Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 800-877-6458, 714-898-8121, Fax: 714-893-2570
Page 5
Copyright © 2009
Rev. 1.0, 2009-06-18
WWW.Microsemi .COM
PanelMatch™ LXMG1627-05-4x
5V Dual 4W Programmable CCFL Inverter Module
TM
®
TYPICAL APPLICATION
LXMG1627-05-4x
5V
SET
2
GND
V
HI
V
LO
BRITE
V
IN
SLEEP
SET
1
0V to
2.5V
500k
CCFL
TUBE
NC
NC
ONE OF
TWO
Voltage Source,
DAC, or
Potentiometer
Figure 1 – Brightness Control
(Output current set to maximum)
P.W.
10µs to 500µS
BRITE
LXMG1627-05-4x
0 <
P.W. < 100% of period
PWM Signal
from System
Figure 1A – PWM Brightness Control
LXMG1627-05-4x
SET
2
GND
V
HI
V
LO
SLEEP
SET
1
CCFL
TUBE
BRITE
5V
V
IN
ONE OF
TWO
L L 5.0mA
RMS
L H 5.5mA
RMS
H L 6.0mA
RMS
H H 6.5mA
RMS
L=GND; H=Open
Figure 2 – Maximum Output Current
(SET
1
and SET
2
Inputs)
The brightness control may be a voltage output DAC or
other voltage source, a digital pot or 500k manual pot. The
inverter contains an internal 300k pull-up to typically 4.2V
to bias the pot. A PWM logic level signal (figure 1A) may
be used up to 5V; however the inverter will reach
maximum current at less than 100% duty cycle. This can
be calculated as approximately 2.3V divided by the logic
high voltage level; with 3.3V logic level this corresponds
to about 70% duty cycle for maximum lamp current.
If you need to turn the inverter ON/OFF remotely, connect
to TTL logic signal to the
SLEEP
input.
Connect V
HI
to high voltage wire from the lamp. Connect
V
LO
to the low voltage wire (wire with thinner insulation).
Never connect V
LO
to circuit ground as this will defeat
lamp current regulation. If both lamp wires have heavy
high voltage insulation, connect the longest wire to V
LO
.
This wire is typically white.
Use the SET
1
and SET
2
(see Figure 2) inputs to select the
desired maximum output current. Using these two pins in
combination allows the inverter to match a wide variety of
panels from different manufacturers. Generally the best
lamp lifetime correlates with driving the CCFL at the
manufacturer’s nominal current setting. However the
SET
1
and SET
2
inputs allow the user the flexibility to
adjust the current to the maximum allowable output current
to increase panel brightness at the expense of some
reduced lamp life.
Although the SET pins are designed such that just leaving
them open or grounding them is all that is needed to set the
output current, they can also be actively set. Using a open
collector or open drain logic signal will allow you to
reduce the lamp current for situations where greater dim
range is required, as an example in nighttime situations.
Since the dim ratio is a factor of both the burst duty cycle
and the peak output current, using this technique the
effective dim ratio can be increased greater than the burst
duty cycle alone. Conversely the SET inputs could be used
to overdrive the lamp temporarily to facilitate faster lamp
warm up at initial lamp turn on. Of course any possible
degradation on lamp life from such practices is the users
responsibility since not all lamps are designed to be
overdriven.
The inverter has a built in fault timeout function. If either
or both outputs are open (lamp disconnected or broken) the
inverter will attempt to strike for about a 1.5 seconds and
then shutdown for safety purposes. In order to restart the
inverter it is necessary to toggle the sleep input or cycle the
V
IN
input supply.
A
A
P
P
P
P
L
L
I
I
C
C
A
A
T
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O
O
N
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