ML4876CR MICRO-LINEAR [Micro Linear Corporation], ML4876CR Datasheet

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ML4876CR

Manufacturer Part Number
ML4876CR
Description
LCD Backlight Lamp Driver with Contrast
Manufacturer
MICRO-LINEAR [Micro Linear Corporation]
Datasheet

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Quantity
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ML4876CR
Manufacturer:
PHI
Quantity:
40
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ML4876CR
Manufacturer:
FAIRCHILD/仙童
Quantity:
20 000
GENERAL DESCRIPTION
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.
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.
BLOCK DIAGRAM
15
12
20
6
5
4
2
3
ON/OFF
0.1V
HVDD
VREF
LON
F GATE
F ILIM
FEA–
FEA+
+
+
REGULATOR
MASTER
LINEAR
UVLO
BIAS
13
&
VDD
Q
Q R
LCD Backlight Lamp Driver with Contrast
VDD
S
1
FEA OUT
17
+
GND
Q
Q R
S
+
SHOT
ONE
16V
DR3
18
B ON
R Q
S
Q
CLK
DR1
FEATURES
19
* THIS PART IS END OF LIFE AS OF JULY 1, 2000
B OFF
Backlight lamp driver with differential drive
Up to 30% lower power for same light output
Low standby current (< 10µA)
Improved efficiency ( 95%)
Allows all N-channel MOSFET drive
Low switching losses
Resonant threshold detection
Buck regulator uses synchronous rectification
THRESHOLD
OSCILLATOR
RESONANT
DETECTOR
9
DELAY
EDGE
C
NEG
DR1
11
T
B SYNC OUT
+
T
Q
Q
8
LEA OUT
DR2
DR2
ML4876*
+
+
L GATE 1
L GATE 2
0.2V
L RTD
0.5V
LEA–
10
14
16
7
JULY 2000
1

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ML4876CR Summary of contents

Page 1

LCD Backlight Lamp Driver with Contrast GENERAL DESCRIPTION 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 ...

Page 2

ML4876 PIN CONFIGURATION PIN DESCRIPTION PIN NAME DESCRIPTION 1 FEA OUT Output of flyback (contrast) error amplifier 2 FEA– Negative input of flyback (contrast) error amplifier 3 FEA+ Positive input of flyback (contrast) error amplifier Logic input. ...

Page 3

ABSOLUTE MAXIMUM RATINGS Absolute maximum ratings are those values beyond which the device could be permanently damaged. Absolute maximum ratings are stress ratings only and functional device operation is not implied. Supply Current (I ) ............................................... 75mA CC Output Current, ...

Page 4

ML4876 ELECTRICAL CHARACTERISTICS SYMBOL PARAMETER FLYBACK REGULATOR (Continued) Current Limit Comparator Threshold Input Bias Current Propagation Delay Output Drivers Output High - F Gate Output Low - F Gate Rise & Fall Time HIGH VOLTAGE INVERTER Oscillator Nominal Frequency Discharge ...

Page 5

ELECTRICAL CHARACTERISTICS SYMBOL PARAMETER SUPPLY VDD Supply Current (No Load) VDD Supply Current VDD Supply Current VREF Output Voltage VREF Load Regulation VREF Line Regulation VREF Line, Load, Temp Note 1: Limits are guaranteed by 100% testing, sampling, or correlation ...

Page 6

ML4876 INPUT 5V to 18V CONTRAST D1 25V VOLTAGE –20V MAX. (ADJUSTABLE 25V R12 R2 1. 100k C11 0 200k CONTRAST ADJUST 6 C3 U2-A 1.0 ...

Page 7

FUNCTIONAL DESCRIPTION The ML4876 consists of a PWM regulator, a lamp driver/ inverter, a linear regulator, a flyback regulator, and control circuits. This IC, in conjunction with external components, converts a DC battery voltage into the high voltage and high ...

Page 8

ML4876 FUNCTIONAL DESCRIPTION CONTRAST CONTROL GENERATOR The contrast voltage generator is a separate regulator in a flyback configuration. In conjunction with the external transformer (T3), MOSFET (Q1), diode (D1), and assorted capacitors and resistors, it provides an adjustable DC output ...

Page 9

... ORDERING INFORMATION PART NUMBER ML4876CR (END OF LIFE) ML4876ER (OBSOLETE) © Micro Linear 1998 registered trademark of Micro Linear Corporation. All other trademarks are the property of their respective owners. Products described herein may be covered by one or more of the following U.S. patents: 4,897,611; 4,964,026; 5,027,116; 5,281,862; 5,283,483; 5,418,502; ...

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