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FEATURES

n

LT3592

500mA Wide Input Voltage

Range Step-Down LED Driver

with 10:1 Dimming

DESCRIPTION

The LT

®

3592 is a ﬁxed frequency step-down DC/DC con-

verter designed to operate as a constant-current source.

An external sense resistor monitors the output current

allowing accurate current regulation, ideal for driving

high current LEDs. The output current can be dimmed

by a factor of 10 using an external signal for nighttime

brake lights.

The high switching frequency offers several advantages by

permitting the use of a small inductor and small ceramic

capacitors. Small components combined with the LT3592’s

10-pin DFN leadless surface mount package save space and

cost versus alternative solutions. The constant switching

frequency combined with low-impedance ceramic capaci-

tors result in low, predictable output ripple.

A wide input voltage range of 3.6V to 36V makes the

LT3592 useful in a variety of applications. Current mode

PWM architecture provides fast transient response and

cycle-by-cycle current limiting. Thermal shutdown provides

additional protection.

L,

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

All other trademarks are the property of their respective owners.

Wide Input Voltage Range

Operation from 3.6V to 36V

Resistor Adjustable 400kHz–2.2MHz Switching

Frequency

Shorted and Open LED Protected

Internal Switch Current Sense Resistor

External Resistor Programs LED Current, Pin

Selects 10:1 Ratio

50mA/500mA LED Current Settings

Catch Diode Current Sense to Prevent Runaway at

High V

IN

Small Thermally Enhanced 10-Lead DFN

(2mm

×

3mm) and MSOP-10 Packages

APPLICATIONS

n

Automotive Signal Lighting

Industrial Lighting

Constant-Current, Constant Voltage Supplies

TYPICAL APPLICATION

50/500mA Two Series Red LED Driver

V

IN

7V TO 32V

V

IN

1μF

BOOST

LT3592

SW

EFFICIENCY (%)

DA

CAP

OUT

V

FB

10k

0.1μF 10μH

Efﬁciency for 2 Red LEDs, L = 10μH, 900kHz

100

95

90

85

80

75

70

65

BRIGHT 500mA

ON

BRAKE

SHDN

BRIGHT

R

T

+

200/20mV

–

51k

0.4Ω

4.7μF

60

55

50

3592 TA01a

140k

900kHz

GND

4

8

16

12

20

INPUT VOLTAGE (V)

24

28

3592 TA01b

3592fa

1

LT3592

ABSOLUTE MAXIMUM RATINGS

(Note 1)

V

IN

, BRIGHT Voltages ................................ –0.3V to 36V

BOOST Voltage .........................................................60V

BOOST above SW pin ...............................................30V

CAP OUT Voltages (OUT ≤ CAP) ...............................30V

,

V

FB

Voltage .................................................................4V

R

T

Voltage ...................................................................6V

SHDN

Voltage ............................................................V

IN

DA Pin Current (Average)..................... –1.2A (sourcing)

Operating Temperature Range (Notes 2, 3)

LT3592E ............................................. –40°C to 125°C

LT3592I .............................................. –40°C to 125°C

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

PIN CONFIGURATION

TOP VIEW

R

T

BRIGHT

SHDN

V

IN

DA

1

2

3

4

5

11

10 V

FB

9 OUT

8 CAP

7 BOOST

6 SW

R

T

BRIGHT

SHDN

V

IN

DA

1

2

3

4

5

10

9

8

7

6

V

FB

OUT

CAP

BOOST

SW

11

DDB PACKAGE

10-LEAD (3mm 2mm) PLASTIC DFN

θ

JA

= 76°C/W,

θ

JC

= 13.5°C/W

EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB

MSE PACKAGE

10-LEAD PLASTIC MSOP

θ

JA

= 38°C/W,

θ

JC

= 8°C/W

EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB

ORDER INFORMATION

LEAD FREE FINISH

LT3592EDDB#PBF

LT3592IDDB#PBF

LT3592EMSE#PBF

LT3592IMSE#PBF

LEAD BASED FINISH

LT3592EDDB

LT3592IDDB

LT3592EMSE

LT3592IMSE

TAPE AND REEL

LT3592EDDB#TRPBF

LT3592IDDB#TRPBF

LT3592EMSE#TRPBF

LT3592IMSE#TRPBF

TAPE AND REEL

LT3592EDDB#TR

LT3592IDDB#TR

LT3592EMSE#TR

LT3592IMSE#TR

PART MARKING*

LDCQ

LTDCR

PART MARKING

LDCQ

LTDCR

PACKAGE DESCRIPTION

10-Lead (3mm

×

2mm) Plastic DFN

10-Lead (3mm

×

2mm) Plastic DFN

10-Lead Plastic MSOP

PACKAGE DESCRIPTION

10-Lead (3mm

×

2mm) Plastic DFN

10-Lead (3mm

×

2mm) Plastic DFN

10-Lead Plastic MSOP

TEMPERATURE RANGE

–40°C to 125°C

TEMPERATURE RANGE

–40°C to 125°C

Consult LTC Marketing for parts speciﬁed with wider operating temperature ranges. *The temperature grade is identiﬁed by a label on the shipping container.

For more information on lead free part marking, go to:

http://www.linear.com/leadfree/

For more information on tape and reel speciﬁcations, go to:

http://www.linear.com/tapeandreel/

3592fa

2

LT3592

ELECTRICAL CHARACTERISTICS

PARAMETER

Minimum Input Voltage

Input Quiescent Current

- in Shutdown

CAP to OUT Voltage

Not Switching

V

SHDN

= 0.3V

0.4Ω CAP to OUT

BRIGHT = 1.4V

BRIGHT = 0.3V

R

T

= 357k

R

T

= 140k

R

T

= 48.7k

R

T

= 140k

l

The

l

denotes the speciﬁcations which apply over the full operating

temperature range, otherwise speciﬁcations are at T

A

= 25°C. V

IN

= 12V, V

BOOST

= 16V, V

OUT

= 4V unless otherwise noted. (Note 2)

CONDITIONS

l

MIN

TYP

3.25

2

0.1

MAX

3.6

3

2

210

22

–1.2

450

1000

2.5

UNITS

V

mA

μA

mV

A

kHz

MHz

%

V

190

18

–0.8

350

800

1.9

90

2.3

200

20

–1

400

900

2.2

94

DA Pin Current to Stop OSC

Switching Frequency

Maximum Duty Cycle

SHDN

Input High Voltage

SHDN

Input Low Voltage

BRIGHT Input High Voltage

BRIGHT Input Low Voltage

Switch Current Limit (Note 4)

Switch V

CESAT

Boost Pin Current

Switch Leakage Current

Minimum Boost Voltage

Boost Diode Forward Voltage

V

FB

Voltage

0.3

1.4

0.3

l

V

A

mV

mA

μA

V

mV

V

0.85

1.25

300

20

1

1.8

800

1.5

30

10

2.5

1.235

I

SW

= 500mA

I

SW

= 500mA

V

OUT

= 4V

I

DIO

= 50mA

OUT = CAP = 4V

l

1.185

1.21

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.

Note 2:

The LT3592E is guaranteed to meet performance speciﬁcations

from 0°C to 125°C junction temperature. Speciﬁcations over the –40°C

to 125°C operating junction temperature range are assured by design,

characterization and correlation with statistical process controls. The

LT3592I is guaranteed over the full –40°C to 125°C operating junction

temperature range. The operating lifetime is derated at junction

temperatures greater than 125°C.

Note 3:

This IC includes overtemperature protection that is intended

to protect the device during momentary overload conditions. Junction

temperature will exceed the maximum operating junction temperature

when overtemperature protection is active. Continuous operation above

the speciﬁed maximum operating junction temperature may result in

device degradation or failure.

Note 4:

Switch Current Measurements are performed when the outputs

are not switching. Slope compensation reduces current limit at higher duty

cycles.

3592fa

3

LT3592

TYPICAL PERFORMANCE CHARACTERISTICS

Efﬁciency (2 Red LEDS,

L = 10μH, 900kHz)

100

95

90

85

EFFICIENCY (%)

80

75

70

65

60

55

50

45

40

4

8

16

12

20

INPUT VOLTAGE (V)

24

28

3592 G01

(T

A

= 25°C, unless otherwise noted)

Efﬁciency (2 Red LEDs,

L = 22μH, 400kHz)

100

95

90

EFFICIENCY (%)

BRIGHT (500mA)

Efﬁciency (1 Red LED,

L = 6.8μH, 900kHz)

100

95

90

BRIGHT (500mA)

EFFICIENCY (%)

85

80

75

70

65

60

55

50

45

40

4

8

16

12

20

INPUT VOLTAGE (V)

24

28

3592 G02

BRIGHT (500mA)

85

80

75

70

65

60

55

50

4

8

16

20

12

INPUT VOLTAGE (V)

24

28

3592 G03

Efﬁciency (2 Red LEDs,

L = 4.7μH, 2.2MHz)

100

95

90

EFFICIENCY (%)

85

80

75

70

65

60

55

50

4

8

16

12

20

INPUT VOLTAGE (V)

24

28

3592 G04

Minimum V

IN

for 500mA Output

Current vs V

OUT

, L = 22μH,

f = 400kHz (LED Loads)

12

11

10

OUTPUT VOLTAGE (V)

12

11

10

OUTPUT VOLTAGE (V)

9

8

7

6

5

4

3

2

4

6

8

INPUT VOLTAGE (V)

10

12

3592 G05

Minimum V

IN

for 500mA Output

Current vs V

OUT

, L = 6.8μH,

f = 900kHz (LED Loads)

BRIGHT (500mA)

9

8

7

6

5

4

3

2

4

6

8

INPUT VOLTAGE (V)

10

12

3592 G06

Minimum V

IN

for 500mA Output

Current vs V

OUT

, L = 22μH,

f = 400kHz (LED Loads)

12

11

10

OUTPUT VOLTAGE (V)

V

IN

– V

SW

(mV)

9

8

7

6

5

4

3

2

4

6

10

12

8

INPUT VOLTAGE (V)

14

16

3592 G07

Switch Voltage Drop

vs Switch Current

500

450

400

350

300

250

200

150

100

50

0

100 200 300 400 500 600 700 800

SWITCH CURRENT (mA)

3592 G08

Switch Voltage Drop at 500mA

vs Temperature

400

375

350

325

300

275

250

–50

V

IN

– V

SW

(mV)

0

100

50

TEMPERATURE (°C)

150

3592 G09

3592fa

4

LT3592

TYPICAL PERFORMANCE CHARACTERISTICS

Undervoltage Lockout

vs Temperature

3.4

2300

2100

UNDERVOLTAGE LOCKOUT (V)

1900

3.3

f

SW

(kHz)

1700

1500

1300

1100

900

700

500

3.1

–50

0

50

100

TEMPERATURE (°C)

150

3592 G10

(T

A

= 25°C, unless otherwise noted)

Switching Frequency

vs Temperature

1400

R

T

= 48.7k

SWITCH CURRENT LIMIT (mA)

1200

1000

800

600

400

200

Current Limit During Soft Start

3.2

R

T

= 140k

R

T

= 357k

300

–50 –30 –10 10 30 50 70 90 110 130

TEMPERATURE (°C)

3592 G11

0

0.5

1

1.5

V

SHDN

(V)

2

2.5

3592 G12

Frequency Foldback

2500

R

T

= 48.7k

SWITCH CURRENT LIMIT (A)

1.4

1.3

1.2

1.1

1

0.9

0.8

0.7

0.6

0

600 800 1000 1200 1400 1600 1800 2000 2200

SHDN

VOLTAGE (mV)

3592 G13

Switch Current Limit

1.50

1.45

SWITCH CURRENT LIMIT (A)

1.40

1.35

1.30

1.25

1.20

1.15

1.10

1.05

0

20

40

60

DUTY CYCLE (%)

80

100

3592 G14

Switch Current Limit

2000

FREQUENCY (kHz)

1500

TYPICAL

1000

500

0.5

1.00

–50 –30 –10 10 30 50 70 90 110 130

TEMPERATURE (°C)

3592 G15

Operating Waveforms

Operating Waveforms,

Discontinuous Mode

V

SW

5V/DIV

V

CAP

10mV/DIV

AC COUPLED

I

L

500mA/DIV

500ns/DIV

3592 G16

V

SW

5V/DIV

V

CAP

10mV/DIV

AC COUPLED

I

L

500mA/DIV

500ns/DIV

3592 G17

3592fa

5

LT3592IDDB-PBF

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