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LT1182CS View Datasheet(PDF) - Linear Technology

Part Name
Description
MFG CO.
'LT1182CS' PDF : 24 Pages View PDF
LT1182/LT1183/LT1184/LT1184F
BLOCK DIAGRAM
LT1184/LT1184F CCFL Regulator Top Level Block Diagram
VIN
BAT ROYER
12
14
13
SHUTDOWN 6
0µA TO
100µA
VREF
1.24V
SHUTDOWN
2.4V
REGULATOR
UNDER-
VOLTAGE
LOCKOUT
200kHz
OSC
+
CCFL
V1
0.465V
Q5
1×
Q3
2×
Q4 Q7
5× 9×
THERMAL
SHUTDOWN
LT1184: HIGH-SIDE SENSE RESISTOR
R4 AND GM AMPLIFIER ARE REMOVED.
PIN 13 IS NO CONNECT.
CCFL
VSW
16
R4
0.1
LOGIC 1
–+
D2
gm
6V
R3
1k
Q6
2×
Q11
COMP1
Q8
1×
Q9
Q10
3×
2×
D1
DRIVE 1
Q1
ANTI-
SAT1
+
ILIM
AMP1
GAIN = 4.4
R1
0.125
11
2
REF
ICCFL
5
3
AGND
DIO
LT1184/LT1184F: REFERENCE IS BROUGHT OUT TO PIN 1.
PINS 7, 8, 9, 10 ARE NO CONNECT.
15
BULB
4
CCFL
VC
1
CCFL
PGND
1184 BD02
APPLICATIONS INFORMATION
Introduction
Current generation portable computers and instruments
use backlit Liquid Crystal Displays (LCDs). These displays
also appear in applications extending to medical equip-
ment, automobiles, gas pumps, and retail terminals. Cold
Cathode Fluorescent Lamps (CCFLs) provide the highest
available efficiency in backlighting the display. Providing
the most light out for the least amount of input power is the
most important goal. These lamps require high voltage AC
to operate, mandating an efficient high voltage DC/AC
converter. The lamps operate from DC, but migration
effects damage the lamp and shorten its lifetime. Lamp
drive should contain zero DC component. In addition to
good efficiency, the converter should deliver the lamp
drive in the form of a sine wave. This minimizes EMI and
RF emissions. Such emissions can interfere with other
devices and can also degrade overall operating efficiency.
Sinusoidal CCFL drive maximizes current-to-light conver-
sion in the lamp. The circuit should also permit lamp
intensity control from zero to full brightness with no
hysteresis or “pop-on”.
14
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