CDRH3D18-220NC_技术文档

LT3591

White LED Driver with

Integrated Schottky in

3mm × 2mm DFN

FEATURES

DESCRIPTION

TheLT^®3591isaﬁxedfrequencystep-upDC/DCconverter

speciﬁcallydesignedtodriveuptotenwhiteLEDsinseries

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

featuresauniquehighsideLEDcurrentsensethatenables

the part to function as a “one wire current source;” one

sideoftheLEDstringcanbereturnedtogroundanywhere,

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.

■

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 PWM^TMDimming Range

■

42V Open LED Protection

■

1MHz Switching Frequency

■

5ꢀ Reference Accuracy

■

V Range: 2.5V to 12V

IN

■

Requires Only 2.2µF Output Capacitor

■

Low Proﬁle 8-Lead DFN Package

(3mm × 2mm × 0.75mm)

The high switching frequency allows the use of tiny induc-

tors and capacitors. A single pin performs both shutdown

and accurate LED dimming control. Few external compo-

nents are needed: open-LED protection and the Schottky

diode are all contained inside a low proﬁle 3mm × 2mm

DFN package.

APPLICATIONS

■

Cellular Phones

■

PDAs, Handheld Computers

■

Digital Cameras

, 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.

■

MP3 Players

■

GPS Receivers

TYPICAL APPLICATION

Li-Ion Driver for Ten White LEDs

Conversion Efﬁciency

80

SHUTDOWN AND

DIMMING CONTROL

V

= 3.6V

IN

10 LEDs

75

70

65

60

55

CTRL

V

IN

V

CAP

LED

IN

3V TO 5V

R

SENSE

LT3591

GND

22µH

1µF

10Ω

SW

2.2µF

0

5

10

15

20

LED CURRENT (mA)

3591 TA01b

3591 TA01a

3591f

1

LT3591

ABSOLUTE MAXIMUM RATINGS

PACKAGE/ORDER INFORMATION

(Note 1)

TOP VIEW

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

IN

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

V

1

2

3

4

8

7

6

5

CTRL

LED

NC

IN

GND

NC

9

SW

CAP

DDB PACKAGE

8-LEAD (3mm × 2mm) PLASTIC DFN

= 125°C, θ = 76°C/W

T

JMAX

JA

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

ORDER PART NUMBER

DDB PART MARKING

LCPG

LT3591EDDB

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.

ELECTRICAL CHARACTERISTICS ^The

●

denotes the speciﬁcations which apply over the full operating

temperature range, otherwise speciﬁcations are at T = 25°C. V = 3V, V = 3V, unless otherwise speciﬁed.

CTRL

A

IN

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

V

Minimum Operating Voltage

LED Current Sense Voltage (V

CAP Pin Bias Current

LED Pin Bias Current

Supply Current

2.5

●

– V

)

LED

V

= 24V, I = 300mA

190

200

40

210

80

mV

µA

CAP

SW

V

= 36V, V

= 24V, V

= 35.8V

= 23V

LED

20

40

µA

4

9

5

11

mA

µA

CTRL = 0V

Switching Frequency

Maximum Duty Cycle

Switch Current Limit

0.75

92

1

1.2

MHz

ꢀ

94

●

500

800

200

0.1

mA

mV

µA

V

Switch V

I

= 300mA

= 24V

CESAT

SW

Switch Leakage Current

V

5

SW

●

V

CTRL

V

CTRL

V

CTRL

for Full LED Current

to Shut Down IC

to Turn On IC

= 44V

1.5

CAP

50

mV

nA

V

●

100

CTRL Pin Bias Current

100

42

●

CAP Pin Overvoltage Protection

Schottky Forward Drop

40

44

4

I

= 200mA

0.8

V

SCHOTTKY

Schottky Leakage Current

V = 30V

µA

R

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 LT3591E is guaranteed to meet performance speciﬁcations

from 0°C to 85°C operating junction temperature range. Speciﬁcations

over the –40°C to 85°C operating junction temperature range are assured

by design, characterization and correlation with statistical process controls.

3591f

2

LT3591

TYPICAL PERFORMANCE CHARACTERISTICS

T = 25°C, unless otherwise speciﬁed.

A

Switch Saturation Voltage

CESAT

(V

)

Schottky Forward Voltage Drop

Shutdown Current (V

= 0V)

CTRL

15

12

9

600

500

400

300

200

100

0

500

400

300

200

100

0

25°C

125°C

–50°C

125°C

25°C

6

–50°C

3

0

6

9

0

12

3

0

200

400

600

800 1000 1200

400

700 800

0

100 200 300

500 600

V

(V)

IN

SCHOTTKY FORWARD DROP (mV)

SWITCH CURRENT (mA)

3591 G03

3591 G02

3591 G01

Sense Voltage (V

– V

)

LED

Open-Circuit Output

Clamp Voltage

Input Current in Output

Open Circuit

CAP

vs V

CTRL

240

200

160

120

80

8

7

6

5

4

3

2

1

0

45

44

43

42

41

40

–50°C

25°C

125°C

25°C

125°C

–50°C

25°C

125°C

–50°C

40

0

3

6

9

12

0

500 1000 1500 2000 2500 3000

(mV)

6

0

3

9

12

V

(V)

V

(V)

IN

CTRL

IN

3591 G06

3591 G04

3591 G05

Switching Waveform

Transient Response

V

CAP

V

SW

5V/DIV

20V/DIV

V

CAP

CTRL

50mV/DIV

5V/DIV

I

L

I

L

200mA/DIV

500mA/DIV

3591 G07

3591 G08

V

= 3.6V

500ms/DIV

V

= 3.6V

IN

1ms/DIV

IN

FRONT PAGE

APPLICATION CIRCUIT

FRONT PAGE

APPLICATION CIRCUIT

3591f

3

LT3591

TYPICAL PERFORMANCE CHARACTERISTICS ^{T = 25°C, unless otherwise speciﬁed.}

A

Quiescent Current

CTRL

Schottky Leakage Current

vs Temperature

(V

= 3V)

Current Limit vs Temperature

15

12

9

6

5

1000

800

600

400

200

0

V

= 10V

= 16V

= 20V

R

25°C

125°C

–50°C

4

3

6

2

1

0

3

0

50

100 125

–50 –25

0

25

75

0

3

6

9

12

–50 –25

0

25

50

75 100 125

TEMPERATURE (°C)

V

(V)

TEMPERATURE (°C)

IN

3591 G11

3591 G09

3591 G10

Open-Circuit Output Clamp

Voltage vs Temperature

Input Current in Output Open

Circuit vs Temperature

Switching Frequency

vs Temperature

45

44

43

42

41

40

1200

1150

1100

1050

1000

950

8

V

IN

= 3V

7

6

5

4

3

2

1

0

900

850

800

750

–50 –25

0

25

50

75 100 125

50

TEMPERATURE (°C)

100 125

–50 –25

0

25

75

50

TEMPERATURE (°C)

100 125

–50 –25

0

25

75

TEMPERATURE (°C)

3591 G12

3591 G14

3591 G13

Maximum Duty Cycle

vs Temperature

Sense Voltage (V

– V

)

Sense Voltage (V

vs Temperature

– V

)

LED

CAP

LED

CAP

vs V

CAP

208

204

200

196

192

188

100

98

96

94

92

90

208

204

200

196

192

188

25°C

125°C

–50°C

50

TEMPERATURE (°C)

100 125

–50 –25

0

25

75

–50 –25

0

25

50

75 100 125

25

35

5

10

15

20

30

TEMPERATURE (°C)

V

(V)

CAP

3591 G15

3591 G17

3591 G16

3591f

4

LT3591

PIN FUNCTIONS

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

IN

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

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

ground plane.

0 to I

( = 200mV/R

). The CTRL pin must not be

LED

SENSE

SW (Pin 4): Switch Pin. Minimize trace area at this pin to

minimize EMI. Connect the inductor at this pin.

left ﬂoating.

Exposed Pad (Pin 9): Ground. The Exposed Pad must

be soldered to PCB ground to achieve the rated thermal

performance.

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 :

200mV

R_SENSE

I_LED

=

BLOCK DIAGRAM

1

4

SW

V

IN

PWM

COMP

CAP

5

–

+

DRIVER

A2

Q1

R

Q

S

OVERVOLTAGE

PROTECTION

+

–

R

A3

Σ

RAMP

GENERATOR

V

REF

+

–

OSCILLATOR

SHDN

1.25V

–

+

A = 6.25

LED

A1

7

R

C

START-UP

CONTROL

CTRL GND

2

8

3591 F01

Figure 1. Block Diagram

3591f

5

LT3591

OPERATION

The LT3591 uses a constant frequency, current mode

control scheme to provide excellent line and load regula-

tion. Operation can be best understood by referring to the

Block Diagram in Figure 1.

the LED current. The LT3591 enters into shutdown when

CTRL is pulled lower than 50mV.

Minimum Output Current

The LT3591 can drive a 2-LED string at 2mA LED current

without pulse skipping using the same external compo-

nents shown in the application circuit on the front page of

this data sheet. As current is further reduced, the device

will begin skipping pulses. This will result in some low

frequencyripple,althoughtheaverageLEDcurrentremains

regulateddowntozero.ThephotoinFigure2detailscircuit

operationdrivingtwowhiteLEDsat2mAload.Peakinduc-

tor current is less than 40mA and the regulator operates

in discontinuous mode, meaning the inductor current

reacheszeroduringthedischargephase.Aftertheinductor

current reaches zero, the SW pin exhibits ringing due to

the LC tank circuit formed by the inductor in combination

with the switch and the diode capacitance. This ringing is

not harmful; far less spectral energy is contained in the

ringing than in the switch transitions.

At power-up, the capacitor at the CAP pin is charged up

to V (input supply voltage) through the inductor and

IN

the internal Schottky diode. If CTRL is pulled higher than

100mV, the bandgap reference, the start-up bias and the

oscillatorareturnedon.Atthestartofeachoscillatorcycle,

the power switch Q1 is turned on. A voltage proportional

to the switch current is added to a stabilizing ramp and the

resulting sum is fed into the positive terminal of the PWM

comparator, A2. When this voltage exceeds the level at the

negative input of A2, the PWM logic turns off the power

switch. The level at the negative input of A2 is set by the

error ampliﬁer A1, and is simply an ampliﬁed version of

the difference between the V

and V voltage and the

CAP

LED

bandgap reference. In this manner the error ampliﬁer, A1,

sets the correct peak current level in inductor L1 to keep

the output in regulation. The CTRL pin is used to adjust

I

L

20mA/DIV

V

SW

5V/DIV

3591 F02

V

= 4.2V

500ns/DIV

IN

I

= 2mA

LED

2 LEDs

Figure 2. Switching Waveforms

3591f

6

LT3591

APPLICATIONS INFORMATION

INDUCTOR SELECTION

CAPACITOR SELECTION

A 22µH inductor is recommended for most LT3591 ap-

plications. Although small size and high efﬁciency are

major concerns, the inductor should have low core losses

at 1MHz and low DCR (copper wire resistance). Some

small inductors in this category are listed in Table 1. The

efﬁciency comparison of different inductors is shown in

Figure 3.

The small size of ceramic capacitors make them ideal for

LT3591applications.UseonlyX5RandX7Rtypesbecause

they retain their capacitance over wider temperature

ranges than other types such as Y5V or Z5U. A 1µF input

capacitor and a 50V, 2.2µF output capacitor are sufﬁcient

for most applications.

A limited number of manufacturers produce small 50V

capacitors. Table 2 shows a list of several recommended

50V capacitors. Consult the manufacturer for detailed

information on their entire selection of ceramic parts.

Table 2. Recommended Output Capacitors

VOLTAGE CASE SIZE

Table 1. Recommended Inductors

MAX

CURRENT DIMENSION

L

(µH)

RATING

(mA)

L × W × H

PART

(mm)

VENDOR

VLF4012AT-

220MR51

22

510

490

560

420

TDK

4 ×3.8 ×1.2

4.1 ×4.1 ×1.8

4.1 ×4.1 ×2

4.8 ×3.4 ×2.8

www.tdk.com

C

HEIGHT

(mm)

VLCF4018T-

220MR49-2

PART

(µF) TEMP.

VENDOR

GRM21BR71H105KA12L

1

50V

X7R

50V

X7R

50V

X7R

50V

X7R

50V

X7R

0805

1.25 0.15

1206

Murata

VLCF4020T-

220MR56

www.murata.com

GRM31MR71H105KA88

1

LQH43CN220K03 22

Murata

www.murata.com

1.15 0.1

1206

NR4018T220M

NR4012T220M

22

590

510

600

Taiyo Yuden

4.2 ×4.2 ×1.8

4.2 ×4.2 ×1.2

4 × 4 ×2

GRM31CR71H225KA88 2.2

GRM31CR71H475KA12L 4.7

www.t-yuden.com

1.6 0.2

1206

CDRH3D18-

220NC

Sumida

www.sumida.com

1.6 0.2

1206

B82470-A1223-M 22

480

Epcos

www.epcos.com

4.8 ×4.8 ×1.2

UMK316BJ475KL-T

4.7

Taiyo Yuden

www.t-yuden.com

1.6 0.2

85

V

= 3.6V

IN

10 LEDs

80

75

70

65

60

55

50

TAIYO YUDEN NR4018T220M

TDK VLCF4018T-220MR49-2

TAIYO YUDEN NR4012T220M

TDKVLCF4012AT-220MR51

MURATA LQH43CN220K03

TDK VLCF4020T-220MR56

SUMIDA CDRH3D18-220NC

EPCOS B82470-A1223-M

0

5

10

LED CURRENT (mA)

15

20

3591 F03

Figure 3. Efﬁciency Comparison of Different Inductors

3591f

7

LT3591

APPLICATIONS INFORMATION

SCHOTTKY DIODE

For low DCR inductors, which is usually the case for this

application, the peak inrush current can be simpliﬁed as

follows:

The LT3591 has a built-in Schottky diode. The internal

schottky saves board space in space constrained appli-

cations. In less space sensitive applications, an external

schottky diode connected between the SW node and the

CAP node increases efﬁciency one to two percent. It is

important to use a properly rated schottky diode that can

handle the peak switch current of the LT3591. In addition,

theschottkydiodemusthaveabreakdownvoltageofatleast

40V along with a low forward voltage in order to achieve

higher efﬁciency. One recommended external schottky

diode for the LT3591 is the Phillips PMEG4005AEA.

V – 0.6

L • ω

α π

ω 2

⎛

⎞

IN

I_PK

=

• exp –

•

⎜

⎟

⎠

⎝

r

α =

ω =

2 •L

1

r²

4 •L²

–

L •C

where L is the inductance, r is the DCR of the inductor

and C is the output capacitance.

OVERVOLTAGE PROTECTION

Table 3 gives inrush peak currents for some component

selections.

Table 3. Inrush Peak Currents

The LT3591 has an internal open-circuit protection circuit.

In the cases of output open circuit, when the LEDs are

disconnected from the circuit or the LEDs fail open circuit,

V

(V)

r (Ω)

0.3

L (µH)

22

C

(µF)

I (A)

IN

OUT

P

V

is clamped at 42V (typ). The LT3591 will then switch

CAP

4.2

2.2

1.06

0.96

0.83

0.68

ataverylowfrequencytominimizeinputcurrent.TheV

CAP

4.2

0.71

0.58

1.6

22

2.2

1

and input current during output open circuit are shown in

the Typical Performance Characteristics. Figure 4 shows

the transient response when the LEDs are disconnected.

15

1

PROGRAMMING LED CURRENT

The feedback resistor (R ) and the sense voltage

I

L

500mA/DIV

SENSE

(V

– V ) control the LED current.

CAP

LED

V

CAP

20V/DIV

The CTRL pin controls the sense reference voltage as

shown in the Typical Performance Characteristics. For

CTRL higher than 1.5V, the sense reference is 200mV,

which results in full LED current. In order to have accurate

LED current, precision resistors are preferred (1ꢀ is rec-

3591 F04

V

= 3.6V

500µs/DIV

IN

CIRCUIT OF

FRONT PAGE LEDs DISCONNECTED

APPLICATION AT THIS INSTANT

ommended). The formula and table for R

are shown below.

selection

SENSE

Figure 4. Output Open-Circuit Waveform

200mV

I_LED

INRUSH CURRENT

R_SENSE

=

The LT3591 has a built-in Schottky diode. When supply

voltage is applied to the V pin, an inrush current ﬂows

IN

through the inductor and the Schottky diode and charges

up the CAP voltage. The Schottky diode inside the LT3591

can sustain a maximum current of 1A.

3591f

8

LT3591

APPLICATIONS INFORMATION

Table 4. R

Value Selection for 200mV Sense

The corner frequency of R1, C1 should be much lower

than the frequency of the PWM signal. R1 needs to be

much smaller than the internal impedance of the CTRL

pin which is 10MΩ (typ).

SENSE

I

(mA)

R

(Ω)

SENSE

LED

5

40

10

15

20

13.3

10

Direct PWM Dimming

Changing the forward current ﬂowing in the LEDs not only

changestheintensityoftheLEDs,italsochangesthecolor.

The chromaticity of the LEDs changes with the change in

forward current. Many applications cannot tolerate any

shift in the color of the LEDs. Controlling the intensity of

the LEDs with a direct PWM signal allows dimming of the

LEDs without changing the color. In addition, direct PWM

dimming offers a wider dimming range to the user.

DIMMING CONTROL

Therearethreedifferenttypesofdimmingcontrolcircuits.

The LED current can be set by modulating the CTRL pin

with a DC voltage, a ﬁltered PWM signal or directly with

a PWM signal.

Using a DC Voltage

Dimming the LEDs via a PWM signal essentially involves

turning the LEDs on and off at the PWM frequency. The

typical human eye has a limit of ~60 frames per second.

By increasing the PWM frequency to ~80Hz or higher,

the eye will interpret that the pulsed light source is con-

tinuously on. Additionally, by modulating the duty cycle

(amount of “on-time”), the intensity of the LEDs can be

controlled. The color of the LEDs remains unchanged in

this scheme since the LED current value is either zero or

a constant value.

Forsomeapplications,thepreferredmethodofbrightness

control is a variable DC voltage to adjust the LED current.

The CTRL pin voltage can be modulated to set the dim-

ming of the LED string. As the voltage on the CTRL pin

increases from 0V to 1.5V, the LED current increases from

0 to I . As the CTRL pin voltage increases beyond 1.5V,

LED

it has no effect on the LED current.

The LED current can be set by:

200mV

I_LED

≈

, when V_CTRL> 1.5V

R_SENSE

V_CTRL

6.25 •R_SENSE

Figure6showsaLi-IonpowereddriverfortenwhiteLEDs.

Direct PWM dimming method requires an external NMOS

tied between the cathode of the lowest LED in the string

I_LED

≈

, when V_CTRL< 1.25V

V

IN

3V TO

5V

Feedback voltage variation versus control voltage is given

in the Typical Performance Characteristics.

L1

22µH

V

IN

CAP

LED

SW

R

C1

1µF

LT3591

SENSE

10Ω

Using a Filtered PWM Signal

GND

C2

2.2µF

A ﬁltered PWM signal can be used to control the

brightness of the LED string. The PWM signal is ﬁltered

(Figure 5) by a RC network and fed to the CTRL pin.

CTRL

PWM

FREQ

5V

0V

Q1

Si2308

LT3591

CTRL

R1

100k

PWM

10kHz TYP

100k

C1

0.1µF

3591 F05

Figure 5. Dimming Control Using a Filtered PWM Signal

Figure 6. Li-Ion to Ten White LEDs with Direct PWM Dimming

3591f

9

LT3591

APPLICATIONS INFORMATION

and ground as shown in Figure 6. A Si2308 MOSFET can

beusedsinceitssourceisconnectedtoground. ThePWM

signalisappliedtotheCTRLpinoftheLT3591andthegate

of the MOSFET. The PWM signal should traverse between

0V to 5V, to ensure proper turn on and off of the driver

and the NMOS transistor Q1. When the PWM signal goes

high, the LEDs are connected to ground and a current of

Thecalculationsshowthatfora100Hzsignalthedimming

rangeis83to1. Inaddition, theminimumPWMdutycycle

of 1.2ꢀ ensures that the LED current has enough time

to settle to its ﬁnal value. Figure 8 shows the dimming

range achievable for different frequencies with a settling

time of 120µs.

10000

I

= 200mV/R

ﬂows through the LEDs. When the

LED

SENSE

PWM signal goes low, the LEDs are disconnected and

turn off. The MOSFET ensures that the LEDs quickly turn

off without discharging the output capacitor which in turn

allows the LEDs to turn on faster. Figure 7 shows the PWM

dimming waveforms for the circuit in Figure 6.

1000

PULSING MAY BE VISIBLE

100

10

PWM

5V/DIV

I

L

1

500mA/DIV

10

100

1000

10000

PWM DIMMING FREQUENCY (Hz)

3591 F08

I

LED

20mA/DIV

Figure 8. Dimming Range vs Frequency

3591 F07

V

= 3.6V

2ms/DIV

IN

10 LEDs

Inadditiontoextendingthedimmingrange,PWMdimming

improves the efﬁciency of the converter for LED currents

below 20mA. Figure 9 shows the efﬁciency for traditional

analog dimming of the front page application and PWM

dimming of the application in Figure 6.

Figure 7. Direct PWM Dimming Waveforms

The time it takes for the LED current to reach its pro-

grammed value sets the achievable dimming range for a

given PWM frequency. For example, the settling time of

the LED current in Figure 7 is approximately 120µs for a

3.6V input voltage. The achievable dimming range for this

application and 100Hz PWM frequency can be determined

using the following method.

80

PWM DIMMING

75

70

Example:

ƒ =100Hz, t_SETTLE=120µs

65

ANALOG DIMMING

1

60

t_PERIOD

=

= 0.01s

V

= 3.6V

ƒ 100

IN

10 LEDs

55

10

0

5

15

20

t_PERIOD

t_SETTLE120µs

0.01s

Dim Range=

=

= 83:1

LED CURRENT (mA)

3591 F09

Figure 9. PWM vs Analog Dimming Efﬁciency

t_SETTLE

t_PERIOD

120µs

0.01s

Min Duty Cycle =

•100=

•100=1.2%

Duty Cycle Range =100%→1.2% at 100Hz

3591f

10

LT3591

APPLICATIONS INFORMATION

LOW INPUT VOLTAGE APPLICATIONS

BOARD LAYOUT CONSIDERATIONS

As with all switching regulators, careful attention must be

paid to the PCB board layout and component placement.

To prevent electromagnetic interference (EMI) problems,

properlayoutofhighfrequencyswitchingpathsisessential.

Minimize the length and area of all traces connected to

the switching node pin (SW). Keep the sense voltage pins

The LT3591 can be used in low input voltage applications.

The input supply voltage to the LT3591 must be 2.5V or

higher.However,theinductorcanberunoffalowerbattery

voltage. This technique allows the LEDs to be powered off

two alkaline cells. Most portable devices have a 3.3V logic

supply voltage which can be used to power the LT3591.

TheLEDscanbedrivenstraightfromthebattery, resulting

in higher efﬁciency.

(CAP and LED) away from the switching node. Place C

OUT

next to the CAP pin. Always use a ground plane under the

switching regulator to minimize interplane coupling. Re-

commended component placement is shown in Figure 11.

Figure 10 shows six LEDs powered by two AA cells. The

batteryisconnectedtotheinductorandthechipispowered

off a 3.3V logic supply voltage.

C

IN

SHUTDOWN AND

V

IN

DIMMING CONTROL

CTRL

CAP

8

7

6

5

1

2

3

4

3.3V

CTRL CAP

V

IN

C1

1µF

LED

R

GND

9

SENSE

10Ω

LT3591

LED

L1

15µH

SW

C2

4.7µF

2 AA CELLS

2V TO 3.2V

SW

R

SENSE

GND

C

OUT

C1

1µF

3591 F11

3591 F10

C1: TAIYO YUDEN EMK107BJ105MA

C2: MURATA GRM31CR71H475KA12L

L1: TAIYO YUDEN NR4018T150M

Figure 11. Recommended Component Placement

Figure 10. 2 AA Cells to Six White LEDs

3591f

11

LT3591

TYPICAL APPLICATIONS

Li-Ion Driver for Ten White LEDs

Efﬁciency

D1

L1

85

80

75

70

65

60

55

22µH

*OPTIONAL

V

= 3.6V

IN

10 LEDs

SW

LT3591

GND

NO SCHOTTKY

V

IN

V

CAP

IN

3V TO 5V

R

SENSE

10Ω

SHUTDOWN

AND DIMMING

CONTROL

CTRL

LED

EXTERNAL SCHOTTKY

C2

2.2µF

C1

1µF

0

5

10

15

20

LED CURRENT (mA)

3491 TA02b

C1:TAIYO YUDEN EMK107BJ105MA

L1: TAIYO YUDEN NR4018T220M

C2: MURATA GRM31CR71H225KA88 D1: PHILLIPS PMEG4005AEA

Li-Ion Driver for Four White LEDs at 50mA

Efﬁciency

SHUTDOWN AND

80

75

70

65

60

DIMMING CONTROL

V

= 3.6V

IN

4 LEDs

CTRL

V

IN

V

CAP

LED

IN

3V TO 5V

R

L1

10µH

SENSE

LT3591

GND

3.92Ω

SW

C2

4.7µF

C1

1µF

20

LED CURRENT (mA)

0

10

30

40

50

C1:TAIYO YUDEN EMK107BJ105MA

C2: MURATA GRM31CR71H475KA12L

L1: MURATA LQH32CN100K53

3591 TA03b

3591f

12

LT3591

TYPICAL APPLICATIONS

24V to Four White LEDs at 100mA

Efﬁciency

95

90

85

80

75

70

C2

4.7µF

PV

IN

24V

R

SENSE

C3

2Ω

1µF

CAP

LED

V

3V

IN

L1

22µH

V

IN

C1

1µF

LT3591

GND

SHUTDOWN

AND

DIMMING

CONTROL

CTRL

SW

3591 TA05a

0

20

40

60

80

100

LED CURRENT (mA)

C1: TAIYO YUDEN EMK107BJ105MA

C2: MURATA GRM31CR71H475KA12L

C3: MURATA GRM21BR71H105KA12L

L1: TAIYO YUDEN NR4018T220M

3591 TA05b

24V to Five White LEDs at 100mA

Efﬁciency

C2

4.7µF

95

PV

IN

24V

R

SENSE

C3

1µF

90

85

80

75

70

2Ω

CAP

LED

V

IN

L1

22µH

V

IN

3V

C1

LT3591

GND

1µF

SHUTDOWN

AND

CTRL

SW

DIMMING

CONTROL

3591 TA06a

0

20

40

60

80

100

C1: TAIYO YUDEN EMK107BJ105MA

C2: MURATA GRM31CR71H475KA12L

C3: MURATA GRM21BR71H105KA12L

L1: TAIYO YUDEN NR4018T220M

LED CURRENT (mA)

3591 TA06b

3591f

13

LT3591

TYPICAL APPLICATIONS

Li-Ion Driver for Seven White LEDs

Conversion Efﬁciency

SHUTDOWN AND

85

80

75

70

65

60

55

50

DIMMING CONTROL

V

= 3.6V

IN

7 LEDs

CTRL

V

IN

V

CAP

LED

IN

3V TO 5V

L1

22µH

R

SENSE

10Ω

LT3591

GND

SW

C2

2.2µF

C1

1µF

0

5

10

20

15

LED CURRENT (mA)

3591 TA07b

3591 TA07a

C1: TAIYO YUDEN EMK107BJ105MA

C2: MURATA GRM31CR71H225KA88

L1: TAIYO YUDEN NR4018T220M

Li-Ion Driver for Eight White LEDs

Conversion Efﬁciency

SHUTDOWN AND

85

80

75

70

65

60

55

V

= 3.6V

IN

DIMMING CONTROL

8 LEDs

CTRL

V

IN

V

CAP

LED

IN

3V TO 5V

L1

22µH

R

SENSE

LT3591

GND

10Ω

SW

C2

2.2µF

C1

1µF

0

5

10

20

15

LED CURRENT (mA)

3591 TA08b

3591 TA08a

C1: TAIYO YUDEN EMK107BJ105MA

C2: MURATA GRM31CR71H225KA88

L1: TAIYO YUDEN NR4018T220M

3591f

14

LT3591

PACKAGE DESCRIPTION

DDB Package

8-Lead Plastic DFN (3mm × 2mm)

(Reference LTC DWG # 05-08-1702 Rev B)

0.61 0.05

(2 SIDES)

0.70 0.05

2.55 0.05

1.15 0.05

PACKAGE

OUTLINE

0.25 0.05

0.50 BSC

2.20 0.05

(2 SIDES)

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

R = 0.115

0.40 0.10

3.00 0.10

(2 SIDES)

TYP

5

R = 0.05

TYP

8

2.00 0.10

PIN 1 BAR

(2 SIDES)

TOP MARK

PIN 1

R = 0.20 OR

(SEE NOTE 6)

0.25 × 45°

0.56 0.05

(2 SIDES)

CHAMFER

4

1

(DDB8) DFN 0905 REV B

0.25 0.05

0.75 0.05

0.200 REF

0.50 BSC

2.15 0.05

(2 SIDES)

0 – 0.05

BOTTOM VIEW—EXPOSED PAD

NOTE:

1. DRAWING CONFORMS TO VERSION (WECD-1) IN JEDEC PACKAGE OUTLINE M0-229

2. DRAWING NOT TO SCALE

3. ALL DIMENSIONS ARE IN MILLIMETERS

4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE

MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE

5. EXPOSED PAD SHALL BE SOLDER PLATED

6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE

3591f

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 representa-

tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

15

LT3591

TYPICAL APPLICATION

Li-Ion Driver for Nine White LEDs

Conversion Efﬁciency

85

80

75

70

65

60

55

SHUTDOWN AND

V

= 3.6V

IN

DIMMING CONTROL

9 LEDs

CTRL

V

IN

V

CAP

LED

IN

3V TO 5V

L1

R

SENSE

C2

2.2µF

LT3591

GND

22µH

10Ω

SW

C1

1µF

20

0

5

10

15

LED CURRENT (mA)

3591 TA09b

3591 TA09a

C1: TAIYO YUDEN EMK107BJ105MA

C2: MURATA GRM31CR71H225KA88

L1: TAIYO YUDEN NR4018T220M

RELATED PARTS

PART NUMBER

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COMMENTS

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Up to 16 White LEDs, V : 1.6V to 18V, V

= 34V,

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I = 1.8mA, I < 1µA, MS Package

Q

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SD

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IN

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SD

MS Package

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IN

Q

SD

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LTC3205

High Efﬁciency, Multidisplay LED Controller

Up to 4 (Main), 2 (Sub) and RGB, V : 2.8V to 4.5V,

IN

I = 50µA, I < 1µA, 24-Lead QFN Package

Q

SD

LT3465/LT3465A

LT3466/LT3466-1

LT3486

Constant-Current, 1.2MHz/2.7MHz, High Efﬁciency White LED Up to 6 White LEDs, V : 2.7V to 16V, V

= 34V,

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Boost Regulator with Integrated Schottky Diode

I = 1.9mA, I < 1µA, ThinSOT Package

Q SD

Dual Full Function, 2MHz Diodes White LED Step-Up Converter Up to 20 White LEDs, V : 2.7V to 24V, V

= 39V,

IN

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with Built-In Schottkys

DFN, TSSOP-16 Packages

Dual 1.3A White LED Converter with 1000:1 True Color PWM

Dimming

Drives Up to 16 100mA White LEDs. V : 2.5V to 24V,

OUT(MAX)

IN

V

= 36V, DFN, TSSOP Packages

LT3491

2.3MHz White LED Driver with Integrated Schottky Diode

Drives Up to 6 LEDs. V : 2.5V to 12V, V

= 27V, SC70 and

= 32V,

OUT(MAX)

IN

OUT(MAX)

DFN Packages

LT3497

Dual Full Function 2.3MHz LED Driver with 250:1 True Color

PWM Dimming with Integrated Schottky Diodes

Up to 12 White LEDs, V : 2.5V to 10V, V

IN

3mm × 2mm DFN Package

ThinSOT is a trademark of Linear Technology Corporation

3591f

LT 0207 • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

16

●

(408) 432-1900 FAX: (408) 434-0507 www.linear.com


型号：	CDRH3D18-220NC
厂家：	Linear Systems
描述：	White LED Driver with Integrated Schottky in 3mm 2mm DFN 白光LED驱动器，集成肖特基采用3mm 2mm DFN封装驱动器
文件：	总16页 (文件大小：274K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

CDRH3D18-220NC [Linear Systems]

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