Datasheet

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LT1182/LT1183/LT1184/LT1184F

CCFL/LCD Contrast

Switching Regulators

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Wide Input Voltage Range: 3V to 30V

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Low Quiescent Current

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High Switching Frequency: 200kHz

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CCFL Switch: 1.25A, LCD Switch: 625mA

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Grounded or Floating Lamp Configurations

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Open-Lamp Protection

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Positive or Negative Contrast Capability

FEATURES

DESCRIPTION

APPLICATIONS

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

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Notebook and Palmtop Computers

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Portable Instruments

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Automotive Displays

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Retail Terminals

90% Efficient Floating CCFL Configuration with Dual Polarity LCD Contrast

TYPICAL APPLICATION

, LTC and LT are registered trademarks of Linear Technology Corporation.

C12

2.2µF

35V

BAT

8V TO 28V

POSCON

NEGCON

1182/3 TA01

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.

1

2

3

4

5

6

7

16

15

14

13

12

11

10

CCFL



DIO

CCFL V



AGND

SHDN

LCD V

CCFL V



BULB

BAT

ROYER



FBP

FBN

LCD V

CCFL

PGND

LCD

PGND

LT1182

LAMP

UP TO 6mA

R1

750Ω

L2

100µH

321 5

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.



C7, 1µF

C1*

0.068µF

D1

1N5818

D2

1N914

D4

1N914

V (PWM)

0V TO 5V

1kHz PWM

SHUTDOWN

C8, 0.68µF

R7, 10K

C5

1000pF

R2

220k

R3

100k

C3A

2.2µF

35V

C11

22µF

35V

R13

8.45k

R14

1.21k

R10, 10k, 1%R9, 4.99k, 1%

C4

2.2µF

IN

≥ 3V

D3

1N5934A

24V

C3B

2.2µF

35V

C2

27pF

3kV

C1 MUST BE A LOW LOSS CAPACITOR, C1 = WIMA MKP-20

Q1, Q2 = ZETEX ZTX849 OR ROHM 2SC5001

L1 = COILTRONICS CTX210605

L2 = COILTRONICS CTX100-4

L3 = COILTRONICS CTX02-12403

*DO NOT SUBSTITUTE COMPONENTS

COILTRONICS (407) 241-7876



Q2* Q1*

N = 1:2



0µA TO 45µA ICCFL

CURRENT GIVES

0mA TO 6mA 

BULB CURRENT.

THIS IS EQUAL TO

0% TO 90% DUTY

CYCLE FOR THE

PWM SIGNAL.

R12

20k

R5, 43.2k, 1%

C6

2.2µF

R4 

46.4k

D5

BAT85

C10

0.01µF

R11, 20k, 1%

C9, 0.01µF

2



4



CCFL BACKLIGHT APPLICATION CIRCUITS CONTAINED IN THIS

DATA SHEET ARE COVERED BY U.S. PATENT NUMBER 5408162 

AND OTHER PATENTS PENDING

Summary of content (24 pages)

PAGE 1
LT1182/LT1183/LT1184/LT1184F CCFL/LCD Contrast Switching Regulators U DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ ■ The LT®1182/LT1183 are dual current mode switching regulators that provide the control function for Cold Cathode 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.
PAGE 2
LT1182/LT1183/LT1184/LT1184F U DESCRIPTION LT1184/LT1184F pin out the reference for simplified programming of lamp current. The LT1182/LT1183/LT1184/LT1184F operate with input supply voltages from 3V to 30V. The ICs also have a battery supply voltage pin that operates from 4.5V to 30V. The LT1182/LT1183 draw 9mA typical quiescent current while the LT1184/LT1184F draw 6mA typical quiescent current. An active low shutdown pin typically reduces total supply current to 35µA for standby operation.
PAGE 3
LT1182/LT1183/LT1184/LT1184F ELECTRICAL CHARACTERISTICS TA = 25°C, VIN = 5V, BAT = Royer = Bulb = 12V, ICCFL = SHUTDOWN = CCFL VSW = Open, DIO = GND, CCFL VC = 0.5V, (LT1182/LT1183) LCD VC = 0.5V, LCD VSW = Open, (LT1182) FBN = FBP = GND, (LT1183) FB = GND, (LT1183/LT1184/LT1184F) REF = Open, unless otherwise specified.
PAGE 4
LT1182/LT1183/LT1184/LT1184F ELECTRICAL CHARACTERISTICS TA = 25°C, VIN = 5V, BAT = Royer = Bulb = 12V, ICCFL = SHUTDOWN = CCFL VSW = Open, DIO = GND, CCFL VC = 0.5V, (LT1182/LT1183) LCD VC = 0.5V, LCD VSW = Open, (LT1182) FBN = FBP = GND, (LT1183) FB = GND, (LT1183/LT1184/LT1184F) REF = Open, unless otherwise specified. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VREF – ICCFL Summing Voltage Measured on LT1183 ● 0.760 0.725 0.795 0.795 0.830 0.865 V V ● 0.740 0.705 0.775 0.775 0.810 0.
PAGE 5
LT1182/LT1183/LT1184/LT1184F U W TYPICAL PERFORMANCE CHARACTERISTICS LT1184/LT1184F Supply Current vs Temperature 10 13 9 90 12 8 8O 10 9 8 VIN = 30V VIN = 3V 7 SHUTDOWN CURRENT (µA) 11 100 7 6 VIN = 30V 5 VIN = 3V 4 3 6 2 5 1 4 –75 – 50 – 25 0 25 50 75 100 125 150 175 TEMPERATURE (°C) 0 –75 – 50 –25 0 25 50 75 100 125 150 175 TEMPERATURE (°C) VIN = 3V 1 0 –75 –50 –25 0 25 50 75 100 125 150 175 TEMPERATURE (°C) CCFL Frequency vs Temperature 240 230 1.1 1.0 0.9 0.8 0.
PAGE 6
LT1182/LT1183/LT1184/LT1184F U W TYPICAL PERFORMANCE CHARACTERISTICS ICCFL Summing Voltage Load Regulation 10 5 4 3 2 1 0 –1 –2 –3 –4 –5 –6 –7 –8 –9 –10 T = –55°C T = 25°C T = 125°C 0 20 40 60 80 100 120 140 160 180 200 ICCFL PROGRAMMING CURRENT (µA) LT1182 • G10 1.0 ICCFL = 50µA ICCFL = 10µA 4.90 1.6 1.4 I(DIO) = 10mA I(DIO) = 5mA 0.8 0.6 I(DIO) = 1mA 0.4 I(DIO) = 5mA 98 97 96 95 –75 – 50 –25 0 25 50 75 100 125 150 175 TEMPERATURE (°C) LT1182 • G16 6 0.6 0.
PAGE 7
LT1182/LT1183/LT1184/LT1184F U W TYPICAL PERFORMANCE CHARACTERISTICS LCD VC Low Clamp Voltage vs Temperature 2.4 1.2 1.1 1.0 0.9 0.8 0.7 LDC VC HIGH CLAMP VOLTAGE (V) 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.10 0 –75 –50 –25 0 25 50 75 TEMPERATURE (°C) 0.6 –75 – 50 –25 0 25 50 75 100 125 150 175 TEMPERATURE (°C) 2.2 2.1 2.0 1.9 1.8 1.
PAGE 8
LT1182/LT1183/LT1184/LT1184F U W TYPICAL PERFORMANCE CHARACTERISTICS FBP Reference Voltage Line Regulation vs Temperature 1.254 1.244 1.234 1.224 1.214 –75 – 50 –25 0 25 50 75 100 125 150 175 TEMPERATURE (°C) 0.03 1.0 0.9 0.025 FBP INPUT BIAS CURRENT (µA) 1.264 0.020 0.015 0.010 0.005 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.
PAGE 9
LT1182/LT1183/LT1184/LT1184F U W TYPICAL PERFORMANCE CHARACTERISTICS LCD VSW Sat Voltage vs Switch Current CCFL VSW Sat Voltage vs Switch Current CCFL VSW Current Limit vs Duty Cycle 2.0 1.0 2.5 T = 25°C 0.7 T = 125°C 0.6 T = –5°C 0.5 0.4 0.3 0.2 CCFL VSW CURRENT LIMIT (A) 0.8 LCD VSW SAT VOLTAGE (V) CCFL VSW SAT VOLTAGE (V) 0.9 1.6 1.2 T = 25°C T = 125°C T = –5°C 0.8 0.4 2.0 T = 0°C T = 25°C 1.5 T = 125°C MINIMUM 1.0 0.5 0.1 0 0.3 0 0.9 1.2 0.6 SWITCH CURRENT (A) 0 1.
PAGE 10
LT1182/LT1183/LT1184/LT1184F U U U PIN FUNCTIONS LT1182/LT1183/LT1184/LT1184F CCFL PGND (Pin 1): This pin is the emitter of an internal NPN power switch. CCFL switch current flows through this pin and permits internal, switch-current sensing. The regulators provide a separate analog ground and power ground(s) to isolate high current ground paths from low current signal paths. Linear Technology recommends the use of star-ground layout techniques.
PAGE 11
LT1182/LT1183/LT1184/LT1184F U U U PIN FUNCTIONS Bulb (Pin 15): This pin connects to the low side of a 7V threshold comparator between the BAT and Bulb pins. This circuit sets the maximum voltage level across the primary side of the Royer converter under all operating conditions and limits the maximum secondary output under start-up conditions or open lamp conditions. This eases transformer voltage rating requirements.
PAGE 12
LT1182/LT1183/LT1184/LT1184F U U U PIN FUNCTIONS LCD VSW (Pin 9): This pin is the collector of the internal NPN power switch for the LCD contrast regulator. The power switch provides a minimum of 625mA. Maximum switch current is a function of duty cycle as internal slope compensation ensures stability with duty cycles greater than 50%.
PAGE 13
LT1182/LT1183/LT1184/LT1184F W BLOCK DIAGRAM LT1182/LT1183 CCFL/LCD Contrast Regulator Top Level Block Diagram VIN BAT 14 12 SHUTDOWN 6 SHUTDOWN UNDERVOLTAGE LOCKOUT 2.4V REGULATOR ROYER 13 THERMAL SHUTDOWN LCD VSW CCFL VSW 9 16 200kHz OSC Q2 DRIVE 2 LOGIC 2 ANTISAT2 ILIM AMP2 Q5 1× GAIN = 4.4 0µA TO 100µA + V2 1.24V – Q6 2× R1 0.125Ω – Q11 Q3 2× Q4 5× CCFL + – – + + 7 + ILIM AMP1 GAIN = 4.
PAGE 14
LT1182/LT1183/LT1184/LT1184F W BLOCK DIAGRAM LT1184/LT1184F CCFL Regulator Top Level Block Diagram VIN BAT 14 12 SHUTDOWN 6 SHUTDOWN UNDERVOLTAGE LOCKOUT 2.4V REGULATOR ROYER 13 LT1184: HIGH-SIDE SENSE RESISTOR R4 AND GM AMPLIFIER ARE REMOVED. PIN 13 IS NO CONNECT. THERMAL SHUTDOWN CCFL VSW 16 200kHz OSC LOGIC 1 R4 0.1Ω ANTISAT1 + – gm D2 6V COMP1 + R3 1k Q5 1× Q6 2× Q1 DRIVE 1 ILIM AMP1 R1 0.125Ω – Q11 GAIN = 4.4 Q3 2× + 0µA TO 100µA Q4 5× CCFL – VREF 1.
PAGE 15
LT1182/LT1183/LT1184/LT1184F U W U U APPLICATIONS INFORMATION Manufacturers offer a wide array of monochrome and color displays. LCD display types include passive matrix and active matrix. These displays differ in operating voltage polarity (positive and negative contrast voltage displays), operating voltage range, contrast adjust range, and power consumption.
PAGE 16
LT1182/LT1183/LT1184/LT1184F U W U U APPLICATIONS INFORMATION change in quiescent current. An active low shutdown pin typically reduces total supply current to 35µA by shutting off the 2.4V regulator and locking out switching action for standby operation. The ICs incorporate undervoltage lockout by sensing regulator dropout and locking out switching below about 2.5V. The regulators also provide thermal shutdown protection that locks out switching in the presence of excessive junction temperatures.
PAGE 17
LT1182/LT1183/LT1184/LT1184F U W U U APPLICATIONS INFORMATION cycles. Lamp current is controlled by monitoring one-half of the average lamp current. The diode conducting on negative half cycles has one-tenth of its current diverted to the CCFL pin and nulls against the source current provided by the lamp current programmer circuit. The compensation capacitor on the CCFL VC pin provides stable loop compensation and an averaging function to the rectified sinusoidal lamp current.
PAGE 18
LT1182/LT1183/LT1184/LT1184F U W U U APPLICATIONS INFORMATION very large if the total impedance in this path is small and the voltage source has high current capability. Linear Technology recommends the use of an aluminum electrolytic for the transformer center tap bypass capacitor with an ESR greater than or equal to 0.5Ω. This lowers the peak surge currents to an acceptable level. In general, the wire and trace inductance in this path also help reduce the di/ dt of the surge current.
PAGE 19
LT1182/LT1183/LT1184/LT1184F U W U U APPLICATIONS INFORMATION Size Constraints Applications Support Tighter length, width, and height constraints for CCFL and LCD contrast control circuitry are the result of LCD display enclosure sizes remaining fairly constant while display screen sizes have increased. Space requirements for connector hardware include the input power supply and control signal connector, the lamp connector, and the contrast output voltage connector.
PAGE 20
LT1182/LT1183/LT1184/LT1184F U TYPICAL APPLICATIONS N 90% Efficient Grounded CCFL Configuration with Negative Polarity LCD Contrast UP TO 6mA LAMP C1 MUST BE A LOW LOSS CAPACITOR, C1 = WIMA MKP-20 Q1, Q2 = ZETEX ZTX849 OR ROHM 2SC5001 10 L1 = COILTRONICS CTX210605 C2 27pF 3kV 6 L1 L2 = COILTRONICS CTX100-4 3 L3 = COILTRONICS CTX02-12403 2 + *DO NOT SUBSTITUTE COMPONENTS C5 1000pF COILTRONICS (407) 241-7876 THE ICCFL CURRENT REQUIRED FOR AN RMS BULB CURRENT IS: ICCFL (9 × 10–3) (IBULB).
PAGE 21
LT1182/LT1183/LT1184/LT1184F U TYPICAL APPLICATIONS N LT1184F Floating CCFL with Potentiometer Control of Lamp Current UP TO 6mA LAMP ALUMINUM ELECTROLYTIC IS RECOMMENDED FOR C3B WITH AN ESR ≥ 0.5Ω TO PREVENT DAMAGE TO THE LT1184F HIGH-SIDE SENSE RESISTOR DUE TO SURGE CURRENTS AT TURN-ON.
PAGE 22
LT1182/LT1183/LT1184/LT1184F U TYPICAL APPLICATIONS N LT1182/LT1183 ICCFL PWM Programming V (PWM) 0V TO 5V 1kHz PWM 0% to 90% DC = 0µA to 50µA LT1183 ICCFL PWM Programming with VREF R2 40.5k R1 40.5k FROM VREF TO ICCFL PIN + C1 2.2µF R1 AND R2 ARE IDEAL VALUES. USE NEAREST 1% VALUE. V (PWM) 0V TO 5V 1kHz PWM 0% to 90% DC = 0µA to 50µA R1 330Ω Q1 VN2222L R2 7.15k 1182 TA04 + LT1184/LT1184F ICCFL PWM Programming V (PWM) 0V TO 5V 1kHz PWM 0% to 90% DC = 0µA to 50µA R3 7.
PAGE 23
LT1182/LT1183/LT1184/LT1184F U TYPICAL APPLICATIONS N LT1182 LCD Contrast Positive Boost Converter + 1 2 3 4 5 C8 0.068µF 6 R7 33K 7 8 CCFL PGND CCFL VSW ICCFL BULB DIO BAT LT1182 CCFL VC ROYER AGND VIN SHDN FBP LCD VC FBN LCD PGND LCD VSW BAT 8V TO 28V C13 2.2µF 35V L3 50µH COILTRONICS CTX50-4 16 D5 1N914 15 + 14 13 + 12 C4 2.2µF POSCON VOUT ≥ VIN C11 22µF 35V R12 20k VIN ≥ 3V R13 8.45k 1% 11 R14 1.21k 1% C10 0.
PAGE 24
LT1182/LT1183/LT1184/LT1184F U TYPICAL APPLICATIONS N LT1182 LCD Contrast Positive to Negative/Charge Pump Converter 3 4 5 6 C8 0.068µF R7 33K 7 CCFL VSW ICCFL BULB DIO BAT 16 + 15 14 LT1182 13 CCFL VC ROYER AGND VIN SHDN FBP LCD VC FBN 8 LCD PGND LCD VSW C13 2.2µF 35V + 12 C4 2.2µF 11 BAT 8V TO 28V L3 CTX50-4 COILTRONICS CTX50-4 C11 22µF 35V VIN ≥ 3V D5 1N914 + 2 CCFL PGND C9 0.01µF D4 1N914 + 1 10 NEGCON |VOUT| ≥ VIN C11 22µF 35V 9 R9 4.