LXMG1618A-03-2X Datasheet, PDF (5/6 Pages) Microsemi Corporation – 3.3V 2.2W CCFL Programmable Inverter Module

PanelMatch™ "A Series" LXMG1618A-03-2x
®
3.3V 2.2W CCFL Programmable Inverter Module
TM
PRODUCTION DATASHEET
TYPICAL APPLICATION
DAC or
Pot
BRITE
3.3V
V_IN
0V to
2.0V _500k
V_HI
LXMG1618A-03-2x
CCFL
TUBE
SLEEP
SET₁ SET₂
NC
NC
V_LO
GND
Figure 1 – Brightness Control
(Output current set to maximum)
PWM Signal
from System
BRITE
P.W.
LXMG1618A-03-2x
10µs to 500µS
0 < P.W. < 100% of period
Figure 1A – PWM Brightness Control
3.3V
BRITE
V_IN
V_HI
LXMG1618A-03-2x
SLEEP
SET₁ SET₂
V_LO
GND
CCFL
TUBE
• The brightness control may be a voltage output DAC or
other voltage source, a digital pot or 500K manual pot.
The inverter contains effectively an internal 338k pull-up
to 3V to bias the pot, if desired; add a resistor to set the
lower threshold voltage above the absolute minimum dim
level capability. 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 2V divided by the logic
high voltage level; with 3.3V logic level this corresponds
to about 60% 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 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.
• 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.
In conjunction with a light sensor or other timer the panel
could be set to higher brightness (maximum output
current) for daytime illumination and lower brightness
(minimum or typical output current) at nighttime. Since
the dim ratio is a factor of the peak output current, using
this technique the effective dim ratio can be increased.
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.
L
L
3.5mA_RMS
L
H
4.0mA_RMS
H
L
4.5mA_RMS
H
H
5.0mA_RMS
L=GND; H= Open
Figure 2 – Max Output Current
(SET₁ and SET₂ Inputs)
• The inverter has a built-in fault timeout function. If the
output is open (lamp disconnected or broken) or shorted
the inverter will attempt to strike the lamp up to about one
second, after which (without success) the inverter will
shutdown. Supply current draw in the shutdown mode is
about 8mA. In order to restart the inverter it is necessary
to toggle the sleep input or cycle the V_IN input supply.
Copyright © 2008
Rev. 1.1, 2009-11-03
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 800-877-6458, 714-898-8121, Fax: [phone]
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