LX1686 Datasheet, PDF (1/5 Pages) Microsemi Corporation – Digital Dimming CCFL Controller IC

T H E I N F I N I T E P O W E R O F I N N O VAT I O N
RangeMAX^TM
LX1686
DIGITAL DIMMING CCFL CONTROLLER IC
PRELIMINARY DATA SHEET
DESCRIPTION
The LX1686 Backlight Controller IC
provides all the control functions needed
to implement Linfinity’s direct drive in-
verters used to operate cold cathode fluo-
rescent 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 appli-
cation in notebook computers, web
browsers, automotive and industrial in-
strumentation, and entertainment sys-
tems.
The LX1686 includes a PWM con-
trolled lamp current burst circuit that
can provide a >100:1 dimming range from
a simple zero to 2.5V potentiometer in-
put. 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 in-
clude a new dual feedback contol loop
that permits regulation of maximum lamp
strike voltage as well as lamp current.
Regulating maximum lamp voltage per-
mits the designer to provide for ample
worst case lamp strike voltage while at
the same time conservatively limit maxi-
mum open circuit voltage.
An innovative new strike voltage
generation technique enables the mod-
ule designer to optimize high voltage
transformer design for maximum oper-
ating efficiency with no power dissipat-
ing overhead to guarantee strike capa-
bility.
Direct drive topology is a non-reso-
nant, oscillator-controlled PWM regu-
lation method. The LX1686 allows a
wide choice of fixed operating frequen-
cies to match lamp current frequency to
the lamp’s most efficient operating point,
and to minimize high frequency interfer-
ence.
NOTE: For current data & package dimensions, visit our web site: http://www.linfinity.com.
KEY FEATURES
s RangeMAX^TM Wide Range Dimming (>100:1)
s Synchronizable To Display Video Frequency
s High Voltage Feedback Loop Directly
Controls Maximum Open Lamp And
Minimum Strike Voltages
s Transformer Protected From Over-Heating
During Lamp Striking
s Micro-Amp Sleep Mode
s User-Programmable Fixed Frequency
Operation
s Under-Voltage Lockout Feature With Power-
Up Reset
s Built-In Soft-Start Feature
s Operates With 3.3V or 5V Power Supplies
s 100mA Output Drive Capability
A P P L I C AT I O N S
s Notebooks
s Instrumentation Displays
s Desktop Computer Monitors
s Low Ambient Light Displays (used in
Aircraft, Automobiles, and Hand-held
Equipment)
BENEFITS
s Extemely High Efficiency From 3.3V or 5V
Power Supplies
s Lower Cost Than Conventional Buck / Royer
Inverter Topologies
s Improved Lamp Strike Capability
s Improved Over-Voltage Control
PRODUCT HIGHLIGHT
RANGEMAX VS. ANALOG DIMMING
Light emitted by a CCFL is proportional to the current
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Standard Analog
Dimming Inverter
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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.
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RangeMAX technology frees the backlight inverter
LinFinity's
RangeMAX
module designer to operate in a lower brightness and
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lower power consumption mode than is possible with
conventional amplitude control methods.
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0
30
45
60
75
90
105
Light Output (Nits)
PACKAGE ORDER INFO
T_A (°C)
PW
Plastic
24-pin
TSSOP
0 to 85
LX1686CPW
Note: All surface-mount packages are available in Tape & Reel.
Append the letter "T" to part number. (i.e. LX1686CPWT)
LINFINITY MICROELECTRONICS INC.
Copyright © 2000
Rev. 0.4 1/00
11861 WESTERN AVENUE, GARDEN GROVE, CA. 92841, 714-898-8121, FAX: [phone]
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