Linear Technology LT3591EDDB, LT3591 Datasheet

LT3591

1

3591f

■

Cellular Phones

■

PDAs, Handheld Computers

■

Digital Cameras

■

MP3 Players

■

GPS Receivers

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

White LED Driver with

Integrated Schottky in

3mm × 2mm DFN

The LT®3591 is a fi xed frequency step-up DC/DC converter
specifi cally designed to drive up to ten white LEDs in series
from a Li-Ion cell. Series connection of the LEDs provides
identical LED currents resulting in uniform brightness
and eliminating the need for ballast resistors. The device
features a unique high side LED current sense that enables
the part to function as a “one wire current source;” one
side of the LED string can be returned to ground anywhere,
allowing a simpler one wire LED connection. Traditional
LED drivers use a grounded resistor to sense LED current,
requiring a 2-wire connection to the LED string.

The high switching frequency allows the use of tiny induc­tors and capacitors. A single pin performs both shutdown
and accurate LED dimming control. Few external compo­nents are needed: open-LED protection and the Schottky
diode are all contained inside a low profi le 3mm × 2mm
DFN package.

Li-Ion Driver for Ten White LEDs

■

Drives Up to Ten White LEDs from a 3V Supply

■

High Side Sense Allows “One Wire Current Source”

■

Internal Schottky Diode

■

One Pin Dimming and Shutdown

■

80:1 True Color PWMTM Dimming Range

■

42V Open LED Protection

■

1MHz Switching Frequency

■

±5% Reference Accuracy

■

VIN Range: 2.5V to 12V

■

Requires Only 2.2µF Output Capacitor

■

Low Profi le 8-Lead DFN Package

(3mm × 2mm × 0.75mm)

Conversion Effi ciency

CTRL

V

IN

22µH

V

IN

3V TO 5V

R

SENSE

10Ω

3591 TA01a

LT3591

SHUTDOWN AND

DIMMING CONTROL

SW

CAP

LED

GND

2.2µF

1µF

LED CURRENT (mA)

0

EFFICIENCY (%)

60

20

3591 TA01b

5

10

15

80

70

55

65

75

VIN = 3.6V
10 LEDs

, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
True Color PWM is a trademark of Linear Technology Corporation. All other trademarks are
the property of their respective owners.

LT3591

2

3591f

PACKAGE/ORDER INFORMATION

ELECTRICAL CHARACTERISTICS

ABSOLUTE MAXIMUM RATINGS

Input Voltage (VIN) ................................................... 12V

CTRL Voltage ........................................................... 12V

SW Voltage .............................................................. 45V

CAP Voltage ............................................................. 45V

LED Voltage ............................................................. 45V

Operating Junction Temperature Range

(Note 2) ...............................................–40°C to 85°C

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

Storage Temperature Range ...................–65°C to 150°C

(Note 1)

Note 1: Stresses beyond those listed under Absolute Maximum Ratings

may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.

PARAMETER CONDITIONS MIN TYP MAX UNITS

Minimum Operating Voltage

2.5 V

LED Current Sense Voltage (V

CAP

– V

LED

)V

CAP

= 24V, ISW = 300mA

●

190 200 210 mV

CAP Pin Bias Current V

CAP

= 36V, V

LED

= 35.8V

40 80 µA

LED Pin Bias Current V

CAP

= 36V, V

LED

= 35.8V 20 40 µA

Supply Current V

CAP

= 24V, V

LED

= 23V

CTRL = 0V

4
9

5

11

mA

µA

Switching Frequency 0.75 1 1.2 MHz

Maximum Duty Cycle 92 94 %

Switch Current Limit

●

500 800 mA

Switch V

CESAT

ISW = 300mA 200 mV

Switch Leakage Current V

SW

= 24V 0.1 5 µA

V

CTRL

for Full LED Current V

CAP

= 44V

●

1.5 V

V

CTRL

to Shut Down IC 50 mV

V

CTRL

to Turn On IC

●

100 mV

CTRL Pin Bias Current 100 nA

CAP Pin Overvoltage Protection

●

40 42 44 V

Schottky Forward Drop I

SCHOTTKY

= 200mA 0.8 V

Schottky Leakage Current V

R

= 30V 4 µA

TOP VIEW

9

DDB PACKAGE

8-LEAD (3mm × 2mm) PLASTIC DFN

5

6

7

8

4

3

2

1V

IN

GND

NC

SW

CTRL

LED

NC

CAP

T

JMAX

= 125°C, θJA = 76°C/W

EXPOSED PAD (PIN 9) SHOULD BE CONNECTED TO PCB GROUND

ORDER PART NUMBER DDB PART MARKING

LT3591EDDB LCPG

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 specifi ed with wider operating temperature ranges.

The

●

denotes the specifi cations which apply over the full operating

temperature range, otherwise specifi cations are at T

A

= 25°C. VIN = 3V, V

CTRL

= 3V, unless otherwise specifi ed.

Note 2: The LT3591E is guaranteed to meet performance specifi cations

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

LT3591

3

3591f

TYPICAL PERFORMANCE CHARACTERISTICS

Switch Saturation Voltage
(V

CESAT

)

Schottky Forward Voltage Drop

Shutdown Current (V

CTRL

= 0V)

Sense Voltage (V

CAP

– V

LED

)

vs V

CTRL

Open-Circuit Output
Clamp Voltage

Input Current in Output
Open Circuit

Switching Waveform

Transient Response

SWITCH CURRENT (mA)

0

500

400

300

200

100

0

300 600

3591 G01

100 200

400 800700

500

SWITCH SATURATION VOLTAGE (mV)

–50°C

125°C

25°C

SCHOTTKY FORWARD DROP (mV)

SCHOTTKY FORWARD CURRENT (mA)

200

300

3591 G02

100

0

600

500

400

0 200 400 600 800

1000 1200

–50°C

125°C

25°C

VIN (V)

0

SHUTDOWN CURRENT (µA)

9

12

15

12

3591 G03

6

3

0

3

6

9

–50°C

125°C

25°C

V

CTRL

(mV)

SENSE VOLTAGE (mV)

80

120

3591 G04

40

0

240

200

160

0 500 1000 1500 2000 2500 3000

–50°C
25°C
125°C

VIN (V)

0

OUTPUT CLAMP VOLTAGE (V)

42

43

12

3591 G05

41

40

3

6

9

45

44

–50°C

125°C

25°C

VIN (V)

0

INPUT CURRENT (mA)

36 912

3591 G06

–50°C

125°C

4

5

6

3

2

0

1

8

7

25°C

V

SW

20V/DIV

V

CAP

50mV/DIV

I

L

200mA/DIV

V

IN

= 3.6V
FRONT PAGE
APPLICATION CIRCUIT

500ms/DIV

3591 G07

V

CTRL

5V/DIV

V

CAP

5V/DIV

I

L

500mA/DIV

V

IN

= 3.6V
FRONT PAGE
APPLICATION CIRCUIT

1ms/DIV

3591 G08

TA = 25°C, unless otherwise specifi ed.

LT3591

4

3591f

VIN (V)

0

0

QUIESCENT CURRENT (mA)

1

2

3

4

5

6

36 912

3591 G09

–50°C

125°C

25°C

TEMPERATURE (°C)

0

CURRENT LIMIT (mA)

400

1000

3591 G10

200

600

800

–50 –25 0 25 50 75 100 125

–50 25 75

–25 0

50 100 125

TEMPERATURE (°C)

0

SCHOTTKY LEAKAGE CURRENT (µA)

3

6

9

12

15

3591 G11

VR = 10V
V

R

= 16V

V

R

= 20V

TEMPERATURE (°C)

–50 –25

40

OUTPUT CLAMP VOLTAGE (V)

42

45

0

50

75

3591 G12

41

44

43

25

100

125

TEMPERATURE (°C)

–50

INPUT CURRENT (mA)

25 75

3591 G13

–25 0

50 100 125

VIN = 3V

4

5

6

3

2

0

1

8

7

TEMPERATURE (°C)

–50

SWITCHING FREQUENCY (kHz)

25 75

3591 G14

–25 0

50 100 125

1000

1050

1100

950

900

750

800

850

1200

1150

TEMPERATURE (°C)

–50

MAXIMUM DUTY CYCLE (%)

25 75

3591 G15

–25 0

50 100 125

98

96

94

90

92

100

V

CAP

(V)

5

SENSE VOLTAGE (mV)

20 30

3591 G16

10 15

25 35

204

200

196

188

192

208

–50°C

125°C

25°C

TEMPERATURE (°C)

–50 –25

188

SENSE VOLTAGE (mV)

196

208

0

50

75

3591 G17

192

204

200

25

100

125

TYPICAL PERFORMANCE CHARACTERISTICS

Quiescent Current
(V

CTRL

= 3V) Current Limit vs Temperature

Schottky Leakage Current
vs Temperature

Open-Circuit Output Clamp
Voltage vs Temperature

Input Current in Output Open
Circuit vs Temperature

Switching Frequency
vs Temperature

Maximum Duty Cycle
vs Temperature

Sense Voltage (V

CAP

– V

LED

)

vs V

CAP

Sense Voltage (V

CAP

– V

LED

)

vs Temperature

T

A

= 25°C, unless otherwise specifi ed.

LT3591

5

3591f

BLOCK DIAGRAM

PIN FUNCTIONS

VIN (Pin 1): Input Supply Pin. Must be locally bypassed.

GND (Pin 2): Ground Pin. Should be tied directly to local

ground plane.

SW (Pin 4): Switch Pin. Minimize trace area at this pin to
minimize EMI. Connect the inductor at this pin.

CAP (Pin 5): Output of the Driver. This pin is connected
to the cathode of internal Schottky. Connect the output
capacitor to this pin and the sense resistor from this pin
to the LED pin.

LED (Pin 7): Connection Point for the Anode of the First
LED and the Sense Resistor. The LED current can be
programmed by :

I

mV

R

LED

SENSE

=

200

CTRL (Pin 8): Dimming and Shutdown Pin. Connect this
pin below 50mV to disable the driver. As the pin voltage
is ramped from 0V to 1.5V, the LED current ramps from
0 to I

LED

( = 200mV/R

SENSE

). The CTRL pin must not be

left fl oating.

Exposed Pad (Pin 9): Ground. The Exposed Pad must
be soldered to PCB ground to achieve the rated thermal
performance.

4

–

+

–

+

R

SW

CAP

1

V

IN

Q

S

DRIVER

Σ

OVERVOLTAGE

PROTECTION

RAMP

GENERATOR

OSCILLATOR

V

REF

1.25V

START-UP

CONTROL

SHDN

Q1

R

–

+

+

5

LED

3591 F01

CTRL GND

7

82

–

+

A = 6.25

A1

R

C

C

C

A2

A3

PWM

COMP

Figure 1. Block Diagram