LT1183_15 Datasheet, PDF (1/24 Pages) Linear Technology – CCFL/LCD Contrast Switching Regulators

LT1182/LT1183/LT1184/LT1184F
CCFL/LCD Contrast
Switching Regulators
FEATURES
s _{Wide Input Voltage Range: 3V to 30V}
s _{Low Quiescent Current}
s _{High Switching Frequency: 200kHz}
s _{CCFL Switch : 1.25A, LCD Switch: 625mA}
s _{Grounded or Floating Lamp Configurations}
s _{Open-Lamp Protection}
s _{Positive or Negative Contrast Capability}
U
APPLICATIONS
s _{Notebook and Palmtop Computers}
s _{Portable Instruments}
s _{Automotive Displays}
s _{Retail Terminals}
DESCRIPTION
The LT^®1182/LT1183 are dual current mode switching
regulators that provide the control function for Cold Cath-
ode Fluorescent Lighting (CCFL) and Liquid Crystal Display
(LCD) Contrast. The LT1184/LT1184F provide only the
CCFL function. The ICs include high current, high efficiency
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.
TYPICAL APPLICATION
90% Efficient Floating CCFL Configuration with Dual Polarity LCD Contrast
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.
C1 MUST BE A LOW LOSS CAPACITOR, C1 = WIMA MKP-20
Q1, Q2 = ZETEX ZTX849 OR ROHM 2SC5001
UP TO 6mA
LAMP
C2
27pF
10 6
3kV
CCFL BACKLIGHT APPLICATION CIRCUITS CONTAINED IN THIS
DATA SHEET ARE COVERED BY U.S. PATENT NUMBER 5408162
AND OTHER PATENTS PENDING
L1
L1 = COILTRONICS CTX210605
L2 = COILTRONICS CTX100-4
L3 = COILTRONICS CTX02-12403
*DO NOT SUBSTITUTE COMPONENTS
C5
R2
1000pF _220k
3
2 1 45
+ C3B
2.2µF
35V
COILTRONICS [phone]
0µA TO 45µA ICCFL
CURRENT GIVES
0mA TO 6mA
BULB CURRENT.
THIS IS EQUAL TO
0% TO 90% DUTY
CYCLE FOR THE
PWM SIGNAL.
D5
BAT85
R4
46.4k
V (PWM) 1%
0V TO 5V
1kHz PWM _{C6 +}
2.2µF
R5, 43.2k, 1%
C7, 1µF
C1*
0.068µF
R3
100k
Q2*
Q1*
1 _CCFL
PGND
2
I_CCFL
16
CCFL V_SW
15
BULB
3
DIO
14
BAT
4
LT1182
13
CCFL V_C
ROYER
L2
100µH
D1
1N5818
5
AGND
12
V_IN
SHUTDOWN
6
C8, 0.68µF
7
R7, 10K ₈
SHDN
LCD V_C
LCD
PGND
11
FBP
10
FBN
9
LCD V_SW
R9, 4.99k, 1%
+ _C3A
2.2µF
35V
R1
750Ω
+ C12
2.2µF
35V
BAT
8V TO 28V
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.
D3
L3
1N5934A
24V ⁴
6 C11 +
22µF
D2 ₂
1N914
9 ^35V
+
C9, 0.01µF
V_IN
≥ 3V
C4
2.2µF
N = 1:2 _D4
1N914
R12
20k
R13
8.45k
1%
C10
0.01µF
R14
1.21k
1%
POSCON
NEGCON
R10, 10k, 1% R11, 20k, 1%
5V
1182/3 TA01
1