LXM1621-02 View Datasheet(PDF) - Microsemi Corporation
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LXM1621-02 Datasheet PDF : 11 Pages
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INTEGRATED PRODUCTS
RangeMAX
LXM1621-xx
DIGITAL DIMMING DUAL LAMP CCFL INVERTER MODULE
PRELIMINARY DATA SHEET
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.
VBRITE
0.25 -
2.2VDC
Comparator
Ramp +
-
Ramp Gen.
Transformer
Driver
High Voltage
Transformer
VSYNC
VSENSE
ISENSE
Figure 6 – RangeMAX Simplified Block Diagram
Figure 5 – 2% Burst Duty Cycle (Expanded Time Base)
VHI
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
VLO
reducing the potential for externally induced noise, which
can cause lamp flicker.
• An on-board oscillator operates the inverter BURST rate
VHI
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
VLO
disturbances caused by beat frequencies between the
lamps and video frame rates.
Copyright 2000
Rev. 0.8, 2003-08-28
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 7
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