage

while at the same time conservatively

limit maximum open circuit voltage.

An innovative new strike voltage

typically find application in notebook

computers, web browsers, automotive

and industrial instrumentation, and

entertainment systems.

The LX1686 includes a PWM

controlled lamp current burst circuit

that can provide a > 100:1 dimming

range from a simple zero to 2.5V

potentiometer input. The PWM

dimming burst rate is easily

synchronized to the LCD panel’s frame

rate to prevent interference from

optical beat frequencies.

generation technique enables the nodule

designer to optimize high voltage

transformer design for maximum

operating efficiency with no power

dissipating overhead to guarantee strike

capability

Direct drive topology is a non-

resonant, oscillator-controlled PWM

regulation method. The LX1686 allows

a wide choice of fixed operating

frequencies to match lamp current

frequency to the lamp’s most efficient

operating point, and to minimize high

frequency interference.

IMPORTANT: For the most current data, consult MICROSEMI’s website:

Protected by U.S. Patents 5,615,093; 5,923,129; 5,930,121; 6,198,234; Patents Pending

PRODUCT HIGHLIGHT

5

Standard Analog

4

Dimming Inverter

KEY FEATURES

ƒ RangeMAX™ Wide Range

Dimming (>100:1)

ƒ Synchronizable to Display Video

Frequency

ƒ High Voltage Feedback Loop

Directly Controls Maximum Open

Lamp

ƒ Micro-Amp Sleep Mode

ƒ User Programmable Fixed

Frequency Operation

ƒ Under-Voltage Lockout Feature

With Power-Up Reset

ƒ Built-In Soft-Start Feature

ƒ Operates With 3.3V or 5V power

Supplies

ƒ 100mA Output Drive Capability

APPLICATIONS

ƒ Notebooks

ƒ Instrumentation Display

ƒ Desktop Computer Monitors

ƒ Low Ambient Light Displays

(used in Aircraft, Automobiles,

and Hand-Held Equipment)

BENEFITS

ƒ Extremely High Efficiency From

3.3V to 5V Power Supplies

ƒ Lower Cost Than Conventional

Buck / Royer Inverter Topologies

ƒ Improved Lamp Strike Capability

ƒ Improved Over-Voltage Control

3

Microsemi's

RangeMAX

Light emitted by a CCFL is proportional to the current flowing through it.

2

There are two ways to control the current: by adjusting the amplitude of a

continuous AC current; or, as with RangeMAX technology, by varying the

amount of time a burst of full current is present. RangeMAX technology

1

frees the backlight inverter module designer to operate in a lower

brightness and lower power consumption mode than is possible with

0

conventional amplitude control methods.

0

30

45

60

75

90

105

Light Output (Nits)

Copyright © 2000

Rev. 1.2a, 2005-01-27

PACKAGE ORDER INFO

TA (°C)

Plastic TSSOP

PW 24-PIN

RoHS Complaint / Pb-free Transition D/C: 0442

0 to 85

LX1686CPW

-40 to 85

LX1686IPW

Note: Available in Tape & Reel.

Append the letters “TR” to the part number. (i.e. LX1686CPW-TR)

Microsemi

Integrated Products

11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570

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