LT1182/LT1183/LT1184/LT1184F
CCFL/LCD Contrast
Switching Regulators
U
FEATURES
DESCRIPTION
The LT®1182/LT1183 are dual current mode switching
regulators that provide the control function for Cold Cath-
odeFluorescentLighting(CCFL)andLiquidCrystalDisplay
(LCD) Contrast. The LT1184/LT1184F provide only the
CCFLfunction.TheICsincludehighcurrent,highefficiency
switches, an oscillator, a reference, output drive logic,
control blocks and protection circuitry. The LT1182 per-
mits positive or negative voltage LCD contrast operation.
The LT1183 permits unipolar contrast operation and pins
out an internal reference. The LT1182/LT1183 support
grounded and floating lamp configurations. The LT1184F
supports grounded and floating lamp configurations. The
LT1184 supports only grounded lamp configurations. The
, LTC and LT are registered trademarks of Linear Technology Corporation.
■
Wide Input Voltage Range: 3V to 30V
■
Low Quiescent Current
■
High Switching Frequency: 200kHz
■
CCFL Switch: 1.25A, LCD Switch: 625mA
■
Grounded or Floating Lamp Configurations
■
Open-Lamp Protection
■
Positive or Negative Contrast Capability
U
APPLICATIONS
■
Notebook and Palmtop Computers
■
Portable Instruments
■
Automotive Displays
Retail Terminals
■
U
TYPICAL APPLICATION
90% Efficient Floating CCFL Configuration with Dual Polarity LCD Contrast
UP TO 6mA
LAMP
ALUMINUM ELECTROLYTIC IS RECOMMENDED FOR C3B WITH AN
ESR ≥ 0.5Ω TO PREVENT DAMAGE TO THE LT1182 HIGH-SIDE
SENSE RESISTOR DUE TO SURGE CURRENTS AT TURN-ON.
CCFL BACKLIGHT APPLICATION CIRCUITS CONTAINED IN THIS
DATA SHEET ARE COVERED BY U.S. PATENT NUMBER 5408162
AND OTHER PATENTS PENDING
C2
27pF
3kV
10
6
C1 MUST BE A LOW LOSS CAPACITOR, C1 = WIMA MKP-20
Q1, Q2 = ZETEX ZTX849 OR ROHM 2SC5001
L1 = COILTRONICS CTX210605
L1
3
2
1
5
4
BAT
8V TO 28V
L2 = COILTRONICS CTX100-4
+
C3B
+
+
C3A
2.2µF
35V
2.2µF
L3 = COILTRONICS CTX02-12403
*DO NOT SUBSTITUTE COMPONENTS
COILTRONICS (407) 241-7876
C5
EITHER NEGCON OR POSCON
MUST BE GROUNDED.
GROUNDING NEGCON GIVES
VARIABLE POSITIVE CONTRAST
FROM 10V TO 30V.
GROUNDING POSCON GIVES
VARIABLE NEGATIVE CONTRAST
FROM –10V TO –30V.
R2
35V
1000pF
220k
R1
C1*
0.068µF
750Ω
0µA TO 45µA ICCFL
CURRENT GIVES
0mA TO 6mA
BULB CURRENT.
THIS IS EQUAL TO
0% TO 90% DUTY
C12
2.2µF
35V
R3
100k
Q2*
Q1*
POSCON
D5
D3
L3
BAT85
CYCLE FOR THE
PWM SIGNAL.
1N5934A
24V
6
9
C11 +
22µF
L2
100µH
4
D1
1N5818
35V
D2
1N914
R4
1
2
3
4
5
6
7
8
16
2
CCFL
PGND
CCFL V
46.4k
SW
R5, 43.2k, 1%
V (PWM)
0V TO 5V
1kHz PWM
1%
NEGCON
15
14
13
12
11
10
9
I
BULB
BAT
N = 1:2
CCFL
D4
1N914
+
C6
2.2µF
DIO
C7, 1µF
R12
20k
LT1182
C
V
IN
≥ 3V
CCFL V
AGND
SHDN
ROYER
+
C4
2.2µF
R13
8.45k
1%
V
IN
SHUTDOWN
FBP
FBN
C8, 0.68µF
C9, 0.01µF
R14
1.21k
1%
C10
0.01µF
LCD V
LCD
C
R7, 10K
LCD V
SW
PGND
R11, 20k, 1%
R9, 4.99k, 1%
R10, 10k, 1%
5V
1182/3 TA01
1