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LXMG1621-04

P1-P3P4-P6P7-P9P10-P10
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 7
Copyright © 2007
Rev. 1.2, 2010-08-20
WWW.Microsemi .COM
RangeMAX
™
LXMG1621-xx
DIGITAL DIMMING DUAL LAMP CCFL INVERTER MODULE
P
RODUCTION
D
ATA
S
HEET
TM
®
HOW THE RANGEMAX WORKS
LAMP VOLTAGE & LAMP CURRENT – BURST MODE OPERATION
Figure 3 – 50% Burst Duty Cycle
Figure 4 – 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 3 of Figure 5 photo at right, 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 5 – 2% Burst Duty Cycle (Expanded Time Base)
Ramp Gen.
Transformer
Driver
High Voltage
Transformer
Comparator
Ramp
+
-
I
SENSE
V
SENSE
V
BRITE
0.25 -
2.2V
DC
V
SYNC
LAMP
V
LO
V
HI
LAMP
V
LO
V
HI
Figure 6 – RangeMAX Simplified Block Diagram
HIGHLIGHTS
• Integrated 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
about 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.
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Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 8
Copyright © 2007
Rev. 1.2, 2010-08-20
WWW.Microsemi .COM
RangeMAX
™
LXMG1621-xx
DIGITAL DIMMING DUAL LAMP CCFL INVERTER MODULE
P
RODUCTION
D
ATA
S
HEET
TM
®
HOW THE RANGEMAX WORKS (CONTINUED)
HIGHLIGHTS (CONTINUED)
• 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.
TYPICAL APPLICATION
LXMG1621-xx
12V
V
SYNC
V
SYNC
GND
V
HI1
V
LO
BRITE
Figure 7- Brightness Control
V
IN
SLEEP
5V
0
< 10k
2.5V
DC
V
HI2
P.W.
< 100µs
BRITE
LXMG1621-
xx
0 < P.W. < 100% of period
PWM Signal
from System
Figure 8 - PWM Brightness Control
4.7µF
4.99k*
4.99k
* use 4.99k for 5V PWM amplitude, 15k for 3.3V PWM
amplitude, and omit for 2.5V PWM amplitute.
• 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 8.
• If synchronization to the video frame rate is desired,
connect the vertical sync pulse from the system video
controller to the appropriate V
SYNC
input. If no video
synchronization is desired, connect V
SYNC
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 V
IN
or
any other voltage greater than 2.2V
DC
.
• Connect V
HI
to high voltage wire from the lamp. Connect
V
LO
to the low voltage wire (wire with thinner insulation).
If both lamp wires have heavy high voltage insulation,
connect the longest wire to V
LO
. V
LO
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
.
RangeMAX INVERTERS
Also available in single lamp inverters are the
LXMG1612-12-xx or LXMG1615-xx-xx, as well as the
12V dual lamp LXMG1623-xx-xx, LXMG1622-12-xx,
and the Quad output LXMG1643-12-6x versions for
multiple lamp applications.
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Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 9
Copyright © 2007
Rev. 1.2, 2010-08-20
WWW.Microsemi .COM
RangeMAX
™
LXMG1621-xx
DIGITAL DIMMING DUAL LAMP CCFL INVERTER MODULE
P
RODUCTION
D
ATA
S
HEET
TM
®
WIDER DIMMING APPLICATION
The following application defines techniques capable of
delivering dimming ranges in the 250:1 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 (250:1) dimming can be accomplished using the
Microsemi inverter in two ways:
1. By varying the input voltage on the brightness pin as
indicated in Figure 9. Caution must be exercised when
applying negative voltage to the brightness control input.
Applying more then –300mV to any inverter input will cause
inverter malfunction (see Absolute Maximum Ratings).
-100mV 0V 2.5V
.070
.14
0.7
7
V
BRT_ADJ
(V)
I
OLAMP
(mA)
Figure 9 – Average Lamp Current vs. V
BRITE
Voltage (per Lamp)
CN2
C30
U9
T1
R58
C32
C33
R59
C35
R22
R48
R62
R63
R60
R31
R57
R55R52
R54
R53
R56
R51
Q11
R50
C39
R49
R89
C37
R61
Q10
Backside of Module
U7
Figure 10 – Locating The Resistor on the LXMG1621-xx
2. By making a resistor value change on the module.
Remove R61 for maximum dimming range or increase R61
value to desired minimum dim range setting (see figure 10).
Care should be exercised since at a low enough dim setting the
inverter will be unable to detect that the lamp has started and
will initiate lamp strike (kickoff) voltage. This will result in
lamp flicker. For repeatable low light levels the BRITE input
DC supply must be a very clean stable voltage source, at low
dim inputs.
If you plan to completely remove R61 it is recommended tha
t
you ensure that a minimum voltage above zero remain on the
BRITE input to prevent the above flicker problem. This
minimum voltage may need to be adjusted for each individual
inverter module. If you are using a pot to control the BRITE
input then a separate trim pot on the low side would accomplish
the same goal.
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 regard to display
quality 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 signals.
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P1-P3P4-P6P7-P9P10-P10

LXMG1621-04

Mfr. #:
Buy LXMG1621-04
Manufacturer:
Microchip / Microsemi
Description:
EL/CCFL Inverters & Accessories CCFL Inverter Module - Dual Lamp
Lifecycle:
New from this manufacturer.
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