RangeMAX
T
H E
TM
LX1686
D
A T A
D
I G I TA L
D
I M M I N G
C C F L C
O N T R O L L E R
I C
I
N F I N I T E
P
O W E R
O F
I
N N O VA T I O N
P
R E L I M I N A R Y
S
H E E T
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.
K E Y F E AT U R E S
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
s
s
s
Notebooks
Instrumentation Displays
Desktop Computer Monitors
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
NOTE:
For current data & package dimensions, visit our web site:
http://www.linfinity.com.
PRODUCT HIGHLIGHT
R
ANGE
MAX
5
VS
.
A
NALOG
D
IMMING
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.
Power Used (Watts)
Standard Analog
Dimming Inverter
4
3
2
1
LinFinity's
RangeMAX
0
30
45
60
75
90
105
Light Output (Nits)
PA C K A G E O R D E R I N F O
T
A
(°C)
0 to 85
PW
Plastic TSSOP
24-pin
LX1686CPW
Note: All surface-mount packages are available in Tape & Reel.
Append the letter "T" to part number. (i.e. LX1686CPWT)
Copyright © 2000
Rev. 0.4 1/00
L
IN
F
INITY
M
ICROELECTRONICS
I
NC
.
11861 W
ESTERN
A
VENUE
, G
ARDEN
G
ROVE
, CA. 92841, 714-898-8121, F
AX
: 714-893-2570
1
MICROSEMI [ MICROSEMI CORPORATION ]
