ML4876 Datasheet, PDF (1/9 Pages) Micro Linear Corporation – LCD Backlight Lamp Driver with Contrast

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JULY 2000
ML4876*
LCD Backlight Lamp Driver with Contrast
GENERAL DESCRIPTION
FEATURES
The ML4876 is an ideal solution for driving small cold
cathode fluorescent tubes (CCFL) used in liquid crystal
display (LCD) backlight applications. It provides the
dimming ballast control and the contrast control for the
LCD display.
By utilizing differential drive the ML4876 can deliver the
same light output with significantly less input power
compared to existing single ended drive schemes.
Improvements as high as 30% can be realized when using
low power lamps and advanced LCD screen housings. This
increased light output is achieved because the differential
drive configuration is much less sensitive, and therefore
less power is wasted in the capacitive parasitics that exist
in the backlight housing. An additional benefit of this
configuration is an even distribution of light.
s Backlight lamp driver with differential drive
s Up to 30% lower power for same light output
s Low standby current (< 10µA)
s Improved efficiency (»95%)
s Allows all N-channel MOSFET drive
s Low switching losses
s Resonant threshold detection
s Buck regulator uses synchronous rectification
The ML4876 is optimized for portable applications where
high efficiency is critical to maximize battery life. The
high efficiency is achieved by a resonant scheme with
zero voltage switching.
* THIS PART IS END OF LIFE AS OF JULY 1, 2000
BLOCK DIAGRAM
13
VDD
HVDD
VDD
15
LINEAR
6
REGULATOR
ON/OFF
VREF
5
MASTER
BIAS
&
UVLO
LON
4
QS
QR
17
GND
18
B ON
DR3
ONE
SHOT
+
– 16V
SQ
RQ
19
B OFF
DR1
11
B SYNC OUT
DR1
NEG
EDGE
DELAY
Q
T
Q
F GATE
12
F ILIM
20
+
0.1V ^–
FEA–
2
–
FEA+
3
+
QS
QR
–
+
RESONANT
THRESHOLD
DETECTOR
–
+
CLK
OSCILLATOR
L RTD
10
L GATE 1
DR2
14
L GATE 2
DR2
16
0.5V
–
+
–
7
LEA–
+
0.2V
FEA OUT
1
CT
9
LEA OUT
8
1