LINEAR TECHNOLOGY LT3466-1 Technical data

FEATURES

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■

Drives Up to 10 White LEDs from a 3.6V Supply

■

Two Independent Step-Up DC/DC Converters

■

Independent Dimming and Shutdown Control
of the Outputs

■

±1.5% Output Voltage Accuracy (Boost Converter)

■

±4% LED Current Programming Accuracy

■

Internal Schottky Diodes

■

Internal Soft-Start Eliminates Inrush Current

■

Output Overvoltage Protection (39.5V Max V

■

Fixed Frequency Operation Up to 2MHz

■

83% Efficiency Driving 8 White LEDs at 15mA

OUT

from a 3.6V Supply

■

Wide Input Voltage Range: 2.7V to 24V

■

Tiny (3mm × 3mm) 10-Lead DFN Package

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APPLICATIO S

■

White LED and OLED Displays

■

Digital Cameras, Sub-Notebook PCs

■

PDAs, Handheld Computers

■

TFT - LCD Bias Supply

■

Automotive

LT3466-1

White LED Driver and Boost

Converter in 3mm × 3mm

DFN Package

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DESCRIPTIO

LT®3466-1 is a dual switching regulator that combines a
white LED driver and a boost converter in a low profile,
small footprint (3mm × 3mm × 0.75mm) DFN package.
The LED driver can be configured to drive up to 10 White
LEDs in series and the boost converter can be used for
generating the LCD bias voltages or driving a secondary
OLED display. Series connection of the LEDs provides
identical LED currents resulting in uniform brightness and

)

eliminating the need for ballast resistors and expensive
factory calibration.

The LT3466-1 provides independent dimming and shut­down control of the two converters. The operating fre­quency can be set with an external resistor over a 200kHz
to 2MHz range. The white LED driver features a low 200mV
reference, thereby minimizing power loss in the current
setting resistor for better efficiency. The boost converter
achieves ±1.5% output voltage accuracy by the use of a
precision 0.8V reference. Protection features include out­put overvoltage protection and internal soft-start. Wide
input supply range allows operation from 2.7V to 24V.

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

All other trademarks are the property of their respective owners.

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TYPICAL APPLICATIO

3V TO 5V

1µF

IN

LT3466-1

R

T

33µH

V

SHUTDOWN
AND DIMMING
CONTROL 2

OUT2

FB2

16V
30mA

475k

24.9k

34661 F01a

6 LEDs

33µH

SW1 SW2V

V

1µF1µF

10Ω

OUT1

FB1

CTRL1 GND CTRL2

SHUTDOWN

AND DIMMING

CONTROL 1

63.4k

Figure 1. Li-Ion Powered Driver for 6 White LEDs and OLED Display

90

VIN = 3.6V

85

LED DRIVER

80

75

70

65

EFFICIENCY (%)

60

55

50

0

Conversion Efficiency

BOOST CONVERTER

51015

OUTPUT CURRENT (mA)

302520

34661 F01b

34661f

1

LT3466-1

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WWWU

ABSOLUTE AXI U RATI GS

PACKAGE/ORDER I FOR ATIO

UU

W

(Note 1)

Input Voltage (VIN) ................................................... 24V

SW1, SW2 Voltages ................................................ 44V

V

OUT1

, V

Voltages ............................................. 44V

OUT2

CTRL1, CTRL2 Voltages ........................................... 24V

FB1, FB2 Voltages ...................................................... 2V

Operating Temperature Range (Note 2) ... –40°C to 85°C

Storage Temperature Range .................. –65°C to 125°C

Junction Temperature .......................................... 125°C

ELECTRICAL CHARACTERISTICS

range, otherwise specifications are at TA = 25°C. VIN = 3V, V

PARAMETER CONDITIONS MIN TYP MAX UNITS

Minimum Operating Voltage 2.7 V

Maximum Operating Voltage 22 V

FB1 Voltage ● 192 200 208 mV

FB2 Voltage ● 788 800 812 mV

FB1 Pin Bias Current V

FB2 Pin Bias Current V

Quiescent Current V

Switching Frequency RT = 48.7k 0.75 1 1.25 MHz

Oscillator Frequency Range (Note 4) 200 2000 kHz

Nominal RT Pin Voltage RT = 48.7k 0.54 V

Maximum Duty Cycle RT = 48.7k ● 90 96 %

Converter 1 Current Limit ● 310 400 mA

Converter 2 Current Limit ● 310 400 mA

Converter 1 V

Converter 2 V

Switch 1 Leakage Current V

Switch 2 Leakage Current V

CTRL1 Voltage for Full LED Current ● 1.8 V

CTRL2 Voltage for Full Feedback Voltage ● 1V

CTRL1 or CTRL2 Voltage to Turn On the IC 150 mV

CTRL1 and CTRL2 Voltages to Shut Down Chip 70 mV

CTRL1 Pin Bias Current V

CTRL2 Pin Bias Current V

CESAT

CESAT

FB1

FB2

FB1

CTRL1 = CTRL2 = 0V 16 25 µA

R

= 20.5k 92 %

T

RT = 267k 99 %

I

SW1

I

SW2

SW1

SW2

CTRL1

CTRL2

The ● denotes specifications that apply over the full operating temperature

= 3V, V

CTRL1

= 0.2V (Note 3) 10 50 nA

= 0.8V (Note 3) 10 50 nA

= V

= 1V 5 7.5 mA

FB2

= 300mA 320 mV

= 300mA 320 mV

= 10V 0.01 5 µA

= 10V 0.01 5 µA

= 1V ● 6 9 12.5 µA

= 1V (Note 3) ● 10 120 nA

V

OUT1

SW1

V

IN

SW2

V

OUT2

10-LEAD (3mm × 3mm) PLASTIC DFN

T

JMAX

Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF

Lead Free Part Marking: http://www.linear.com/leadfree/

Consult LTC Marketing for parts specified with wider operating temperature ranges.

CTRL2

TOP VIEW

10

9

8

7

6

FB1

CTRL1

R

T

CTRL2

FB2

DD PART MARKING

1

2

11

3

4

5

DD PACKAGE

= 125°C, θJA = 43°C/W, θJC = 3°C/W

EXPOSED PAD (PIN 11) IS GND

MUST BE SOLDERED TO PCB

= 3V, unless otherwise specified.

ORDER PART

NUMBER

LT3466EDD-1

LBRX

34661f

2

LT3466-1

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ELECTRICAL CHARACTERISTICS

range, otherwise specifications are at TA = 25°C. VIN = 3V, V

The ● denotes specifications that apply over the full operating temperature

CTRL1

= 3V, V

= 3V, unless otherwise specified.

CTRL2

PARAMETER CONDITIONS MIN TYP MAX UNITS

V

Overvoltage Threshold 39.5 V

OUT1

V

Overvoltage Threshold 39.5 V

OUT2

Schottky 1 Forward Drop I

Schottky 2 Forward Drop I

Schottky 1 Reverse Leakage V

Schottky 2 Reverse Leakage V

SCHOTTKY1

SCHOTTKY2

OUT1

OUT2

= 300mA 0.85 V

= 300mA 0.85 V

= 20V 5 µA

= 20V 5 µA

Soft-Start Time (Switcher 1) 600 µs

Soft-Start Time (Switcher 2) 600 µs

Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.

Note 3: Current flows out of the pin.
Note 4: Guaranteed by design and test correlation, not production tested.

Note 2: The LTC3466-1E is guaranteed to meet specified performance

from 0°C to 70°C. Specifications over the –40°C to 85°C operating range
are assured by design, characterization and correlation with statistical
process controls.

UW

TYPICAL PERFOR A CE CHARACTERISTICS

TA = 25°C unless otherwise specified

V

OUT1

100mV/DIV

(AC-COUPLED)

V

SW1

20V/DIV

I

100mA/DIV

250

200

150

(mV)

FB1

V

100

Switching Waveforms
(LED Driver)

L1

V

= 3.6V 0.5µs/DIV 34661 G01

IN

6 LEDs AT 20mA
CIRCUIT OF FIGURE 1

V

vs V

50

0

0

FB1

VIN = 3.6V
6 LEDs

0.5

CTRL1

V

CTRL1

1

(V)

1.5

34661 G03

Switching Waveforms
(Boost Converter)

V

OUT2

100mV/DIV

(AC-COUPLED)

V

SW2

20V/DIV

I

L2

100mA/DIV

VIN = 3.6V 0.5µs/DIV 34661 G02
V

= 16V/30mA

OUT2

CIRCUIT OF FIGURE 1

V

vs V

FB2

900

VIN = 3.6V
V

800

700

600

500

(mV)

FB2

400

V

300

200

100

2

0

0

OUT2

= 16V

0.5

CTRL2

V

CTRL2

1

(V)

1.5

34661 G16

2

34661f

3

LT3466-1

VIN (V)

2

0

SHUTDOWN CURRENT (µA)

10

30

40

50

70

4

12

16

34661 G06

20

60

10

20

2422

6

8

14 18

TA = –50°C

TA = 25°C

TA = 100°C

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TYPICAL PERFOR A CE CHARACTERISTICS

TA = 25°C unless otherwise specified

500

450

400

350

300

250

200

150

CURRENT LIMIT (mA)

100

50

0

0

TA = –50°C

T

A

20

DUTY CYCLE (%)

= 85°C

40

Open-Circuit Output Clamp
Voltage

41.00
RT = 63.4k

40.50

40.00

39.50

39.00

OUTPUT CLAMP VOLTAGE (V)

38.50

V

V

OUT2

OUT1

60

TA = 25°C

80

34661 G05

100

Quiescent Current
(CTRL1 = CTRL2 = 3V)Switch Current Limit vs Duty Cycle

7

0

UVLO

48

VIN (V)

12 20

6

5

4

3

2

QUIESCENT CURRENT (mA)

1

0

Open-Circuit Output Clamp
Voltage

42

RT = 63.4k

41

40

39

38

OUTPUT CLAMP VOLTAGE (V)

16 24

V

OUT2

V

OUT1

34661 G04

Shutdown Current
(CTRL1 = CTRL2 = 0V)

Input Current with Output 1 and
Output 2 Open Circuit

20

RT = 63.4k

16

12

8

INPUT CURRENT (mA)

4

38.00

6 101418

VIN (V)

2442 8 12 16 20 22

34661 G07

37

–50 –25

0

TEMPERATURE (°C)

RT vs Oscillator Frequency

1000

100

4

(kΩ)

T

R

10

600 180014001000

200

OSCILLATOR FREQUENCY (kHz)

34661 G10

50

25

75

100

Oscillator Frequency vs V

1100

RT = 48.7k

1000

900

OSCILLATOR FREQUENCY (kHz)

800

VIN (V)

0

2

125

34661 G08

8121620

468

IN

34661 G11

10 12

24462 10141822

14 16 20

VIN (V)

18

2422

34661 G09

34661f

UW

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TYPICAL PERFOR A CE CHARACTERISTICS

LT3466-1

TA = 25°C unless otherwise specified

Oscillator Frequency
vs Temperature

1100

VIN = 3.6V

= 48.7k

R

T

1000

900

OSCILLATOR FREQUENCY (kHz)

800

–50

–25 0 25 50

TEMPERATURE (°C)

75

100

34661 G12

CTRL Voltages to Shut Down
the IC

150

= 3.6V

V

IN

125

100

75

50

CTRL VOLTAGE (mV)

25

0

–50

CTRL1

02550

–25

TEMPERATURE (°C)

CTRL2

Schottky Forward Voltage Drop Schottky Leakage Current

400

350

300

250

200

150

100

50

SCHOTTKY FORWARD CURRENT (mA)

0

200 400 800

0

SCHOTTKY FORWARD DROP (mV)

600

1000

34661 G14

8

6

4

2

SCHOTTKY LEAKAGE CURRENT (µA)

0

–50

–25 0 25 50

TEMPERATURE (°C)

75 100

34661 G13

VR = 36V

VR = 20V

75 100

34661 G015

FB2 Pin Voltage vs Temperature

0.810
VIN = 3V

= 16V/30mA

V

OUT2

0.805

0.800

0.795

FB2 VOLTAGE (V)

0.790

0.785

0.780

–50

02550

–25

TEMPERATURE (°C)

75 125100

34661 G17

FB2 Pin Load Regulation

0

–0.20

(%)

–0.40

OUT2

/V

–0.60

OUT2

∆V

–0.80

–1.00

0

10 20

LOAD CURRENT (mA)

V
V

IN
OUT2

= 3V

= 16V

30

34661 G18

34661f

5

LT3466-1

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PI FU CTIO S

V

(Pin 1): Output of Converter 1. This pin is connected

OUT1

to the cathode of the internal Schottky diode. Connect an
output capacitor from this pin to ground.

SW1 (Pin 2): Switch Pin for Converter 1. Connect the
inductor at this pin.

VIN (Pin 3): Input Supply Pin. Must be locally bypassed
with a 1µF, X5R or X7R type ceramic capacitor.

SW2 (Pin 4): Switch Pin for Converter 2. Connect the
inductor at this pin.

V

(Pin 5): Output of Converter 2. This pin is connected

OUT2

to the cathode of the internal Schottky diode. Connect an
output capacitor from this pin to ground.

FB2 (Pin 6): Feedback Pin for Converter 2. The nominal
voltage at this pin is 800mV. Connect the resistor divider
to this pin. The feedback voltage can be programmed
as:

V

≈ V

FB2

V

= 0.8V, when V

FB2

CTRL2

, when V

CTRL2

CTRL2

> 1V

< 0.8V

CTRL2 (Pin 7): Dimming and Shutdown Pin for Con­verter 2. As the pin voltage is ramped from 0V to 1V, the
FB2 pin voltage tracks the CTRL2 voltage and ramps up to

0.8V. Any voltage above 1V does not affect the feedback
voltage. Do not leave the pin floating. It must be connected
to ground to disable converter 2.

RT (Pin 8): Timing Resistor to Program the Switching
Frequency. The switching frequency can be programmed
from 200KHz to 2MHz.

CTRL1 (Pin 9): Dimming and Shutdown Pin for Con­verter 1. Connect this pin to ground to disable the con­verter. As the pin voltage is ramped from 0V to 1.8V, the
LED current ramps from 0 to I
voltage above 1.8V does not affect the LED current.

FB1 (Pin 10): Feedback Pin for Converter 1. The nominal
voltage at this pin is 200mV. Connect cathode of the lowest
LED and the feedback resistor at this pin. The LED current
can be programmed by :

I

≈ (V

LED1

I

≈ (200mV/R

LED1

CTRL1

/5 • R

FB1

), when V

FB1

), when V

(= 200mV/R

LED1

CTRL1

CTRL1

< 1V

> 1.8V

FB1

). Any

Exposed Pad (Pin 11): The Exposed Pad must be soldered
to the PCB system ground.

6

34661f