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RangeMAX
TM
Wide Range Dimming (>100:1)
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Synchronizable To Display Video Frequency
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High Voltage Feedback Loop Directly
Controls Maximum Open Lamp And
Minimum Strike Voltages
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Transformer Protected From Over-Heating
During Lamp Striking
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Micro-Amp Sleep Mode
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User-Programmable Fixed Frequency
Operation
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Under-Voltage Lockout Feature With Power-
Up Reset
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Built-In Soft-Start Feature
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Operates With 3.3V or 5V Power Supplies
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100mA Output Drive Capability
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Notebooks
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Instrumentation Displays
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Desktop Computer Monitors
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Low Ambient Light Displays (used in
Aircraft, Automobiles, and Hand-held
Equipment)
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Extemely High Efficiency From 3.3V or 5V
Power Supplies
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Lower Cost Than Conventional Buck / Royer
Inverter Topologies
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Improved Lamp Strike Capability
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Improved Over-Voltage Control
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.
T
H E
I
N F I N I T E
P
O W E R
O F
I
N N O V A T I O N
LX1686
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.
1
11861 W
ESTERN
A
VENUE
, G
ARDEN
G
ROVE
, CA. 92841, 714-898-8121, F
AX
: 714-893-2570
L
I N
F
I N I T Y
M
I C R O E L E C T R O N I C S
I
N C
.
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.
Light Output (Nits)
P
2
0
30
45
60
75
90
105
5
4
3
1
Standard Analog
Dimming Inverter
LinFinity's
RangeMAX
Note: All surface-mount packages are available in Tape & Reel.
Append the letter "T" to part number. (i.e. LX1686CPWT)
PW
Plastic TSSOP
24-pin
NOTE:
For current data & package dimensions, visit our web site:
http://www.linfinity.com.