Not Recommended For New Design
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
Copyright © 2000
Rev. 1.2a, 2005-01-27
WWW.Microsemi .COM
LX1686
Di
ital Dimmin
CCFL Controller IC
INTEGRATED PRODUCTS
DESCRIPTION
The LX1686 Backlight Controller
IC provides all the control functions
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
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.
Safety and reliability features include
a new dual feedback control loop that
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
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
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Light Output (Nits)
Power Used (Watts)
Standard Analog
Dimming Inverter
Microsemi's
RangeMAX
KEY FEATURES
RangeMAX™ Wide Range
Dimming (>100:1)
Synchronizable to Display Video
Frequency
High Voltage Feedback Loop
Directly Controls Maximum Open
Lamp
Micro-Amp Sleep Mode
User Programmable Fixed
Frequency Operation
Under-Voltage Lockout Feature
With Power-Up Reset
Built-In Soft-Start Feature
Operates With 3.3V or 5V power
Supplies
100mA Output Drive Capability
APPLICATIONS
Notebooks
Instrumentation Display
Desktop Computer Monitors
Low Ambient Light Displays
(used in Aircraft, Automobiles,
and Hand-Held Equipment)
BENEFITS
Extremely High Efficiency From
3.3V to 5V Power Supplies
Lower Cost Than Conventional
Buck / Royer Inverter Topologies
Improved Lamp Strike Capability
Improved Over-Voltage Control
PACKAGE ORDER INFO
PW
Plastic TSSOP
24-PIN
T
A
(°C)
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)
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L
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Light emitted by a CCFL is proportional to the current flowing through it.
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
frees the backlight inverter module designer to operate in a lower
brightness and lower power consumption mode than is possible with
conventional amplitude control methods.
