LXMG1627-05-44 Datasheet, PDF (5/6 Pages) Microsemi Corporation – 5V Dual 4W CCFL Programmable Inverter Module

PanelMatch™ RangeMAX™ LXMG1627-05-44
®
5V Dual 4W CCFL Programmable Inverter Module
TM
PRODUCTION DATASHEET
TYPICAL APPLICATION
DAC or
Pot
0V to
2.5V _500k
BRITE
5V
V_IN
LAMP_HI
LXMG1627-05-44
CCFL
TUBE
SLEEP
SET₁ SET₂
NC
NC
LAMP_LO
GND
One of
Two
Figure 1 – Brightness Control
(Output current set to maximum)
PWM Signal
from System
BRITE
P.W.
LXMG1627-05-44
2.5µs to 125µS
0 < P.W. < 100% of period
Figure 1A – PWM Brightness Control
5V
BRITE
V_IN
V_HI
LXMG1627-05-44
SLEEP
SET₁ SET₂
GND
CCFL
TUBE
V_LO
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 – Max Output Current
(SET₁ and SET₂ Inputs)
ƒ 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 191k pull-up resistor in series with 43.2k
to 4.2V to bias the pot (see block diagram). 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
ƒ If you need to turn the inverter ON/OFF remotely, connect to
TTL logic signal to the _SLEEP input.
ƒ 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.
ƒ Use the SET₁ and SET₂ (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 SET₁
and SET₂ 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.
ƒ 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 an 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 user’s responsibility since not
all lamps are designed to be overdriven.
ƒ The inverter has a built in fault timeout function. If the output
is open (lamp disconnected or broken) the inverter will
attempt to strike the lamp for about 1.3 seconds, without
success the inverter will shutdown. In order to restart the
inverter it is necessary to toggle the sleep input or cycle the
V_IN input supply. If either high side lamp output is directly
connected to ground the inverter will immediately shutdown.
Copyright © 2008
Rev. 1.0, 2008-12-04
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, 800-877-6458, Fax: [phone]
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