MICROSEMI LXM1641-01

RangeMAX
TM
LXM1641-01/-02/-03
D IGITAL D IMMING Q UAD L AMP CCFL I NVERTER M ODULE
T
H E
I
N F I N I T E
P
O W E R
O F
I
N N O VA T I O N
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R E L I M I N A R Y
DESCRIPTION
RangeMAX Wide Range Dimming, Quad
Output Inverter. The LXM1641 Direct
DriveTM CCFL (Cold Cathode Fluorescent
Lamp) Inverter Modules are specifically designed for driving LCD backlight lamps.
Similar to the LXM1640, the LXM1641 excels in applications where critical parameters
include very wide range dimmability, high efficiency and reliable fail-safe design in a small
form factor. These 12 volt input modules are
specifically designed with desktop and industrial applications in mind.
Unlike the LXM1640 or any traditional
dimming CCFL inverters, the LXM1641 provides the designer a vastly superior display
brightness range. 1000:1+ brightness range
is achievable with a standard LCD display (see
Application Section). Our wide range dimming provides exceptional display readability
at less than 1% of full brightness, allowing
both power savings and low ambient light operating capability (i.e. "night readable").
RangeMAX Digital Dimming Technique. Digital dimming provides flicker-free
brightness control in any wide-range dimming
application. Dimming ratios greater than
1000:1 can be achieved. Incorporation of a
video synchronization feature allows wide
ratio dimming without the display disturbances and interference seen with competitive products.
The modules are equipped with a dimming
input that permits brightness control from an
external potentiometer or DC voltage source.
The resultant "burst drive" that energizes the
S
H E E T
K E Y F E AT U R E S
lamp was designed specifically to ensure that
no premature lamp degradation occurs (see
"How RangeMAX Works" Section).
Failsafe Feature For Multiple Lamp Applications. Our multi-output inverters are
designed to keep your application operating
at near normal brightness in the event that a
lamp fails. This allows the display to remain
"on-line" until lamp replacement is convenient.
Direct Drive Technology. The module
design is based on a new patented1 Direct
Drive topology, which provides a number of
cost and performance advantages. The
LXM1641-xx Direct Drive inverters eliminate
the classic resonant inductor and capacitors,
thus reducing cost and allowing a substantial
reduction in module size.
Universal Connector Configuration.
Linfinity's multiple lamp inverters include a
built in connector array for the most common LCD lamp configurations.
Additional Features. Other benefits of
this new topology are fixed-frequency operation and secondary-side strike-voltage regulation.
Strike-voltage regulation minimizes corona
discharge in the output transformer and related circuitry, providing longer life and higher
reliability. All LXM1641 modules feature
both open and shorted lamp protection.
The LXM1641 is fully customizable (electronically and mechanically) to specific customer requirements.
1
A T A
■
■
■
■
■
■
RangeMAX Wide Range Dimming
8V to 16V Input Voltage Range
Small Form Factor
Easy To Use Brightness Control
MicroAmp SLEEP Mode
Output Short-Circuit Protection And
Automatic Strike-Voltage Regulation
■ Fixed Frequency Operation
■ Universal Connector Configuration
A P P L I C AT I O N S
■ Hi-Brite Displays
■ Desktop Displays
■ Low Ambient Light Conditions (i.e. Aircraft
Cabins, Automobile)
■ Industrial Applications
BENEFITS
■ High Efficiency Reduces Heating Problems
■ Smooth, Flicker Free 0-100% Full-Range
Brightness Control Gives Your Product A
High Quality Image
■ Output Open Circuit Voltage Regulation
Minimizes Corona Discharge For Long Life
And High Reliability
■ Power Efficient, "Low Brightness" Capability
Allows For Advanced Power Management
US Patent Numbers: 5923129 & 5930121
NOTE: For current data & package dimensions, visit our web site: http://www.linfinity.com.
M O D U L E O R D E R I N F O R M AT I O N
Inverter Mates Directly
Part Number
Application
to Panel Connectors
Copyright © 1999
Rev. 0.7 12/99
LXM1641-01
Quad Lamp Panels
JST BHR-03VS-1 (3-pin) &
JST BHR-04VS-1 (4-pin)
LXM1641-02
Sharp 18.1" Panel
JST XHP-9 (9-pin)
LXM1641-03
LG Electronics 18.1" Panel
JST BHSR-02VS-1 (2-pin)
LINFINITY MICROELECTRONICS INC.
11861 WESTERN AVENUE, GARDEN GROVE, CA. 92841, 714-898-8121, FAX: 714-893-2570
1
PRODUCT DATABOOK 1996/1997
RangeMAX
TM
LXM1641-01/-02/-03
D IGITAL D IMMING Q UAD L AMP CCFL I NVERTER M ODULE
P
R E L I M I N A R Y
D
A T A
S
H E E T
A B S O L U T E M A X I M U M R AT I N G S
(Note 1)
Input Supply Voltage (VIN) ....................................................................................................................................................... -0.3V to 16V
Output Voltage, no load .............................................................................................................................. Internally Limited to 1800VRMS
Output Current ............................................................................................................................................ 10.0mARMS (Internally Limited)
Output Power (per Lamp) .................................................................................................................................................................... 6.0W
Input Signal Voltage (BRITE Input) ....................................................................................................................................... -0.3V to 6.5V
Input Signal Voltage (SLEEP, VSYNC Inputs) ................................................................................................................................... -0.3V to VIN
Ambient Operating Temperature .................................................................................................................................................... 0°C to 70°C
Storage Temperature Range ......................................................................................................................................................... -40°C to 85°C
Note 1. Exceeding these ratings could cause damage to the device. All voltages are with respect to Ground.
Currents are positive into, negative out of the specified terminal.
R E C O M M E N D E D O P E R A T I N G C O N D I T I O N S (R.C.)
This module has been designed to operate over a wide range of input and output conditions. However, best efficiency and performance
will be obtained if the module is operated under the condition listed in the 'R.C.' column. Min. and Max. columns indicate values beyond
which the inverter, although operational, will not function optimally.
Parameter
Symbol
Input Supply Voltage Range (Functional)
LXM1641-01, -02
LXM1641-03
LXM1641-01, -02
LXM1641-03
Input Supply Voltage
(Fully Regulated Lamp Current)
Output Power (per Lamp)
Brightness Control Input Voltage Range
Lamp Operating Voltage
Lamp Current (Full Brightness - per Lamp)
Operating Ambient Temperature Range
Recommended Operating Conditions
Min.
R.C.
Max.
8
10
9
10.8
PO
VBRT ADJ
VLAMP
IOLAMP
TA
0.0
300
12
12
12
12
4
Units
16
14
16
13.2
5
2.5
800
675
7.0
0
V
V
V
V
W
V
VRMS
mARMS
°C
70
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, these specifications apply over the recommended operating conditions and 25°C ambient temperature for the LXM1641.
Parameter
Symbol
Test Conditions
LXM1641-xx
Min. Typ.
Max.
Units
Output Pin Characteristics
Full Bright Lamp Current 1641-01,-02
(per Lamp)
1641-03
Minimum Lamp Current (per Lamp)
(Notes 2 & 3)
Lamp Start Voltage
Operating Frequency
IL (MAX)
IL (MIN)
VLS
fO
VBRT ADJ = 2.5VDC, SLEEP = HIGH, Burst Duty = 100%, VIN = 9VDC
VBRT ADJ = 2.5VDC, SLEEP = HIGH, Burst Duty = 100%, VIN = 12VDC
VBRT ADJ = 0VDC, SLEEP = HIGH, Burst Duty = 2%, VIN = 9VDC
VBRT ADJ = -50mVDC, SLEEP = HIGH, Burst Duty = 0.5%, VIN = 9VDC
0°C < TA < 40°C, VIN ≥ 10.8VDC
VBRT ADJ = 2.5VDC, SLEEP = HIGH, VIN = 12VDC
6.3
7.2
1500
52
7.0
8.0
0.14
0.035
57
7.7
8.8
1800
62
mA RMS
mA RMS
mA RMS
mA RMS
VRMS
KHz
BRITE Input
Input Current
Input Voltage for Max. Lamp Current
Input Voltage for Min. Lamp Current
(Note 3)
IBRT
VC
VC
VBRT ADJ = 0VDC
IO (LAMP) = 100% Duty Cycle
IO (LAMP) = 2% Duty Cycle
IO (LAMP) = 0.5% Duty Cycle
-6
-8
2.5
0
-50
-10
2.6
0
µADC
VDC
VDC
mVDC
VIN
0.8
100
VDC
VDC
µADC
SLEEP Input
RUN Mode
SLEEP Mode
Input Current
VSLEEP (HI)
VSLEEP (LO)
ISLEEP
SLEEP = 5.0V
2.2
-0.3
70
75
Note 2. Minimum lamp current required to maintain even light output may vary with display panel.
3. See 1000:1 Dimming Application section for details.
2
Copyright © 1999
Rev. 0.7 12/99
PRODUCT DATABOOK 1996/1997
RangeMAX
TM
LXM1641-01/-02/-03
D IGITAL D IMMING Q UAD L AMP CCFL I NVERTER M ODULE
P
R E L I M I N A R Y
D
A T A
S
H E E T
ELECTRICAL CHARACTERISTICS
Parameter
Symbol
( Continued)
Test Conditions
LXM1641-xx
Min. Typ.
Max.
Units
VSYNC Characteristics
Logic High Level
Logic Low Level
Input Impedance
Pulse Width (Note 4)
Input Frequency
VSYNC (HI)
VSYNC (LO)
ZIN
tPW
fSYNC
4.0
-0.3
60
25
49
66
6.5
1.0
75
250
150
VDC
VDC
kΩ
µs
Hz
5
50
µADC
Power Characteristics
Sleep Current
IIN (MIN)
VIN = 12V DC , SLEEP ≤ 0.8V
Note 4. The module will be functional with pulse widths much larger than 250µs, but will have limited dimming.
Copyright © 1999
Rev. 0.7 12/99
3
PRODUCT DATABOOK 1996/1997
RangeMAX
TM
LXM1641-01/-02/-03
D IGITAL D IMMING Q UAD L AMP CCFL I NVERTER M ODULE
P
R E L I M I N A R Y
D
A T A
S
H E E T
PHYSICAL DIMENSIONS
LXM1641-01
All dimensions are in inches (mm)
6.39 (161)
0.65 (16.5)
CN7
CN1
CN5
0.30 (7.5)
CN6
CN4
5.04 (128)
Top Side
1.03
(26.2)
1.05
(26.6)
1.05
(26.6)
0.96
(24.5)
Ø 0.138 (3.5)
Grounded Mounting Hole - 2 plcs
4.25 (107.925)
CN2
CN3
Bottom Side
0.338 (8.6) Max.
0.13
(3.3)
1.26
(32)
Warning!!
High Voltage Present
At All Output
Connectors
0.060 (1.52) max.
FIGURE 1 — LXM1641-01 Physical Dimensions
Functional Pin Description
Conn.
CN1
Pin
Description
CN1-1, 2
VIN
Input Power Supply. (8V ≤ VIN ≤ 16V)
CN1-3, 4
GND
Power Supply Return.
CN1-5
SLEEP
ON/OFF Control. (2.2V < SLEEP < VIN = ON, -0.3V < SLEEP < 0.8V = OFF)
CN1-6
BRITE
Brightness Control (-0.3V to 2.5VDC). 2.5VDC gives maximum lamp current.
CN1-7, 8
VSYNC
Vertical syncronization input. 49Hz < fSYNC < 150Hz
CN2 thru CN7: Refer to Figure 2
4
Copyright © 1999
Rev. 0.7 12/99
PRODUCT DATABOOK 1996/1997
RangeMAX
TM
LXM1641-01/-02/-03
D IGITAL D IMMING Q UAD L AMP CCFL I NVERTER M ODULE
P
R E L I M I N A R Y
D
A T A
S
H E E T
C O N N E C T O R S C H E M AT I C
CN1
Inverter VHI2
Output 2
8
Inverter VHI1
Output 1
1
2
1
CN2
Inverter
Output 4
VHI3
Inverter
Output 3
2
2
4
3
VHI4
1
N.C.
3
CN4
1
CN6
3
2
2
CN5
1
1
2
N.C.
3
4
CN3
1
CN7
FIGURE 2 — LXM1641-01 Connector Schematic
Note: CN2 and CN3 (shown with dashed lines) are located on the opposite side of the PCB from CN1, CN4,
CN5, CN6, and CN7. Their pin numbers are shown as viewed looking through the printed circuit board.
Connectors:
CN1 = MOLEX 53261-0890
Mates With:
Pins: 50079-8100*, Housing: 51021-0800
CN2, CN3 = JST SM04(4.0)B-BHS-1-TB
JST BHR-04VS-1
CN4, CN7 = JST SM03(4.0)B-BHS-1-TB
JST BHR-03VS-1
CN5, CN6 = JST SM02(8.0)B-BHS-1-TB
JST BHR-03VS-1
* Loose (-8000, Chain) Recommended #26 AWG wiring
Connection Rules
1. Always install FOUR (4) lamps. Operating with fewer lamps may overdrive lamp current at maximum brightness settings.
2. Verify lamp wiring before connecting lamps to the inverter module. Connecting multiple lamps to one of the four inverter output
circuits will result in reduced brightness. The LXM1641-01 module connectors are wired per industry standard. The lamp hot wires
(high voltage wires) are always on pin 1 or 2, and the cold wire (low voltage wire) is always on pin 3 or 4.
Copyright © 1999
Rev. 0.7 12/99
5
PRODUCT DATABOOK 1996/1997
RangeMAX
TM
LXM1641-01/-02/-03
D IGITAL D IMMING Q UAD L AMP CCFL I NVERTER M ODULE
P
R E L I M I N A R Y
D
A T A
S
H E E T
PHYSICAL DIMENSIONS
LXM1641-02
For Direct Connection to Sharp: LQ181E1DG01 (18.1" TFT, 4 lamp)
9.84 (250)
0.94
(24)
7.95 (202)
3.70 (94)
2.44 (62)
1.06
(27)
Ø 0.138 (3.5) Dia. Hole
4 Places (plated)
CN1
1.26
(32)
CN3
0.30
(7.5)
CN2
9.06 (230)
0.20 (5)
0.96
(24.5)
FIGURE 3 — LXM1641-02 Physical Dimensions
All dimensions are in inches (mm)
Connectors:
CN1 = MOLEX 53261-0890
CN2, CN3 = JST S9B-XH-A
Mates With:
Pins: 50079-8100, Housing: 51021-0800
XHP-9
Functional Pin Description
6
Connector
Pin #
Pin Name
CN1-1, 2
CN1-3, 4
CN1-5
CN1-6
CN1-7, 8
CN2-1
CN2-2, 3
CN2-4
CN2-5, 6
CN2-7
CN2-8
CN2-9
CN3-1
CN3-2, 3
CN3-4
CN3-5, 6
CN3-7
CN3-8
CN3-9
VIN
GND
SLEEP
BRITE
VSYNC
VHI1
N.C.
VHI2
N.C.
VLO
N.C.
VLO
VHI3
N.C.
VHI4
N.C.
VLO
N.C.
VLO
Description
Input Power Supply (8V to 16V)
Power Supply Return
ON / OFF Control (2.2V < SLEEP < VIN = ON, -0.3V < SLEEP < 0.8V = OFF
Brightness Control (-0.3V to 2.5V), 2.5V gives max. lamp current
Vertical Sync Input, negative going. 49Hz < fSYNC < 150Hz
High-voltage connection to high side of lamp 1
No Connect
High-voltage connection to high side of lamp 2
No Connect
Connection to low side of lamp 2
No Connect
Connection to low side of lamp 1
High-voltage connection to high side of lamp 4
No Connect
High-voltage connection to high side of lamp 3
No Connect
Connection to low side of lamp 3
No Connect
Connection to low side of lamp 4
Copyright © 1999
Rev. 0.7 12/99
PRODUCT DATABOOK 1996/1997
RangeMAX
TM
LXM1641-01/-02/-03
D IGITAL D IMMING Q UAD L AMP CCFL I NVERTER M ODULE
P
R E L I M I N A R Y
D
A T A
S
H E E T
PHYSICAL DIMENSIONS
LXM1641-03
For Direct Connection to LG LM181E1 18.1" SXGA
9.84 (250)
0.94
(24)
7.95 (202)
3.70 (94)
0.30
(7.5)
2.44 (62)
CN8
CN10
1.06
(27)
1.26
(32)
CN1
CN9
CN11
Ø 0.138 (3.5) Dia. Hole
4 Places (plated)
0.20 (5)
0.96
(24.5)
Note: Connectors CN8, CN9, CN10, and CN11 are mounted
on bottom side of board. Shown looking through board.
FIGURE 4 — LXM1641-03 Physical Dimensions
All dimensions are in inches (mm)
Connectors:
CN1 = MOLEX 53261-0890
CN8, CN9, CN10, CN11 = JST SM02B-BHSS-1-TB
Mates With:
Pins: 50079-8100, Housing: 51021-0800
BHSR-02VS-1
Functional Pin Description
Connector
Pin #
Pin
CN1-1, 2
CN1-3, 4
CN1-5
CN1-6
CN1-7, 8
CN8-1
CN8-2
CN9-1
CN9-2
CN10-1
CN10-2
CN11-1
CN11-2
VIN
GND
SLEEP
BRITE
VSYNC
VHI1
VLO
VHI1
VLO
VHI1
VLO
VHI1
VLO
Copyright © 1999
Rev. 0.7 12/99
Description
Input Power Supply (10V to 14V)
Power Supply Return
ON / OFF Control (2.2V < SLEEP < VIN = ON, -0.3V < SLEEP < 0.8V = OFF)
Brightness Control (-0.3V to 2.5V), 2.5V gives max. lamp current
Vertical Sync Input, negative going. 49Hz < fSYNC < 150Hz
High-voltage connection to high side of lamp 1
Connection to low side of lamp 1
High-voltage connection to high side of lamp 2
Connection to low side of lamp 2
High-voltage connection to high side of lamp 3
Connection to low side of lamp 3
High-voltage connection to high side of lamp 4
Connection to low side of lamp 4
7
PRODUCT DATABOOK 1996/1997
RangeMAX
TM
LXM1641-01/-02/-03
D IGITAL D IMMING Q UAD L AMP CCFL I NVERTER M ODULE
P
R E L I M I N A R Y
D
S
A T A
H E E T
T Y P I C A L C O N N E C T I O N C O N F I G U R AT I O N S
1
These examples illustrate three typical
LCD wiring configurations that are
accomodated by Linfinity's unique
connector array. Linfinity inverters
have multiple lamp connector styles
that are common to the industry,
which are duplicated at both ends of
the module. This permits many
variations of module mounting and
interconnectivity configurations.
1
CCFL Lamps
CN1
LXM1641-01
(1 = Pin 1 Designator)
CN6 CN7
CN4 CN5
1
1
Desktop Display
1
CCFL Lamps
CN1
LXM1641-01*
(1 = Pin 1 Designator)
CN3
CCFL Lamps
CN2
1
Desktop Display
* Connectors CN2 and CN3 are on the bottom side of the inverter.
View shown is looking through the board.
1
1
CCFL Lamps
LXM1641-01
(1 = Pin 1 Designator)
CN6 CN7
CN1
CCFL Lamps
CN4 CN5
1
1
Desktop Display
FIGURE 5 — Connectivity Configuration Examples
8
Copyright © 1999
Rev. 0.7 12/99
PRODUCT DATABOOK 1996/1997
RangeMAX
TM
LXM1641-01/-02/-03
D IGITAL D IMMING Q UAD L AMP CCFL I NVERTER M ODULE
P
R E L I M I N A R Y
D
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H E E T
HOW RANGEMAX WORKS
LAMP VOLTAGE & LAMP CURRENT — Burst Mode Operation
(770VRMS)
(760VRMS)
(7.6mARMS)
(6.7mARMS)
FIGURE 6 — 50% Burst Duty Cycle
FIGURE 7 — 2% Burst Duty Cycle
Rather than using the traditional dimming technique of
varying lamp current magnitude to adjust light output,
RangeMAX inverters use a fixed lamp current value with
a duty cycle control method.
The lamp current burst width can be modulated from
100% (continuous lamp current) down to a 2% duty cycle,
allowing the lamp to be dimmed to less than 1% of its
full brightness.
As can be seen in Trace 4 of Figure 8, careful design
consideration was given to controlling lamp start voltage
to softly start current flow. This eliminates current overshoot that can result in premature cathode wear and reduce lamp life.
FIGURE 8 — 2% Burst Duty Cycle (Expanded Time Base)
High Voltage
Transformer
Transformer
Driver
Ramp
Gen.
VHI1
LAMP 1
Ramp
VSYNC
(6.7mARMS)
Comparator
VBRITE
0-2.5V
DC
(760VRMS)
VSENSE
ISENSE
VLO
FIGURE 9 — RangeMAX Block Diagram
Copyright © 1999
Rev. 0.7 12/99
9
PRODUCT DATABOOK 1996/1997
RangeMAX
TM
LXM1641-01/-02/-03
D IGITAL D IMMING Q UAD L AMP CCFL I NVERTER M ODULE
P
R E L I M I N A R Y
D
A T A
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H E E T
H O W R A N G E M A X W O R K S (continued)
HIGHLIGHTS
■ In applications with no access to a vertical sync, the inverter burst frequency can be allowed to "free run" at 95Hz.
In this non-synchronous mode, minor display disturbances
may be found under certain video conditions. This performance is acceptable for many applications, but synchronization must be used when no disturbance can be tolerated.
■ Separate feedback loops for lamp current and open circuit voltage regulation insure reliable strike under all operating conditions,
automatic over-voltage prevention with broken or failed lamps,
and accurate lamp current regulation.
■ On-board brightness control circuit includes a DC voltage
to pulse width converter that minimizes system design work
and system noise susceptibility. This provides a familiar
and convenient interface while reducing the potential for
externally induced noise which can cause lamp flicker.
■ An on-board oscillator operates the inverter BURST rate
above 95Hz, well beyond standard 50/60Hz video refresh
rates where the eye can perceive pulsing light.
■ RangeMAX inverter modules are designed to operate with
the burst frequency synchronized to the video frame rate.
This provides operation with no visible display disturbances
caused by beat frequencies between the lamps and video
frame rates.
T Y P I C A L 1 0 0 : 1 D I M M I N G A P P L I C AT I O N
9VDC- 16VDC
2.5VDC
5V
0V
Lamp 1
LXM1641-xx
SLEEP
VSYNC
GND
Lamp 4
BRITE
Lamp 3
£ 10k
Lamp 2
VHI4
VHI3
VHI2
VHI1
VIN
VLO
VSYNC
FIGURE 10 — Potentiometer Brightness Control
PWM Signal
from System
P.W.
4.99k
4.7µF
4.99k*
£ 100µs
■ The brightness control may be a simple 10k
potentiometer or a voltage output DAC. A PWM
signal from a micro-controller may also be used
with a suitable filter such as shown in Figure 11.
■ If synchronization to the video framerate is
desired, connect the vertical sync pulse from the
system video controller to the appropriate VSYNC input.
If no video synchronization is desired, connect VSYNC
to ground.
■ If you need to turn the inverter ON/OFF remotely,
connect a 3V or 5V logic signal to the SLEEP input.
If remote ON/OFF is not needed, connect the
SLEEP input to VIN or any other voltage greater than
2.2VDC.
■ Connect VHI to high voltage wire from the lamp.
Connect VLO to the low voltage wire (wire with
thinner insulation). If both lamp wires have
heavy high voltage insulation, connect the
longest wire to VLO. VLO is connected directly to
ground (GND pin) on the inverter PCB. Always
insure a good lamp return by using a wire. Do
not rely on a chassis ground connection.
BRITE
LXM1641-xx
0 £ P.W. £ 100% of period
* use 4.99k for 5V PWM amplitude, 15k for 3.3V PWM
amplitude, and omit for 2.5V PWM amplitude.
FIGURE 11 — PWM Brightness Control
10
Copyright © 1999
Rev. 0.7 12/99
PRODUCT DATABOOK 1996/1997
RangeMAX
TM
LXM1641-01/-02/-03
D IGITAL D IMMING Q UAD L AMP CCFL I NVERTER M ODULE
P
R E L I M I N A R Y
D
A T A
S
H E E T
1 0 0 0 : 1 D I M M I N G A P P L I C AT I O N
The following application defines techniques capable of delivering dimming ranges in the 250:1 and 1000:1 range. As is widely
understood, these techniques will provide general capabilities and actual
system performance will vary with panel design, CCFTs, ambient temperature and a number of other variables outside the control of the
inverter. These methods can be used in conjunction with other techniques such as lamp heating and matching.
Wide ratio (1000:1) dimming can be accomplished using the Linfinity
inverter in two ways:
IOLAMP (mA)
7
.14
.070
1) By varying the input voltage on the brightness pin as
indicated in Figure 12. Caution must be exercised when
applying negative voltage to the brightness control input.
Applying more than -300mV to any inverter input will cause
inverter malfunction (see Absolute Maximum Ratings).
2) By making a resistor value change on the module. If this
option is preferrable, please contact the factory for application assistance.
Both methods discussed will provide a lower duty cycle
operation than is necessary in a 100:1 dimming application.
Careful consideration should be made with regards to display quality
0.7
-100mV
0V
2.5V
VBRT ADJ (V)
FIGURE 12 — Average Lamp Current vs. VBRITE Voltage
(per Lamp)
at these dimming levels. At very low brightness levels, even very small
amounts of noise on the VBRITE line can cause flicker on the display, so
special care must be given to grounding, filtering and shielding the
inverter from the digital logic and clock.
FA I L S A F E F E AT U R E F O R M U L T I P L E L A M P O P E R AT I O N S
Our multi-output inverters are designed to keep your application
operating at near normal brightness in the event that a lamp fails.
This allows the display to remain "on-line" until lamp replacement
is convenient.
Linfinity "parallels" the lamps so that if any lamps break, most
of the current is added to the remaining good lamps. CCFLs will
respond with more brightness for a period of time. Operating time
in this mode will be a function of the lamps age but should be
typically in the order of hundreds of hours.
This operating characteristic can provide adequate display
performance for a limited, but useful period of time. Shortening
of the lamp life in this mode is typically not a concern as it is
recommended that all lamps in a display be replaced at the same
time.
Lamps
IS
RangeMAX INVERTERS
Also available in Single
Output LXM1611-01,
LXM1612-xx-xx and Dual
Output LXM1621-xx versions
for multiple lamp applications.
FIGURE 13 — Quad Output Stage
RangeMAX and Direct Drive are trademarks of Linfinity Microelectronics Inc.
PRELIMINARY DATA - Information contained in this document is pre-production data, and is proprietary to LinFinity. It may
not modified in any way without the express written consent of LinFinity. Product referred to herein is offered in sample form
only, and Linfinity reserves the right to change or discontinue this proposed product at any time.
Copyright © 1999
Rev. 0.7 12/99
11