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LT3756/LT3756-1

100V

IN

, 100V

OUT

LED Controller

FEATURES

n

DESCRIPTION

The LT

®

3756 and LT3756-1 are DC/DC controllers designed

to operate as a constant-current source for driving high

current LEDs. They drive a low side external N-channel

power MOSFET from an internal regulated 7V supply. The

ﬁxed frequency, current-mode architecture results in stable

operation over a wide range of supply and output voltages.

A ground referenced voltage FB pin serves as the input for

several LED protection features, and also makes it possible

for the converter to operate as a constant-voltage source.

A frequency adjust pin allows the user to program the

frequency from 100kHz to 1MHz to optimize efﬁciency,

performance or external component size.

The LT3756/LT3756-1 sense output current at the high

side of the LED string. High side current sensing is the

most ﬂexible scheme for driving LEDs, allowing boost,

buck mode or buck-boost mode conﬁguration. The PWM

input provides LED dimming ratios of up to 3000:1, and the

CTRL input provides additional analog dimming capability.

Both parts are available in the 16-lead QFN (3mm

×

3mm)

and MSOP packages.

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. Protected by U.S. Patents, including 7199560

and 7321203.

3000:1 True Color PWM

TM

Dimming

Wide Input Voltage Range: 6V to 100V

Output Voltage Up to 100V

Constant-Current and Constant-Voltage Regulation

100mV High Side Current Sense

Drives LEDs in Boost, Buck Mode, Buck-Boost Mode,

SEPIC or Flyback Topology

Adjustable Frequency: 100kHz to 1MHz

Open LED Protection

Programmable Undervoltage Lockout with Hysteresis

Open LED Status Pin (LT3756)

Frequency Synchronization (LT3756-1)

PWM Disconnect Switch Driver

CTRL Pin Provides Analog Dimming

Low Shutdown Current: <1μA

Programmable Soft-Start

Thermally Enhanced 16-Lead QFN (3mm

×

3mm)

and MSOP Packages

APPLICATIONS

n

High Power LED Applications

Industrial

Automotive

TYPICAL APPLICATION

V

IN

8V TO 60V

(100V TRANSIENT)

4.7μF

1M

V

REF

332k

CTRL

INTV

CC

100k

ISN

40.2k

GATE

OPENLED

PWM

SS

R

T

PWMOUT

V

C

GND INTV

CC

10k

0.001μF

3756 TA01a

94% Efﬁcient 30W White LED Headlamp Driver

22μH

V

IN

SHDN/UVLO

FB

ISP

LT3756

0.27Ω

370mA

14k

1M

4.7μF

Efﬁciency vs V

IN

100

96

EFFICIENCY (%)

30W

LED

STRING

332k

92

88

SENSE

0.018Ω

84

0.01μF

28.7k

400kHz

1%

80

10k

4.7μF

0

20

40

V

IN

(V)

60

80

37561 TA01b

37561f

1

LT3756/LT3756-1

ABSOLUTE MAXIMUM RATINGS

(Note 1)

V

IN

..........................................................................100V

SHDN/UVLO

.......................................... 100V, V

IN

+ 0.3V

ISP ISN ...................................................................100V

,

INTV

CC

...................................................... 8V, V

IN

+ 0.3V

GATE, PWMOUT ........................................INTV

CC

+ 0.3V

CTRL, PWM,

OPENLED

.............................................12V

VC, V

REF

, SS, FB .........................................................3V

SYNC ..........................................................................8V

RT ............................................................................1.5V

SENSE......................................................................0.5V

Operating Junction Temperature Range

(Note 2) ............................................. –40°C to 125°C

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

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

PIN CONFIGURATION

TOP VIEW

CTRL

ISN

12 FB

17

11 PWMOUT

10 GATE

9 SENSE

5

RT

6

SHDN/UVLO

7

INTV

CC

8

V

IN

ISP

VC

16 15 14 13

16

15

14

13

12

11

10

9

GATE

SENSE

V

IN

INTV

CC

SHDN/UVLO

RT

SS

SYNC OR

OPENLED

V

REF

1

PWM 2

SYNC OR

OPENLED

3

SS 4

TOP VIEW

PWMOUT

FB

ISN

ISP

VC

CTRL

V

REF

PWM

1

2

3

4

5

6

7

8

MSE PACKAGE

16-LEAD PLASTIC MSOP

T

JMAX

= 125°C,

θ

JA

= 43°C/W,

θ

JC

= 4°C/W

EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB

UD PACKAGE

16-LEAD (3mm 3mm) PLASTIC QFN

T

JMAX

= 125°C,

θ

JA

= 68°C/W,

θ

JC

= 4.2°C/W

EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB

ORDER INFORMATION

LEAD FREE FINISH

LT3756EMSE#PBF

LT3756IMSE#PBF

LT3756EMSE-1#PBF

LT3756IMSE-1#PBF

LT3756EUD#PBF

LT3756IUD#PBF

LT3756EUD-1#PBF

LT3756IUD-1#PBF

TAPE AND REEL

LT3756EMSE#TRPBF

LT3756IMSE#TRPBF

LT3756EMSE-1#TRPBF

LT3756IMSE-1#TRPBF

LT3756EUD#TRPBF

LT3756IUD#TRPBF

LT3756EUD-1#TRPBF

LT3756IUD-1#TRPBF

PART MARKING*

3756

37561

LDMQ

LDMR

PACKAGE DESCRIPTION

16-Lead Plastic MSOP

16-Lead (3mm

×

3mm) Plastic QFN

16-Lead (3mm

×

3mm) Plastic QFN

16-Lead (3mm

×

3mm) Plastic QFN

16-Lead (3mm

×

3mm) Plastic QFN

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/

This product is only offered in trays. For more information go to:

http://www.linear.com/packaging/

37561f

2

LT3756/LT3756-1

ELECTRICAL CHARACTERISTICS

PARAMETER

V

IN

Minimum Operating Voltage

V

IN

Shutdown I

Q

V

IN

Operating I

Q

(Not Switching)

V

REF

Voltage

V

REF

Line Regulation

SENSE Current Limit Threshold

SENSE Input Bias Current

SS Pull-Up Current

Error Ampliﬁer

LED Current Sense Threshold (V

ISP

– V

ISN

)

CTRL Threshold Linear Programming Range

CTRL Input Bias Current

LED Current Sense Ampliﬁer Input Common Mode

Range (V

ISP

)

ISP/ISN Short-Circuit Threshold (V

ISP

– V

ISN

)

ISP/ISN Short-Circuit Fault Sensing Common Mode

Range (V

ISN

)

ISP/ISN Input Bias Current

LED Current Sense Ampliﬁer g

m

VC Output Impedance

VC Standby Input Bias Current

FB Regulation Voltage (V

FB

)

V

ISP

= V

ISN

FB Ampliﬁer g

m

FB Pin Input Bias Current

FB Open LED Threshold

FB Overvoltage Threshold

VC Current Mode Gain –

ΔV

VC

/ΔV

SENSE

Oscillator

Switching Frequency

Minimum Off-Time

Linear Regulator

INTV

CC

Regulation Voltage

Dropout (V

IN

– INTV

CC

)

INTV

CC

Undervoltage Lockout

INTV

CC

Current Limit

INTV

CC

Current in Shutdown

SHDN/UVLO

= 0V, INTV

CC

= 7V

I

INTVCC

= –10mA, V

IN

= 7V

3.9

14

7

7.15

1

4.1

18

8

4.3

23

12

7.3

V

mA

μA

37561f

The

l

denotes the speciﬁcations which apply over the full operating temp-

erature range, otherwise speciﬁcations are at T

A

= 25°C. V

IN

= 24V,

SHDN/UVLO

= 24V, CTRL = 2V, PWM = 5V, unless otherwise noted.

CONDITIONS

V

IN

Tied to INTV

CC

SHDN/UVLO

= 0V, PWM = 0V

SHDN/UVLO

= 1.15V, PWM = 0V

VC = 0V, RT = 100k to GND

100μA ≤ I

VREF

≤ 0μA

6V ≤ V

IN

≤ 100V

98

Current Out of Pin

FB = 0V, V

ISP

= 48V

l

MIN

TYP

0.1

1.4

MAX

6

1

5

1.7

2.045

118

13

103

–8

1.1

100

UNITS

V

μA

mA

V

%/V

mV

μA

mV

V

nA

V

mV

V

μA

μS

kΩ

1.965

2.00

0.006

108

40

10.5

100

–10

50

8

96

–13

0

LED Current Sense Threshold at CTRL = 0V (V

ISP

– V

ISN

) CTRL = 0V, FB = 0V, V

ISP

= 48V

Current Out of Pin

2.9

V

ISN

= 0V

115

0

PWM = 5V (Active), V

ISP

= 48V

PWM = 0V (Standby), V

ISP

= 48V

V

ISP

– V

ISN

= 100mV

1V < V

VC

< 2V

PWM = 0V

l

150

200

3

50

0

120

15000

–20

1.220

1.232

1.250

480

40

V

FB

–

60mV

V

FB

+

50mV

V

FB

–

50mV

V

FB

+

60mV

4

0.1

20

1.270

1.265

100

V

FB

–

40mV

V

FB

+

70mV

nA

V

μS

nA

V

V/V

FB = V

FB

, V

ISP

= V

ISN

Current Out of Pin

OPENLED

Falling (LT3756 Only)

PWMOUT Falling

R

T

= 100k

R

T

= 10k

l

90

925

105

1000

170

125

1050

kHz

ns

3

LT3756/LT3756-1

ELECTRICAL CHARACTERISTICS

PARAMETER

Logic Inputs/Outputs

PWM Input High Voltage

PWM Input Low Voltage

PWM Pin Resistance to GND

PWMOUT Output Low (V

OL

)

PWMOUT Output High (V

OH

)

SHDN/UVLO

Threshold Voltage Falling

SHDN/UVLO

Rising Hysteresis

SHDN/UVLO

Input Low Voltage

SHDN/UVLO

Pin Bias Current Low

SHDN/UVLO

Pin Bias Current High

OPENLED

Output Low (V

OL

)

SYNC Pin Resistance to GND

SYNC Input High

SYNC Input Low

Gate Driver

t

r

GATE Driver Output Rise Time

t

f

GATE Driver Output Fall Time

GATE Output Low (V

OL

)

GATE Output High (V

OH

)

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.

INTV

CC

– 50mV

C

L

= 3300pF

C

L

= 3300pF

35

0.05

ns

V

I

VIN

Drops Below 1μA

SHDN/UVLO

= 1.15V

SHDN/UVLO

= 1.30V

I

OPENLED

= 0.5mA (LT3756 Only)

LT3756-1 Only

1.5

0.4

30

1.7

2.05

10

l

The

l

denotes the speciﬁcations which apply over the full operating temp-

erature range, otherwise speciﬁcations are at T

A

= 25°C. V

IN

= 24V,

SHDN/UVLO

= 24V, CTRL = 2V, PWM = 5V, unless otherwise noted.

CONDITIONS

MIN

1.5

0.4

45

INTV

CC

– 50mV

1.185

1.220

20

0.4

2.5

100

200

1.245

60

0

50

TYP

MAX

UNITS

V

kΩ

mV

V

mV

V

μA

nA

mV

kΩ

V

Note 2:

The LT3756E and LT3756E-1 are 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 LT3756I and LT3756I-1 are guaranteed to meet performance

speciﬁcations over the –40°C to 125°C operating junction temperature

range.

37561f

4

LT3756/LT3756-1

TYPICAL PERFORMANCE CHARACTERISTICS

V

ISP

– V

ISN

Threshold vs V

CTRL

120

100

V

ISP

- V

ISN

THRESHOLD (mV)

80

60

40

20

0

–20

0

0.5

1

V

CTRL

(V)

3756 G01

T

A

= 25°C, unless otherwise noted.

V

ISP

– V

ISN

Threshold

vs Temperature

103

102

101

100

99

98

97

–50

V

CTRL

= 2V

V

ISP

– V

ISN

Threshold vs V

ISP

103

102

101

100

99

98

97

V

CTRL

= 2V

V

ISP

- V

ISN

THRESHOLD (mV)

V

ISP

–V

ISN

THRESHOLD (mV)

1.5

2

0

20

40

60

ISP VOLTAGE (V)

80

100

3756 G02

–25

50

25

0

75

TEMPERATURE (°C)

100

125

37561 G03

FB Voltage vs Temperature

1.28

1.27

1.26

1.25

V

REF

(V)

V

FB

(V)

1.24

1.23

1.22

1.21

1.20

–50

2.04

2.03

2.02

2.01

2.00

1.99

1.98

1.97

50

25

0

75

TEMPERATURE (°C)

125

V

REF

Voltage vs Temperature

2.04

2.03

2.02

2.01

V

REF

(V)

2.00

1.99

1.98

1.97

1.96

–25

50

25

0

75

TEMPERATURE (°C)

100

125

V

REF

Voltage vs V

IN

–25

100

1.96

–50

0

20

40

60

V

IN

(V)

80

100

37561 G06

37561 G04

37561 G05

Switching Frequency vs R

T

10000

1400

1300

SWITCHING FREQUENCY (kHz)

1200

1100

1000

900

800

700

10

Switching Frequency

vs Temperature

R

T

= 10k

2.4

SHDN/UVLO

Hysteresis Current

vs Temperature

2.2

I

SHDN/UVLO

(μA)

125

1000

2.0

100

1.8

10

R

T

(k)

100

37561 G07

600

–50

–25

50

25

0

75

TEMPERATURE (°C)

100

1.6

–50

–25

50

25

0

75

TEMPERATURE (°C)

100

125

37561 G08

37561 G09

37561f

5

LT3756IMSE-1-PBF

LT3756IMSE-1-PBF概述

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