|LXM1621-02||DIGITAL DIMMING DUAL LAMP CCFL INVERTER MODULE|
|LXM1621-02 Datasheet PDF : 11 Pages |
DIGITAL DIMMING DUAL LAMP CCFL INVERTER MODULE
PRELIMINARY DATA SHEET
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
Wide ratio (250:1) dimming can be accomplished using the
Linfinity inverter in two ways:
1. By varying the input voltage on the brightness pin as
indicated in Figure 9. Caution must be exercised when Figure 9 – Average Lamp Current vs. VBRITE Voltage (per Lamp)
applying negative voltage to the brightness control input.
Applying more then –300mV to any inverter input will cause
inverter malfunction (see Absolute Maximum Ratings).
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
Backside of Module
lamp flicker. For repeatable low light levels the BRITE input
DC supply must be a very clean stable voltage source, at low
If you plan to completely remove R61 it is recommended that
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
Figure 10 – Locating The Resistor on the LXM1621-xx
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.
Rev. 0.8, 2003-08-28
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
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