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LT1186F DAC Programmable CCFL Switching Regulator (Bits-to-NitsTM)
FEATURES
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APPLICATIONS
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face modes including standard SPI mode and pulse mode. On power-up, the DAC counter resets to half-scale and the Wide Battery Input Range: 4.5V to 30V DAC configures to SPI or pulse mode depending on the CS Grounded Lamp or Floating Lamp Configurations signal level. In SPI mode, the system microprocessor Open Lamp Protection serially transfers the present 8-bit data and reads back the Precision 50A Full-Scale DAC Programming Current previous 8-bit data. In pulse mode, the upper six bits of the Standard SPI Mode or Pulse Mode DAC configure as increment-only (1-wire interface) or DAC Setting Is Retained in Shutdown increment/decrement (2-wire interface) operation depending on the DIN signal level.
Notebook and Palmtop Computers Portable Instruments Retail Terminals
DESCRIPTION
The LT (R)1186F is a fixed frequency, current mode, switching regulator that provides the control function for Cold Cathode Fluorescent Lighting (CCFL). The IC includes an efficient high current switch, an oscillator, output drive logic, control circuitry and a micropower 8-bit 50A fullscale current output DAC. The DAC provides simple "bitsto-lamp current control" and communicates in two inter-
TYPICAL APPLICATION
90% Efficient Floating CCFL with 1-Wire (Increment Only) Pulse Mode Control of Lamp Current
D1 BAT85 CCFL BACKLIGHT APPLICATION CIRCUITS CONTAINED IN THIS DATA SHEET ARE COVERED BY U.S. PATENT NUMBER 5408162 AND OTHER PATENTS PENDING 1 2 3 C7, 1F CCFL PGND ICCFL DIO CCFL VSW BULB 16 15 R2 220k C5 1000pF 3 2 1 C3B 2.2F 35V R1 750 4 5 UP TO 6mA LAMP 10 6 C2 27pF 3kV L1 L1 = COILTRONICS CTX210605 L2 = COILTRONICS CTX100-4 *DO NOT SUBSTITUTE COMPONENTS COILTRONICS (407) 241-7876 BAT 8V TO 28V
14 BAT LT1186F 4 13 CCFL VC ROYER 5 AGND SHDN CLK CS VCC IOUT DOUT 12 11 10
SHUTDOWN FROM MPU
6 7 8
DIN 9
ALUMINUM ELECTROLYTIC IS RECOMMENDED FOR C3A AND C3B. MAKE 3CB ESR 0.5 TO PREVENT DAMAGE TO THE LT1186F HIGH-SIDE SENSE RESISTOR DUE TO SURGE CURRENTS AT TURN-ON 0A TO 50A ICCFL CURRENT GIVES C1 MUST BE A LOW LOSS CAPACITOR, C1 = WIMA MKP-20 0mA TO 6mA LAMP CURRENT Q1, Q2 = ZETEX ZTX849 OR ROHM 2SC5001 FOR A TYPICAL DISPLAY.
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The LT1186F control circuitry operates from a logic supply voltage of 3.3V or 5V. The IC also has a battery supply voltage pin that operates from 4.5V to 30V. The LT1186F draws 6mA typical quiescent current. An active low shutdown pin reduces total supply current to 35A for standby operation and the DAC retains its last setting. A 200kHz switching frequency minimizes magnetic component size. Current mode switching techniques with cycle-by-cycle limiting gives high reliability and simple loop frequency compensation. The LT1186F is available in a 16-pin narrow SO package.
, LTC and LT are registered trademarks of Linear Technology Corporation. Bits-to-Nits is a trademark of Linear Technology Corporation. 1 Nit = 1 Candela/meter2
+
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C3A 2.2F 35V
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VIN 3.3V OR 5V C4 2.2F
C1* 0.068F R3 100k
Q2*
Q1*
L2 100H
D1 1N5818
LT1186F * TA01
FOR ADDITIONAL CCFL/LCD CONTRAST APPLICATION CIRCUITS, REFER TO THE LT1182/83/84/84F DATA SHEET
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LT1186F
ABSOLUTE MAXIMUM RATINGS
VCC ........................................................................... 7V BAT, Royer, BULB .................................................. 30V CCFL VSW ............................................................... 60V Shutdown ................................................................. 6V ICCFL Input Current .............................................. 10mA DIO Input Current (Peak, < 100ms).................... 100mA Digital Inputs ................................ - 0.3V to VCC + 0.3V Digital Outputs .............................. - 0.3V to VCC + 0.3V DAC Output Voltage ....................... - 20V to VCC + 0.3V Junction Temperature (Note 1) ........................... 100C Operating Ambient Temperature Range LT1186FC ............................................ 0C to 100C LT1186FI .......................................... - 40C to 100C Storage Temperature Range ................ - 65C to 150C Lead Temperature (Soldering, 10 sec)................ 300C
PACKAGE/ORDER INFORMATION
TOP VIEW CCFL PGND 1 ICCFL 2 DIO 3 CCFL VC 4 AGND 5 SHDN 6 CLK 7 CS 8 16 CCFL VSW 15 BULB 14 BAT 13 ROYER 12 VCC 11 IOUT 10 DOUT 9 DIN
ORDER PART NUMBER LT1186FCS LT1186FIS
S PACKAGE 16-LEAD PLASTIC SO TJMAX = 100C, JA = 100C/W
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
TA = 25C, VCC = SHUTDOWN = DIN = CS = 3.3V, BAT = Royer = BULB = 12V, ICCFL = CCFL VSW = Open, DOUT = Three-State, DIO = IOUT = CLK = GND, CCFL VC = 0.5V, unless otherwise specified.
xSYMBOL PARAMETER IQ ISHDN Supply Current SHUTDOWN Supply Current SHUTDOWN Input Bias Current SHUTDOWN Threshold Voltage f DC(MAX) BV Switching Frequency Maximum Switch Duty Cycle Switch Breakdown Voltage Switch Leakage Current ICCFL Summing Voltage ICCFL Summing Voltage for Input Programming Current CCFL VC Offset Sink Current CCFL VC Source Current for ICCFL Programming Current CCFL VC to DIO Current Servo Ratio CCFL VC Low Clamp Voltage CCFL VC High Clamp Voltage CCFL VC Switching Threshold Measured at CCFL VSW, ISW = 50mA, ICCFL = 100A, CCFL VC = Open Measured at CCFL VSW
q
CONDITIONS 3V VCC 6.5V, 1/2 Full-Scale DAC Output Current SHUTDOWN = 0V, CCFL VC Open (Note 2) SHUTDOWN = 0V, CCFL VC = Open
q q q
MIN
TYP 6 35 5
MAX 9.5 70 10 1.2 225 240
UNITS mA A A V kHz kHz % % V
0.45 175 160 80 75 60
0.85 200 200 85 85 70
Measured at CCFL VSW VSW = 12V, Measured at CCFL VSW VSW = 30V, Measured at CCFL VSW 3V VCC 6.5V
q
20 40 0.425 0.385 0.465 0.465 5 -5
q q q q q q
0.505 0.555 15 15 5.20 5.20 104 0.3 2.4 1.3
ICCFL = 0A to 100A CCFL VC = 1.5V, Positive Current Measured into Pin ICCFL = 25A, 50A, 75A, 100A, CCFL VC = 1.5V TJ < 0C DIO = 5mA out of Pin, Measure I(VC) at CCFL VC = 1.5V VBAT - VBULB = BULB Protect Servo Voltage ICCFL = 100A CCFL VSW DC = 0%
5 4.95 4.95 99 0.1 2.1 0.95
4.70 4.60 94 1.7 0.6
A/A A/A A/mA V V V
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A A V V mV A
LT1186F
ELECTRICAL CHARACTERISTICS
TA = 25C, VCC = SHUTDOWN = DIN = CS = 3.3V, BAT = Royer = BULB = 12V, ICCFL = CCFL VSW = Open, DOUT = Three-State, DIO = IOUT = CLK = GND, CCFL VC = 0.5V, unless otherwise specified.
SYMBOL PARAMETER CCFL High-Side Sense Servo Current CCFL High-Side Sense Servo Current Line Regulation BULB Protect Servo Voltage BULB Input Bias Current ILIM VSAT IQ ISW CCFL Switch Current Limit CCFL Switch On Resistance Supply Current Increase During CCFL Switch On Time DAC Resolution DAC Full-Scale Current DAC Zero Scale Current DAC Differential Nonlinearity DAC Supply Voltage Rejection Logic Input Current VIH VIL VOH VOL IOZ fCLK tCKS tCSS tDV tDS tDH tDO tCKHI tCKLO tCSH tDZ tCKH High Level Input Voltage Low Level Input Voltage High Level Output Voltage Low Level Output Voltage Three-State Output Leakage Clock Frequency Setup Time, CLK Before CS Setup Time, CS Before CLK CS to DOUT Valid Data in Setup Time Before CLK Data in Hold Time After CLK CLK to DOUT Valid CLK High Time CLK Low Time CLK Before CS CS to DOUT In Hi-Z CS Before CLK See Test Circuits See Test Circuits See Test Circuits 3V VCC 6.5V, IOUT = Full Scale, V(IOUT) = 0.465V 0V VIN VCC VCC = 3.3V VCC = 5V VCC = 3.3V VCC = 5V VCC = 3.3V, IO = 400A VCC = 5V, IO = 400A VCC = 3.3V, IO = 1mA VCC = 5V, IO = 2mA VCS = VCC V(IOUT) = 0.465V, Measured in SPI Mode
q
CONDITIONS ICCFL = 100A, I(VC) = 0A at CCFL VC = 1.5V TJ < 0C BAT = 5V to 30V, ICCFL = 100A, I(VC) = 0A at CCFL VC = 1.5V
q q q q
MIN 0.93 0.91
TYP 1.00 1.00 0.1
MAX 1.07 1.07 0.16 150 7.5 9 3.0 2.6 1.0 30
UNIT A A %/V A V A A A mA/A Bits
CCFL High-Side Sense Supply Current Current Measured into BAT and Royer Pins ICCFL = 100A, I(VC) = 0A at CCFL VC = 1.5V, Servo Voltage Measured between BAT and BULB Pins ICCFL = 100A, I(VC) = 0A at CCFL VC = 1.5V Duty Cycle = 50% Duty Cycle = 75% (Note 3) CCFL ISW = 1A CCFL ISW = 1A
50 6.5
100 7.0 5
q q q
1.25 0.9
1.9 1.6 0.6 20 8
48.5 47.0
50 50
51.5 53.0 200 2.0
A A nA LSB LSB A V V
V(IOUT) = 0.465V, Measured in SPI Mode
q q q q q q q q q q q q
2 1.9 2
4 1
0.45 0.80 2.1 2.4 0.4 0.4 5 2 150 400 150 150 150 150 200 250 150 400 400
V V V V V V A MHz ns ns ns ns ns ns ns ns ns ns ns
SERIAL INTERFACE (Notes 4, 5)
q q q q q q q q q q q q
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LT1186F
ELECTRICAL CHARACTERISTICS
TA = 25C, VCC = SHUTDOWN = DIN = CS = 3.3V, BAT = Royer = BULB = 12V, ICCFL = CCFL VSW = Open, DOUT = Three-State, DIO = IOUT = CLK = GND, CCFL VC = 0.5V, unless otherwise specified.
SYMBOL tCSLO tCSHI PARAMETER CS Low Time CS High Time CONDITIONS fCLK = 2MHz
q q
MIN 4550 400
TYP
MAX
UNIT ns ns
SERIAL INTERFACE (Notes 4, 5)
The q denotes specifications which apply over the specified operating temperature range. Note 1: TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formula: LT1186FCS: TJ = TA + (PD)(100C/W) Note 2: Does not include switch leakage.
Note 3: For duty cycles (DC) between 50% and 80%, minimum guaranteed switch current is given by ILIM = 1.4(1.393 - DC) for the LT1186F due to internal slope compensation circuitry. Note 4: Timings for all input signals are measured at 0.8V for a High-toLow transition and 2.0V for a Low-to-High transition. Note 5: Timings are guaranteed but not tested.
TYPICAL PERFORMANCE CHARACTERISTICS
Supply Current vs Temperature
10 9 SHUTDOWN CURRENT (A) 8
90 8O 70 60 50 40 30 20 10 0 -75 -50 -25 0 25 50 75 100 125 150 175 TEMPERATURE (C)
LT1186F * G02
SHUTDOWN INPUT BIAS CURRENT (A)
SUPPLY CURRENT (mA)
7 6 5 4 3 2 1 0 -75 - 50 -25 0 25 50 75 100 125 150 175 TEMPERATURE (C)
LT1186F * G01
Shutdown Threshold Voltage vs Temperature
1.2 240
SHUTDOWN THRESHOLD VOLTAGE (V)
1.1 CCFL FREQUENCY (kHz) 1.0 0.9 0.8 0.7 0.6 -75 -50 -25 0 25 50 75 100 125 150 175 TEMPERATURE (C)
LT1186F * G04
CCFL MAXIMUM DUTY CYCLE (%)
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Shutdown Current vs Temperature
100
6 5 4 3 2 1
Shutdown Input Bias Current vs Temperature
VCC = 5V VCC = 3V
VCC = 5V VCC = 3V
0 -75 -50 -25 0 25 50 75 100 125 150 175 TEMPERATURE (C)
LT1186F * G03
Frequency vs Temperature
95 93 91 89 87 85 83 81 79 77
0 25 50 75 100 125 150 175 TEMPERATURE (C)
LT1186F * G05
Maximum Duty Cycle vs Temperature
230 220 210 200 190 180 170 160 -75 -50 -25
75 -75 - 50 -25 0 25 50 75 100 125 150 175 TEMPERATURE (C)
LT1186F * G06
LT1186F TYPICAL PERFORMANCE CHARACTERISTICS
ICCFL Summing Voltage vs Temperature
0.53 0.52 0.51 0.50 0.49 0.48 0.47 0.46 0.45 0.44 0.43 0.42 0.41 0.40 0.39 0.38 -75 - 50 -25 0 25 50 75 100 125 150 175 TEMPERATURE (C)
LT1186F * G07
CCFL VC SINK OFFSET CURRENT (A)
ICCFL SUMMING VOLTAGE (mV)
ICCFL SUMMING VOLTAGE (V)
CCFL VC Source Current for ICCFL Programming Current vs Temperature
5.10
CCFL VC SOURCE CURRENT FOR ICCFL PROGRAMMING CURRENT (A/A)
I(DIO) = 10mA 0.8 0.6 0.4 0.2 0 -75 -50 -25 0 25 50 75 100 125 150 175 TEMPERATURE (C)
LT1186F * G11
NEGATIVE DIO VOLTAGE (V)
5.05
POSITIVE DIO VOLTAGE (V)
5.00 4.95 4.90 4.85
ICCFL = 100A ICCFL = 50A ICCFL = 10A
4.80 -75 -50 -25 0 25 50 75 100 125 150 175 TEMPERATURE (C)
LT1186F * G10
VC to DIO Current Servo Ratio vs Temperature
CCFL VC DIO CURRENT SERVO RATIO (A/mA)
103
CCFL VC LOW CLAMP VOLTAGE (V)
CCFL VC HIGH CLAMP VOLTAGE (V)
102 101 100 99 98 97 96 95 -75 - 50 -25 0 25 50 75 100 125 150 175 TEMPERATURE (C)
LT1186F * G13
I(DIO) = 10mA I(DIO) = 1mA I(DIO) = 5mA
UW
ICCFL Summing Voltage Load Regulation
5 4 3 2 1 0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 0
VC Sink Offset Current vs Temperature
10 9 8 7 6 5 4 3 2 1 CCFL VC = 0.5V 0 -1 -2 -3 -75 - 50 -25 0 25 50 75 100 125 150 175 TEMPERATURE (C)
LT1186F * G09
CCFL VC = 1.5V
T = -55C
CCFL VC = 1.0V
T = 25C
T = 125C
20 40 60 80 100 120 140 160 180 200 ICCFL PROGRAMMING CURRENT (A)
LT1186F * G08
Positive DIO Voltage vs Temperature
1.2 1.0 I(DIO) = 5mA 1.6 1.4
Negative DIO Voltage vs Temperature
I(DIO) = 10mA 1.2 1.0 0.8 0.6 0.4 0.2 0 -75 -50 -25 0 25 50 75 100 125 150 175 TEMPERATURE (C)
LT1186F * G12
I(DIO) = 5mA I(DIO) = 1mA
I(DIO) = 1mA
VC Low Clamp Voltage vs Temperature
0.30 0.25 0.20 0.15 0.10 0.05 0 -75 -50 -25 0 25 50 75 100 125 150 175 TEMPERATURE (C)
LT1186F * G14
VC High Clamp Voltage vs Temperature
2.4 2.3 2.2 2.1 2.0 1.9 1.8 1.7 -75 - 50 -25 0 25 50 75 100 125 150 175 TEMPERATURE (C)
LT1186F * G15
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LT1186F TYPICAL PERFORMANCE CHARACTERISTICS
VC Switching Threshold vs Temperature
CCFL VC SWITCHING THRESHOLD VOLTAGE (V)
1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 -75 - 50 -25 0 25 50 75 100 125 150 175 TEMPERATURE (C)
LT1186F * G16
BULB PROTECT SERVO VOLTAGE (V)
7.3 7.2 7.1 7.0 6.9 6.8 6.7 6.6 ICCFL = 10A ICCFL = 50A ICCFL = 100A
BULB INPUT BIAS CURRENT (A)
LT1186F * G17
High-Side Sense Supply Current vs Temperature
CCFL HIGH-SIDE SENSE SUPPLY CURRENT (A) 140 130 120 110 100 90 80 70 60 50 -75 - 50 -25 0 25 50 75 100 125 150 175 TEMPERATURE (C)
LT1186F * G19
CCFL HIGH-SIDE SENSE LINE REGULATI0N (%V)
CCFL HIGH-SIDE SENSE NULL CURRENT (A)
150
VSW Sat Voltage vs Switch Current
1.0 0.9 CCFL VSW CURRENT LIMIT (A)
2.5
CCFL VSW SAT VOLTAGE (V)
0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 0.3 0.9 1.2 0.6 SWITCH CURRENT (A) 1.5 T = 25C T = 125C T = -5C
1.5
FORCED BETA
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LT1186F * G22
BULB Protect Servo Voltage vs Temperature
7.5 7.4 8 10
BULB Input Bias Current vs Temperature
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6.5 -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)
LT1186F * G18
High-Side Sense Null Current vs Temperature
1.060 1.040 1.020 1.000 0.980 0.960 0.940 -75 - 50 -25 0 25 50 75 100 125 150 175 TEMPERATURE (C)
LT1186F * G20
High-Side Sense Null Current Line Regulation vs Temperature
0.160 0.140 0.120 0.100 0.080 0.060 0.040 0.020 0.000 -75 - 50 -25 0 25 50 75 100 125 150 175 TEMPERATURE (C)
LT1186F * G21
VSW Current Limit vs Duty Cycle
110 100 90
Forced Beta vs ISW on VSW
2.0 T = 0C T = 25C T = 125C MINIMUM
80 70 60 50 40 30 20 10 0
1.0
0.5
0 0 10 20 30 40 50 60 DUTY CYCLE (%) 70 80 90
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 CCFL ISW (A)
LT1186F * G24
LT1186F * G23
LT1186F TYPICAL PERFORMANCE CHARACTERISTICS
DAC IOUT vs Temperature
52 VOUT = 0V
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
51 VCC = 5V 50 VCC = 3.3V
49
48 -50
-25
0 25 50 TEMPERATURE (C)
PIN FUNCTIONS
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 regulator provides a separate analog ground and power ground to isolate high current ground paths from low current signal paths. Linear Technology recommends the use of star-ground layout techniques. ICCFL (Pin 2): This pin is the input to the CCFL lamp current programming circuit. This pin internally regulates to 465mV. The pin accepts a DC input current signal of 0A to 50A full scale from the DAC. This input signal is converted to a 0A to 250A source current at the CCFL VC pin. As input programming current increases, the regulated lamp current increases. For a typical 6mA lamp, the range of input programming current is about 0A to 50A. DIO (Pin 3): This pin is the common connection between the cathode and anode of two internal diodes. The remaining terminals of the two diodes connect to ground. In a grounded-lamp configuration, DIO connects to the low voltage side of the lamp. Bidirectional lamp current flows in the DIO pin and thus the diodes conduct alternately on half cycles. Lamp current is controlled by monitoring onehalf of the average lamp current. The diode conducting on negative half cycles has one-tenth of its current diverted to the CCFL VC pin. This current nulls against the source current provided by the lamp-current programmer circuit. A single capacitor on the CCFL VC pin provides both stable loop compensation and an averaging function to the halfwave-rectified sinusoidal lamp current. Therefore, input programming current relates to one-half of average lamp current. This scheme reduces the number of loop compensation components and permits faster loop transient response in comparison to previously published circuits. If a floating lamp configuration is used, ground the DIO pin. CCFL VC (Pin 4): This pin is the output of the lamp current programmer circuit and the input of the current comparator for the CCFL regulator. Its uses include frequency compensation, lamp-current averaging for grounded-lamp circuits and current limiting. The voltage on the CCFL VC pin determines the current trip level for switch turn-off. During normal operation this pin sits at a voltage between 0.95V (zero switch current) and 2.0V (maximum switch current) with respect to analog ground (AGND). This pin has a high impedance output and permits external voltage clamping to adjust current limit. A single capacitor to ground provides stable loop compensation. This simplified loop compensation method permits the CCFL regulator to exhibit single-pole transient response behavior and virtually eliminates transformer output overshoot.
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LT1186F * G25
DAC IOUT vs Supply Voltage
53 52 51 50 49 48 47 46
100 53
DAC IOUT vs IOUT Bias Voltage
52 51 50 49 VCC = 3.3V 48 47 46 VCC = 5V TJ = 25C
VOUT = 0V TJ = 25C
45 0
4 2 6 SUPPLY VOLTAGE (V)
8
LT1186F * G26
45 -20
-15
5 -10 -5 0 OUTPUT BIAS VOLTAGE (V)
10
LT1186F * G27
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LT1186F
PIN FUNCTIONS
AGND (Pin 5): This is the low current analog ground. It is the negative sense terminal for the internal 1.24V reference and the ICCFL summing voltage in the LT1186F. Connect low current signal paths that terminate to ground and frequency compensation components that terminate to ground directly to this pin for best regulation and performance. SHDN (Pin 6): Pulling this pin low causes complete regulator shutdown with quiescent current typically reduced to 35A. If the pin is not used, use a pull-up resistor to force a logic high level (maximum of 6V) or tie directly to VCC. In a shutdown condition, the DAC retains its last output current setting and returns to this level when the logic-low signal at the shutdown pin is removed. CLK (Pin 7): This pin is the shift clock for the DAC. This clock synchronizes the serial data and is a Schmitt trigger input. In standard SPI mode, the clock shifts data into DIN and out of DOUT on the rising and falling edges of the clock respectively. In pulse mode, the rising edge of the clock either increments or decrements the counter. This action depends on the choice of a 1-wire interface (increment only) or a 2-wire interface (increment/decrement). CS (Pin 8): This pin is the chip select input for the DAC. In SPI mode, a logic low on the CS pin enables the DAC to receive and transfer 8-bit serial data. After the serial input data is shifted in, a rising edge of CS transfers the data into the counter, the DAC assumes the new IOUT value and the DOUT pin returns to the high impedance state. On power up, a logic high places the DAC into pulse mode. Pulling CS low after this places the DAC into SPI mode until VCC resets. DIN or UP/DN (Pin 9): This pin is the digital input for the DAC. In SPI mode, the 8-bit serial data is shifted into the DIN input on each rising edge of the clock signal. In pulse mode, on power up, a logic high at DIN transfers the pin function from DIN to UP/DN, puts the counter into increment-only mode and the pin function shifts to up or down increment control of DAC output current. If UP/DN receives a logic-low signal, the counter configures to increment/decrement mode until VCC resets. DOUT (Pin 10): This pin is the digital output for the DAC. In SPI mode, DOUT is in three-state until CS falls low. The DOUT pin then serially transfers the previous 8-bit data on every falling edge of the clock. When CS rises high again, DOUT returns to a three-state condition. In pulse mode, DOUT is always three-stated. IOUT (Pin 11): This pin is the analog current output for the DAC and provides an output current of 50 3A over temperature. This pin can be biased from - 20V to 2V for a 3.3V VCC supply voltage or from - 20V to 2.5V for a 5V VCC supply voltage. However, this pin is tied to the ICCFL pin and provides the programming current which sets operating lamp current. The IOUT pin has very little bias voltage change when it is tied to the ICCFL pin as ICCFL is regulated. The programming current is sourced from the IOUT pin and sunk by the ICCFL pin. VCC (Pin 12): This is the supply pin for the LT1186F. The IC accepts an input voltage range of 3V minimum to 6.5V maximum with little change in quiescent current (zero switch current). An internal, low-dropout regulator provides a 2.4V supply for most of the internal circuitry. Supply current increases as switch current increases at a rate approximately 1/50 of switch current. This corresponds to a forced Beta of 50 for the power switch. The IC incorporates undervoltage lockout by sensing regulator dropout and locking out switching for input voltages below 2.5V. Hysteresis is not used to maximize the useful range of input voltage. The typical input voltage is a 3.3V or 5V logic supply. ROYER (Pin 13): This pin connects to the center-tapped primary of the Royer converter and is used with the BAT pin in a floating-lamp configuration where lamp current is controlled by sensing Royer primary-side converter current. This pin is the inverting terminal of a high-side current sense amplifier. The typical quiescent current is 50A into the pin. If the CCFL regulator is not used in a floating-lamp configuration, tie the Royer and BAT pins together.
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LT1186F
PIN FUNCTIONS
BAT (Pin 14): This pin connects to the battery or AC wall adapter voltage from which the CCFL Royer converter operates. This voltage is typically higher than the VCC supply voltage but can equal VCC if VCC is a 5V logic supply. The BAT voltage must be at least 2.1V greater than the internal 2.4V regulator or 4.5V. This pin provides biasing for the lamp-current programming block, is used with the Royer pin for floating-lamp configurations and connects to one input for the open-lamp protection circuitry. For floating-lamp configurations, this pin is the noninverting terminal of a high-side current sense amplifier. The typical quiescent current is 50A into the pin. The BAT and Royer pins monitor the primary-side Royer converter current through an internal 0.1 topside current sense resistor. A 0A to1A primary-side, center tap converter current is translated to an input signal range of 0mV to 100mV for the current sense amplifier. This input range translates to a 0A to 500A sink current at the CCFL VC pin that nulls against the source current provided by the programmer circuit. The BAT pin also connects to the topside of the internal clamp between the BAT and BULB pins that is used for open-lamp protection. 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. Set the voltage limit to ensure lamp start-up with worst-case, lamp start voltages and cold temperature, system operating conditions. The BULB pin connects to the junction of an external divider network. The divider network connects from the center tap of the Royer transformer or the actual battery supply voltage to the topside of the current source "tail inductor." A capacitor across the top of the divider network filters switching ripple and sets a time constant that determines how quickly the clamp activates. When the comparator activates, sink current is generated to pull the CCFL VC pin down. This action transfers the entire regulator loop from current mode operation into voltage mode operation. CCFL VSW (Pin 16): This pin is the collector of the internal NPN power switch for the CCFL regulator. The power switch provides a minimum of 1.25A. Maximum switch current is a function of duty cycle as internal slope compensation ensures stability with duty cycles greater than 50%. Using a driver loop to automatically adapt base drive current to the minimum required to keep the switch in a quasi-saturation state yields fast switching times and high efficiency operation. The ratio of switch current to driver current is about 50:1.
TEST CIRCUITS
Load Circuit for tDO
1.4V
3k DOUT 100pF
LT1186F * TC01
Load Circuit for tDZ, tDV
3k DOUT 100pF t DZ WAVEFORM 1 5V t DZ WAVEFORM 2, t DV
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Voltage Waveforms for tDO
CLK 0.8V tDO 2.4V DOUT 0.4V
LT1186F * TC03
Voltage Waveforms for tDZ, tDV
CS 0.8V DOUT WAVEFORM 1 (SEE NOTE 1) tDV DOUT WAVEFORM 2 (SEE NOTE 2) 0.4V 90% tDZ 2.0V
2.4V
10%
NOTE 1: WAVEFORM 1 IS FOR AN OUTPUT WITH INTERNAL CONDITIONS SUCH THAT THE OUTPUT IS HIGH UNLESS DISABLED BY CS NOTE 2: WAVEFORM 2 IS FOR AN OUTPUT WITH INTERNAL CONDITIONS SUCH THAT THE OUTPUT IS LOW UNLESS DISABLED BY CS
LT1186F * TC04
LT1186F * TC02
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LT1186F
BLOCK DIAGRAM W
LT1186F DAC Programmable CCFL Switching Regulator
VCC 12 BAT 14 ROYER 13 SHUTDOWN 2.4V REGULATOR UNDERVOLTAGE LOCKOUT THERMAL SHUTDOWN CCFL VSW 16 200kHz OSC R4 0.1 LOGIC DRIVE Q1
SHUTDOWN 6
-
D2 6V R3 1k gm
+
COMP
ANTISAT
+
CURRENT AMP R1 0.125
0A TO 50A FROM IOUT
Q5 1x Q3 2x Q4 5x Q7 9x
Q6 2x
Q11
-
GAIN = 4.4
+
CCFL
Q8 1x Q9 3x D1 Q10 2x
-
V1 0.465V
2 ICCFL
5 AGND
3 DIO
15 BULB
4 CCFL VC
1 CCFL PGND
POWER-ON RESET
LATCH AND LOGIC UP ONLY/ UP/DN LATCH AND LOGIC MODE SELECT 0 = PULSE 1 = SPI
VOLTAGE REFERENCE SHDN
SHDN
8-BIT CURRENT DAC
11 IOUT 50A FULL SCALE
8
CLK 7 DIN 9 CS 8 CONTROL LOGIC
CLK 8-BIT COUNTER/REGISTER UP/DN 8 8
CLK 9-BIT SHIFT REGISTER DO(LSB) Q9 10 DOUT
LT1186F * BD
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LT1186F APPLICATIONS INFORMATION
Introduction Current generation portable computers and instruments use backlit Liquid Crystal Displays (LCDs). Cold Cathode Fluorescent Lamps (CCFLs) provide the highest available efficiency in back lighting 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 conversion in the lamp. The circuit should also permit lamp intensity control from zero to full brightness with no hysteresis or "pop-on." The small size and battery-powered operation associated with LCD equipped apparatus dictate low component count and high efficiency for these circuits. Size constraints place severe limitations on circuit architecture and long battery life is a priority. Laptop and handheld portable computers offer an excellent example. The CCFL and its power supply are responsible for almost 50% of the battery drain. Additionally, all components, including PC board and hardware, usually must fit within the LCD enclosure with a height restriction of 5mm to 10mm. The CCFL regulator drives an inductor that acts as a switched-mode current source for a current-driven Royerclass converter with efficiencies as high as 90%. The control loop forces the CCFL PWM to modulate the average inductor current to maintain constant current in the lamp. The constant current value, and thus lamp intensity, is programmable. This drive technique provides a wide range of intensity control. A unique lamp-current programming block permits either grounded lamp or floating lamp configurations. Grounded lamp circuits directly sense one-half of average lamp current. Floating lamp circuits directly sense the Royer's primary-side converter current. Floating-lamp circuits provide symmetric differential drive to the lamp and reduce the parasitic loss from stray lampto-frame capacitance, extending illumination range. Block Diagram Operation The LT1186F is a fixed frequency, current mode switching regulator. A fixed frequency, current mode switcher controls switch duty cycle directly by switch current rather than by output voltage. Referring to the block diagram for the LT1186F, the switch turns ON at the start of each oscillator cycle. The switch turns OFF when switch current reaches a predetermined level. The control of output lamp current is obtained by using the output of a unique programming block to set current trip level. The current mode switching technique has several advantages. First, it provides excellent rejection of input voltage variations. Second, it reduces the 90 phase shift at mid-frequencies in the energy storage inductor. This simplifies closed-loop frequency compensation under widely varying input voltage or output load conditions. Finally, it allows simple pulse-by-pulse current limiting to provide maximum switch protection under output overload or short-circuit conditions. The LT1186F incorporates a low dropout internal regulator that provides a 2.4V supply for most of the internal circuitry. This low dropout design allows input voltage to vary from 3V to 6.5V with little change in quiescent current. An active low shutdown pin typically reduces total supply current to 35A by shutting off the 2.4V regulator and locks out switching action for standby operation. The IC incorporates undervoltage lockout by sensing regulator dropout and locking out switching below about 2.5V. The regulator also provides thermal shutdown protection that locks out switching in the presence of excessive junction temperatures. A 200kHz oscillator is the basic clock for all internal timing. The oscillator turns on the output switch via its own logic and driver circuitry. Adaptive anti-sat circuitry detects the onset of saturation in the power switch and adjusts base drive current instantaneously to limit switch saturation. This minimizes driver dissipation and provides rapid turnoff of the switch. The CCFL power switch is guaranteed to provide a minimum of 1.25A in the LT1186F. The anti-sat
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LT1186F APPLICATIONS INFORMATION
circuitry provides a ratio of switch current to driver current of about 50:1. 8-Bit Current Output DAC The 8-bit current output DAC is guaranteed monotonic and is digitally adjustable by the 8-bit counter in 256 equal steps. On power up, the counter resets to 80H and the DAC assumes its mid-range value. The current output IOUT drives the ICCFL pin and sets control current for the lamp current programming block. The DAC has its own 1.24V bandgap reference and a voltage to current converter that is trimmed at wafer sort to provide the precision full-scale current reference. Over temperature, the current output of the DAC is 50A 6%. Digital Interface On power-up, a logic high at CS configures the DAC into pulse mode. If CS is ever pulled low, the chip configures into SPI mode until VCC resets. On power-up in pulse mode, a logic high at DIN puts the counter into incrementonly mode. If UP/DN (DIN) is ever pulled low, the counter configures into increment/decrement mode until VCC resets. These modes are illustrated in Figure 1.
SINGLE DAC CS EVER GOES LOW CS STAYS HIGH
SPI MODE DIN (UP/DN) EVER GOES LOW
PULSE MODE DIN STAYS HIGH
INCREMENT/ DECREMENT
INCREMENTONLY
LT1186F * F01a
Figure 1a. Tree Diagram (LT1186F DAC Operating Modes)
POWER ON VCC
CS CS EVER GOES LOW
LT1186F * F01b
Figure 1b. SPI Mode Setup
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POWER ON VCC
CS ALWAYS HIGH
DIN ALWAYS HIGH
LT1186F * F01c
Figure 1c. Pulse Mode Setup (Increment Only)
POWER ON VCC
CS ALWAYS HIGH
UP/DN UP/DN EVER GOES LOW
LT1186F * F01d
Figure 1d. Pulse Mode Setup (Increment/Decrement)
Standard SPI Mode Refer to the serial interface operating sequence in Figure 2. A falling edge at CS initiates the data transfer. After the falling CS is recognized, DOUT comes out of three-state. The clock (CLK) synchronizes the data transfer. Each input bit shifts into DIN beginning with the MSB on the rising CLK edge and each previous data bit shifts out of DOUT beginning with the MSB on the falling CLK edge. After the 8-bit serial input data is shifted in, a rising edge at CS transfers the data into the counter, the DAC assumes the new value IOUT = (8-bit serial input data)(50A)/255 and the DOUT pin returns to a high impedance state. 1-Wire Interface (Pulse Mode) In increment-only pulse mode, each rising edge of CLK increments the upper six bits of the counter by one count. When incremented beyond 11111100B, the counter rolls over and sets the DAC to the minimum value 00000000B. Therefore, a single pulse applied to CLK increases the upper 6-bit counter by one-step, and 63 pulse applied to CLK decreases the counter by one-step. The last two LSBs are always zero in this mode. IOUT = (B7B6B5B4B3B2B1B0) (50A)/255. The upper 6-bit counter = B7B6B5B4B3B2 and B1 = B0 = 0. To configure the LT1186F into increment-only mode, tie CS and DIN to VCC.
LT1186F APPLICATIONS INFORMATION
tCSLO CS tCKS CLK tCSS DIN D7 tDV DOUT Hi-Z D7 D6 D5 D4 D3 D6 D5 tDS D4 tDH D3 tDO D2 D1 D0 D2 D1 tCKLO D0 tDZ D7 Hi-Z
LT1186F * F02
Figure 2. SPI Interface Timing Specification
2-Wire Interface (Pulse Mode) In increment/decrement pulse mode, a logic high at UP/ DN programs the counter into increment mode and each rising edge of CLK increments the upper six bits of the counter by one. The counter stops incrementing at 11111100B. A logic low at UP/DN programs the counter into decrement mode and each rising edge of CLK decrements the upper six bits of the counter by one. The counter stops decrementing at 00000000B. The last two LSBs are always zero in this mode. IOUT = (B7B6B5B4B3B2B1B0) (50A)/255. The upper 6-bit counter = B7B6B5B4B3B2 and B1 = B0 = 0. To configure the LT1186F into increment/ decrement mode, tie CS to VCC and pulse the UP/DN pin once on power-up. Simplified Lamp Current Programming A programming block in the LT1186F controls lamp current, permitting either grounded lamp or floating lamp configurations. Grounded configurations control lamp current by directly controlling one-half of actual lamp current and converting it to a feedback signal to close a control loop. Floating configurations control lamp current by directly controlling the Royer's primary-side converter current and generating a feedback signal to close a control loop. Previous backlighting solutions have used a traditional error amplifier in the control loop to regulate lamp current. This approach converted an RMS current into a DC voltage for the input of the error amplifier. This approach used several time constants in order to provide stable loop
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tCSHI
tCKHI
tCSH
tCKH
frequency compensation. This compensation scheme meant that the loop had to be fairly slow and that output overshoot with start-up or overload conditions had to be carefully evaluated in terms of transformer stress and breakdown voltage requirements. The LT1186F eliminates the error amplifier concept entirely and replaces it with a lamp current programming block. This block provides an easy-to-use interface to program lamp current. The programmer circuit also reduces the number of time constants in the control loop by combining the error signal conversion scheme and frequency compensation into a single capacitor. The control loop thus exhibits the response of a single pole system, allows for faster loop transient response and virtually eliminates overshoot under start-up or overload conditions. Lamp current is programmed at the input of the programmer block, the ICCFL pin. This pin is the input of a shunt regulator and accepts a DC input current signal of 0A to 50A from the DAC. This input signal is converted to a 0A to 250A source current at the CCFL VC pin. The programmer circuit is simply a current-to-current converter with a gain of five. The typical input current programming range for 0mA to 6mA lamp current is 0A to 50A. The ICCFL pin is sensitive to capacitive loading and will oscillate with capacitance greater than 10pF. For example, loading the ICCFL pin with a 1x or 10x scope probe causes oscillation and erratic CCFL regulator operation because of the probe's respective input capacitance. A current meter in series with the ICCFL pin will also produce oscil-
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LT1186F APPLICATIONS INFORMATION
lation due to its shunt capacitance. Use a decoupling resistor of several kilohms between the ICCFL pin and the IOUT pin if excessive trace stray capacitance exists. Normally, this resistor is not required. In some applications, the maximum programming current required at the ICCFL pin for a maximum lamp current will be less than the full-scale output current of the DAC, which is 50A. The system designer can either limit the maximum programming current through software built into the system, or use a current splitter which shunts a percentage of the fullscale current from the ICCFL pin. A splitter circuit is illustrated in Figure 3. A divider string is used from a reference voltage to set up a voltage level equal to the ICCFL summing voltage, or 465mV. The main current flowing in the divider string should be chosen to swamp out the effects of the shunted current into the divider string.
IOUT FULL-SCALE 50A I V1 R1 XI R2 (1 - X)I I1 V(ICCFL) 465mV VREF R3 V(ICCFL) R4 I = 50A 0> (1 - X)I R1 = (V1 - 0.465)/(X)(50A) R2 = (V1 - 0.465)/(1 - X)(50A) R3 = (VREF - 0.465)/I1 R4 = 0.465R3/[(1 - X) 50AR3 + (VREF - 0.465)] LT1186F * F03
Figure 3
Grounded Lamp Configuration In a grounded lamp configuration, the low voltage side of the lamp connects directly to the LT1186F DIO pin. This pin is the common connection between the cathode and anode of two internal diodes. In previous grounded lamp solutions, these diodes were discrete units and are now integrated onto the IC, saving cost and board space. Bidirectional lamp current flows in the DIO pin and thus, the diodes conduct alternately on half 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. Therefore, input programming current relates to one-half of average lamp current.
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The transfer function between lamp current and input programming current must be empirically determined and is dependent on the particular lamp/display housing combination used. The lamp and display housing are a distributed loss structure due to parasitic lamp-to-frame capacitance. This means that the current flowing at the highvoltage side of the lamp is higher than what is flowing at the DIO pin side of the lamp. The input programming current is set to control lamp current at the high-voltage side of the lamp, even though the feedback signal is the lamp current at the bottom of the lamp. This ensures that the lamp is not overdriven which can degrade the lamp's operating lifetime. Therefore, the full scale current of the DAC does not necessarily correspond to the current required to set maximum lamp current. Floating Lamp Configuration In a floating lamp configuration, the lamp is fully floating with no galvanic connection to ground. This allows the transformer to provide symmetric differential drive to the lamp. Balanced drive eliminates the field imbalance associated with parasitic lamp-to-frame capacitance and reduces "thermometering" (uneven lamp intensity along the lamp length) at low lamp currents. Carefully evaluate display designs in relation to the physical layout of the lamp, its leads and the construction of the display housing. Parasitic capacitance from any high voltage point to DC or AC ground creates paths for unwanted current flow. This parasitic current flow degrades electrical efficiency and losses up to 25% have been observed in practice. As an example, at a Royer operating frequency of 60kHz, 1pF of stray capacitance represents an impedance of 2.65M. With an operating lamp voltage of 400V and an operating lamp current of 6mA, the parasitic current is 150A. This additional current must be supplied by the transformer secondary. Layout techniques that increase parasitic capacitance include long high voltage lamp leads, reflective metal foil around the lamp and displays supplied in metal enclosures. Losses for a good display are under 5%, whereas, losses for a bad display range from 5% to 25%. Lossy displays are the primary reason to use a floating lamp configuration. Providing symmetric, differential drive to the lamp reduces the total parasitic loss by one-half.
LT1186F APPLICATIONS INFORMATION
Maintaining closed-loop control of lamp current in a floating lamp configuration necessitates deriving a feedback signal from the primary side of the Royer transformer. Previous solutions have used an external precision shunt and high-side sense amplifier configuration. This approach has been integrated onto the LT1186F for simplicity of design and ease of use. An internal 0.1 resistor monitors the Royer converter current and connects between the input terminals of a high-side sense amplifier. A 0 - 1 Amp Royer primary-side, center-tap current is translated to a 0A to 500A sink current at the CCFL VC pin to null 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 error sink current. Therefore, input programming current is related to average Royer converter current. Floating lamp circuits operate similarly to grounded lamp circuits except for the derivation of the feedback signal. The transfer function between lamp current and input programming current must be empirically determined and is dependent upon a myriad of factors including lamp characteristics, display construction, transformer turns ratio and the tuning of the Royer oscillator. Once again, lamp current will be slightly higher at one end of the lamp and input programming current should be set for this higher level to ensure that the lamp is not overdriven. The internal 0.1 high-side sense resistor on the LT1186F is rated for a maximum DC current of 1A. This resistor can be damaged by extremely high surge currents at start-up. The Royer converter typically uses a few microfarads of bypass capacitance at the center tap of the transformer. This capacitor charges up when the system is first powered by the battery pack or an AC wall adapter. The amount of current delivered at start-up can be 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 0.5. 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. This issue only exists with floating lamp circuits as grounded lamp circuits do not make use of the high-side sense resistor. Input Capacitor Type Caution must be used in selecting the input capacitor type for switching regulators. Aluminum electrolytics are electrically rugged and the lowest cost, but are physically large to meet required ripple current ratings, and size constraints (especially height) may preclude their use. Ceramic capacitors are now available in larger values and their high ripple current and voltage rating make them ideal for input bypassing. Cost is fairly high and footprint can be large. Solid tantalum capacitors would be a good choice except for a history of occasional failure when subjected to large current surges during start-up. The input bypass capacitor of regulators can see these high surges when a battery or high capacitance source is connected. Some manufacturers have developed tantalum capacitor lines specially tested for surge capability (AVX TPS series for instance), but even these units may fail if the input voltage surge approaches the capacitor's maximum voltage rating. AVX recommends derating the capacitor voltage by 2:1 for high surge applications. Applications Support Linear Technology invests an enormous amount of time, resources and technical expertise in understanding, designing and evaluating backlight/LCD contrast solutions for system designers. The design of an efficient and compact LCD backlight system is a study of compromise in a transduced electronic system. Every aspect of the design is interrelated and any design change requires complete re-evaluation for all other critical design parameters. Linear Technology has engineered one of the most complete test and evaluation setups for backlight designs and understands the issues and tradeoffs in achieving a compact, efficient and economical customer solution. Linear Technology welcomes the opportunity to discuss, design, evaluate and optimize any backlight/LCD contrast system with a customer. For further information on backlight/LCD contrast designs, consult the References.
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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LT1186F APPLICATIONS INFORMATION
References 1. Williams, Jim. August 1992. Illumination Circuitry for Liquid Crystal Displays. Linear Technology Corporation, Application Note 49. 2. Williams, Jim. August 1993. Techniques for 92% Efficient LCD Illumination. Linear Technology Corporation, Application Note 55. 3. Bonte, Anthony. March 1995. LT1182 Floating CCFL with Dual Polarity Contrast. Linear Technology Corporation, Design Note 99. 4. Williams, Jim. April 1995. A Precision Wideband Current Probe for LCD Backlight Measurement. Linear Technology Corporation, Design Note 101. 5. LT1182/LT1183/LT1184/LT1184F Data Sheet. CCFL/ LCD Contrast Switching Regulators. April 1995. Linear Technology Corporation.
PACKAGE DESCRIPTION
Dimensions in inches (millimeters) unless otherwise noted.
S Package 16-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.386 - 0.394* (9.804 - 10.008) 0.010 - 0.020 x 45 (0.254 - 0.508) 0.008 - 0.010 (0.203 - 0.254) 0.053 - 0.069 (1.346 - 1.752) 0 - 8 TYP 0.228 - 0.244 (5.791 - 6.197) 0.150 - 0.157** (3.810 - 3.988) 0.004 - 0.010 (0.101 - 0.254) 16 15 14 13 12 11 10 9
0.016 - 0.050 0.406 - 1.270
0.014 - 0.019 (0.355 - 0.483)
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
RELATED PARTS
PART NUMBER LT1107 LT1172 LT1173 LT1182 LT1183 LT1184 LT1184F LT1372 DESCRIPTION Micropower DC/DC Converter for LCD Contrast Control Current Mode Switching Regulator for CCFL or LCD Contrast Control Micropower DC/DC Converter for LCD Contrast Control Dual Current Mode Switching Regulator for CCFL and LCD Contrast Control Dual Current Mode Switching Regulator for CCFL and LCD Contrast Control Current Mode Switching Regulator for CCFL Control Current Mode Switching Regulator for CCFL Control Current Mode Switching Regulator for CCFL or LCD Contrast Contol COMMENTS 1A, 63kHz, Hysteretic 1.25A, 100kHz 1A, 24kHz, Hysteretic 1.25A, 0.625A, 200kHz 1.25A, 0.625A, 200kHz 1.25A, 200kHz 1.25A, 200kHz 1.5A, 500kHz
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 q FAX: (408) 434-0507 q TELEX: 499-3977
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0.050 (1.270) TYP
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S16 0695
LT/GP 1096 7K REV A * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 1995

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