LT3466-1_技术文档

LT3498

20mA LED Driver and

OLED Driver with Integrated

Schottky in 3mm x 2mm DFN

DESCRIPTION

FEATURES

The LT^®3498 is a dual output boost converter featuring a

2.3MHzPWMLEDDriverandPFMOLEDDriver.Itincludes

an internal power switch and Schottky diode for each

driver. Both converters can be independently shut down

and modulated. This highly integrated power solution is

ideal for dual display electronic devices.

■

Dual Output Boost for Dual Display Devices

■

Drives Up to Six White LEDs and OLED/LCD Bias

■

Internal Power Switches and Schottky Diodes

■

Independent Dimming and Shutdown

■

200mV High Side Sense on LED Driver Allows

“One-Wire Current Source”

■

Wide Input Voltage Range: 2.5V to 12V

The2.3MHzstep-upconverterisdesignedtodriveuptosix

white LEDs in series from a Li-Ion cell. The device features

a unique high side LED current sense that enables the part

tofunctionasa“one-wire”currentsource—onesideofthe

LEDstringcanbereturnedtogroundanywhere.Traditional

LED drivers use a grounded resistor to sense LED current,

requiring a 2-wire connection to the LED string.

■

Wide Output Voltage Range: Up to 32V

■

2.3MHz PWM Frequency for LED Driver

■

PFM for OLED Driver is Non-Audible Over Entire

Load Range

■

Open LED Protection (27V Maximum on CAP1 Pin)

■

OLED Output Disconnect

■

Available in 12-Pin DFN Package

■

The PFM OLED driver is a low noise boost converter that

featuresanovelcontroltechnique.*Theconvertercontrols

power delivery by varying both the peak inductor current

and switch off time. This technique results in low output

voltage ripple, as well as, high efﬁciency over a wide load

range. The off time of the switch is not allowed to exceed a

ﬁxed level, guaranteeing a switching frequency that stays

above the audio band.

1mm Tall Solution Height

APPLICATIONS

■

Cellular Phones

■

PDAs, Handheld Computers

■

Digital Cameras

■

MP3 Players

■

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

All other trademarks are the property of their respective owners.

GPS Receivers

*Patent Pending

TYPICAL APPLICATION

Li-Ion to Six White LEDs and OLED/LCD Bias

OLED Efﬁciency

80

75

70

65

60

55

50

45

40

400

350

300

250

200

150

100

50

V

= 3V TO 5V

V

= 3.6V

IN

OUT2

4.7µF

0.47µF

= 16V

LOAD FROM V

OUT2

15µH

16V

24mA

1µF

CAP1 SW1

V

SW2 CAP2 V

OUT2

IN

LT3498

LED1 CTRL1 GND1 GND2 CTRL2 FB2

OFF OFF

10Ω

10µF

2.21MΩ

20mA

ON

POWER LOSS

FROM V

SHUTDOWN

AND

DIMMING

CONTROL

SHUTDOWN

AND

OUT2

CONTROL

0

100

0.1

1

10

3498 TA01

LED CURRENT (mA)

3498 TA01b

3498f

1

LT3498

ABSOLUTE MAXIMUM RATINGS

PACKAGE/ORDER INFORMATION

(Notes 1, 2)

TOP VIEW

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

IN

1

2

3

4

5

6

LED1

CTRL1

GND1

GND2

CTRL2

FB2

12 CAP1

11 SW1

CTRL1 and CTRL2 Voltage........................................12V

FB2 Voltage..............................................................2.5V

10

9

V

IN

13

V

OUT2

Voltage ...........................................................32V

SW2

SW1 and SW2 Voltage..............................................32V

CAP1 and CAP2 Voltage............................................32V

LED1 Voltage ............................................................32V

Operating Junction Temperature Range...–40°C to 85°C

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

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

8

CAP2

7

V

OUT2

DDB PACKAGE

12-LEAD (3mm × 2mm) PLASTIC DFN

= 125°C, θ = 160°C/W

T

JMAX

JA

EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB

ORDER PART NUMBER

LT3498EDDB

DDB PART MARKING

LCQF

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

= V

= 3V.

A

IN

CTRL1

CTRL2

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

V

Minimum Operating Voltage

Maximum Operating Voltage

Supply Current (LED Off, OLED Off)

Supply Current (LED On, OLED Off)

2.5

12

10

2

V

= 3V, V

= 0V, V

= 3V, V

= 0V

8

µA

IN

CTRL1

CTRL2

V

IN

V

= 0V, V

= 24V,

1.6

mA

CTRL1

= 23V

CAP1

LED1

Supply Current (LED Off, OLED On)

Supply Current (LED On, OLED On)

V

= 3V, V

= 0V, V

= 3V, V

= 3V, V = 3V

230

280

µA

IN

CTRL1

CTRL2

FB2

V

= 3V, V

= 24V,

1.65

2.05

mA

IN

LED1

CTRL1

CAP1

= 23V

●

V

for Full LED Current

1.5

V

CTRL1

CTRL2

CTRL1

for Full OLED Brightness

●

or V

to Turn On I

125

mV

nA

CTRL2

C

V

and V

to Shut Down I

75

CTRL1

CTRL2

C

CTRL1, CTRL2 Pin Bias Current

100

LED Driver

●

LED Current Sense Voltage (V

– V

)

LED

V

= 24V, I = 200mA

190

200

20

210

30

mV

µA

CAP

CAP1

SW

CAP1, LED1 Pin Bias Current

= 16V, V

= 16V

CAP1

LED1

V

, V

Common Mode Minimum Voltage

2.5

2.8

V

CAP1 LED1

●

Switching Frequency

Maximum Duty Cycle

Switch Current Limit

1.8

88

2.3

90

MHz

%

300

425

250

mA

Switch V

I

= 200mA

SW

mV

CESAT

3498f

2

LT3498

ELECTRICAL CHARACTERISTICS ^The

●

denotes the speciﬁcations which apply over the full operating

= V = 3V.

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

A

IN

CTRL1

CTRL2

PARAMETER

CONDITIONS

MIN

TYP

0.1

27

MAX

5

UNITS

µA

V

Switch Leakage Current

CAP1 Pin Overvoltage Protection

Schottky Forward Voltage

Schottky Reverse Leakage

OLED Driver

V

SW1

= 16V

26

28

I

= 100mA

= 20V

0.8

V

SCHOTTKY1

V

6

µA

REVERSE1

●

Feedback Voltage

V

= 3V (Note 3)

1.18

177

1.215

182

150

1

1.25

186

V

kΩ

ns

CTRL2

Feedback Resistor

Minimum Switch Off Time

Maximum Switch Off Time

Switch Current Limit

After Start-Up

During Start-Up (Note 4)

µs

●

V

FB2

= 1.5V

15

20

30

µs

180

300

260

0.1

400

mA

mV

µA

mV

µA

mV

µA

Switch V

I

= 200mA

= 16V

CESAT

SW2

Switch Leakage Current

Schottky Forward Voltage

Schottky Reverse Leakage

V

SW2

5

2

I

= 100mA

= 20V

800

SCHOTTKY2

V

REVERSE2

OUT2

PMOS Disconnect V

CTRL2 to FB2 Offset

– V

I

= 10mA, V = 5V

CAP2

250

8

CAP2

OUT2

V

= 0.5V

15

CTRL2

Maximum Shunt Current

= 1.3V

220

FB2

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 3: Internal reference voltage is determined by ﬁnding V voltage

level which causes quiescent current to increase 20µA above “Not

Switching” level.

FB2

Note 4: If CTRL2 is overriding the internal reference, start-up mode

Note 2: The LT3498 is guaranteed to meet performance speciﬁcations

from 0°C to 85°C. Speciﬁcations over the –40°C to 85°C junction

operating temperature range are assured by design, characterization and

correlation with statistical process controls.

occurs when V is less then half the voltage on CTRL2. If CTRL2 is not

FB2

overriding the internal reference, start-up mode occurs when V is less

FB2

then half the voltage of the internal reference.

3498f

3

LT3498

TYPICAL PERFORMANCE CHARACTERISTICS

T = 25°C, unless otherwise speciﬁed.

A

Shutdown Current

LED Switch Saturation

Voltage (V

LED Schottky Forward

Voltage Drop

(V

= V

= 0V)

)

CESAT1

CTRL1

CTRL2

500

450

400

350

300

250

200

150

100

50

15

12

9

400

T = –50°C

350

T = –50°C

T = 125°C

300

250

T = 25°C

T = 125°C

200

150

T = 125°C

T = 25°C

6

100

50

0

3

0

T = –50°C

0

4

6

8

10

12

2

0

50 100 150 200 250 300 350 400

SWITCH CURRENT (mA)

200

400

800

0

1000

600

V

(V)

IN

SCHOTTKY FORWARD DROP (mV)

3498 G03

1635 G07

3498 G02

Sense Voltage (V

– V

)

Sense Voltage (V

vs Temperature

– V

)

Sense Voltage (V

– V

)

CAP1

LED1

CAP1

LED1

CAP1

LED1

vs V

CAP1

CTRL1

206

202

198

194

190

186

206

202

198

194

190

186

240

200

T = 25°C

T = –50°C

T = 125°C

160

120

T = 125°C

T = 25°C

T = –50°C

80

40

0

–50 –25

0

25

50

75 100 125

0

5

15

CAP1 VOLTAGE (V)

20

25

10

0

500

V

1000

(mV)

1500

2000

TEMPERATURE (°C)

CTRL1

3498 G06

3498 G04

3498 G05

LED Current Limit

vs Temperature

Open Circuit Output

Clamp Voltage

Input Current in Output

Open Circuit

6

5

500

450

400

350

300

29

28

27

26

25

T = –50°C

T = 150°C

T = 25°C

4

3

T = 25°C

T = –50°C

2

1

0

2

4

6

8

10

12

–50 –25

0

25

50

75 100 125

0

4

6

8

10

12

2

V

(V)

TEMPERATURE (°C)

V

(V)

IN

3498 G09

3498 G07

3498 G08

3498f

4

LT3498

TYPICAL PERFORMANCE CHARACTERISTICS

T = 25°C, unless otherwise speciﬁed.

A

LED Switching Frequency

vs Temperature

OLED Switch Saturation

Voltage (V

OLED Schottky Forward

Voltage Drop

)

CESAT2

300

250

200

150

100

50

2.6

400

350

300

250

T = 125°C

2.5

2.4

T = 125°C

T = –50°C

T = 25°C

2.3

2.2

2.1

2.0

1.9

200

150

T = 25°C

100

50

0

T = –50°C

0

1.8

0

100

150

200

250

300

50

–25

0

50

75 100 125

200

400

800

–50

25

0

1000 1200

600

SWITCH CURRENT (mA)

TEMPERATURE (°C)

SCHOTTKY FORWARD DROP (mV)

3498 G12

3498 G11

3498 G10

V

vs V

OUT2

V

vs Temperature

= 16V)

OUT2

CTRL2

OUT2

(V

= 16V)

(V

V

Load Regulation

OUT2

6

3

18

16

14

12

10

8

2.0

1.5

1.0

0.5

0

–0.5

6

–3

–1.0

–1.5

–2.0

4

2

–6

0

–50 –25

0

25

50

75 100 125

0

2000

10

20

LOAD CURRENT (mA)

40

500

1000

1500

0

50

30

TEMPERATURE (°C)

CTRL2 VOLTAGE (V)

3498 G13

3498 G14

3498 G15

OLED Minimum

OLED Switching Frequency

vs Load Current

Switching Frequency

Peak Inductor Current

1200

1000

800

600

400

200

0

80

600

70

60

550

500

50

40

30

20

10

450

400

350

300

250

0

200

0.1

1

10

100

–25

0

50

75 100 125

–50

25

–25

0

50

75 100 125

–50

25

LOAD CURRENT (mA)

TEMPERATURE (°C)

3498 G17

3498 G16

3498 G18

3498f

5

LT3498

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

A

OLED Switching Waveforms

with No Load

LED Switching Waveforms

LED Transient Response

V

OUT2

10mV/DIV

V

CAP1

5V/DIV

SW

AC COUPLED

10V/DIV

V

CTRL1

SW2 VOLTAGE

V

CAP1

5V/DIV

10V/DIV

50mV/DIV

I

L

I

L

INDUCTOR

CURRENT

50mA/DIV

100mA/

DIV

200mA/

DIV

3498 G19

3498 G20

3498 G21

500ns/DIV

1ms/DIV

5µs/DIV

V

= 3.6V

V = 3.6V

IN

V

= 3.6V

IN

OUT2

FRONT PAGE APPLICATION

= 16V

OLED Switching Waveforms

with 35mA Load

OLED Switching Waveforms

During Start-Up

OLED Switching Waveforms

with 4mA Load

V

CAP2

VOLTAGE

5V/DIV

OUT2

V

OUT2

10mV/DIV

AC

10mV/DIV

AC COUPLED

COUPLED

V

SW2

VOLTAGE

10V/DIV

OUT2

SW2

VOLTAGE

10V/DIV

VOLTAGE

5V/DIV

INDUCTOR

CURRENT

200mA/DIV

INDUCTOR

CURRENT

100mA/DIV

INDUCTOR

CURRENT

200mA/DIV

3498 G24

3498 G23

3498 G22

500µs/DIV

500ns/DIV

2µs/DIV

V

= 3.6V

V

= 3.6V

IN

OUT2

V

= 3.6V

IN

OUT2

IN

OUT2

= 16V

PIN FUNCTIONS

LED1 (Pin 1): Connection Point Between the Anode of the

Highest LED and the Sense Resistor. The LED current can

be programmed by:

CTRL2 (Pin 5): Dimming and Shutdown Pin. Connect it

below 75mV to disable the low noise boost converter.

As the pin voltage is ramped from 0V to 1.5V, the output

ramps up to the programmed output voltage.

200mV

R_SENSE1

I_LED1

=

FB2 (Pin 6): Feedback Pin. Reference voltage is 1.215V.

There is an internal 182kΩ resistor from FB2 to GND. To

CTRL1 (Pin 2): Dimming and Shutdown Pin. Connect this

pin below 75mV to disable the white LED driver. As the

pin voltage is ramped from 0V to 1.5V, the LED current

achieve desired output voltage, choose R according to

FB2

the following formula:

V

⎛

⎞

OUT2

ramps from 0 to (I

= 200mV / R

).

R_FB2=182•

−1 kΩ

LED1

SENSE1

⎜

⎝

⎟

⎠

1.215

GND1, 2 (Pins 3, 4): Ground. Tie directly to local ground

plane. GND1 and GND2 are connected internally.

3498f

6

LT3498

PIN FUNCTIONS

V

(Pin 7): Drain of Output Disconnect PMOS.

SW1 (Pin 11): Switch Pin. Connect the inductor of the

white LED driver at this pin. Minimize metal trace area at

this pin to minimize EMI.

OUT2

Place a bypass capacitor from this pin to GND. See the

Applications Information section.

CAP2 (Pin 8): Output of the OLED Driver. This pin is

connected to the cathode of the internal Schottky diode.

Place a bypass capacitor from this pin to GND.

CAP1 (Pin 12): Output of the White LED Driver. This pin is

connectedtothecathodeoftheinternalSchottky. Connect

theoutputcapacitortothispinandthesenseresistorfrom

this pin to the LED1 pin.

SW2 (Pin 9): Switch Pin. This is the collector of the in-

ternal NPN power switch. Minimize the metal trace area

connected to this pin to minimize EMI.

Exposed Pad (Pin 13): Ground. The Exposed Pad must

be soldered to the PCB.

V

(Pin 10): Input Supply Pin. Must be locally by-

IN

passed.

BLOCK DIAGRAM

L2

10µF

L1

15µF

C

IN

4.7µF

9

10

V

11

SW1

CAP1

SW2

COMPARATOR

IN

12

CAP2

–

+

8

R

Q

Q1

A2

S

C2

0.47µF

OVERVOLTAGE

PROTECTION

START-UP

CONTROL

DRIVER

A3

+

–

R

SENSE1

10Ω

Σ

RAMP

GENERATOR

C1

1µF

V

OUT2

7

DRIVER

2.3MHz

OSCILLATOR

+

SWITCH

CONTROL

C3

10µF

Q2

–

+

A4

LED1

DISCONNECT

CONTROL

1

–

A1

R

C

SHUNT

CONTROL

C

R

FB2

2.21MΩ

+

VREF

+

A5

–

182kΩ

GND2

FB2

CTRL2

CTRL1 GND1

2 3

4

6

5

3498 BD

3498f

7

LT3498

OPERATION—LED DRIVER

The LED portion of the LT3498 uses a constant-frequency,

current mode control scheme to provide excellent line

and load regulation. Operation can be best understood

by referring to the Block Diagram.

reduced, the device will begin skipping pulses. This will

result in some low frequency ripple, although the average

LED current remains regulated down to zero. The photo in

Figure 1 details circuit operation driving four white LEDs

at 2mA load. Peak inductor current is less than 60mA and

the regulator operates in discontinuous mode, meaning

the inductor current reaches zero during the discharge

phase. After the inductor current reaches zero, the SW1

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 CAP1 pin is charged up

to V (input supply voltage) through the inductor and the

IN

internal Schottky diode. If CTRL1 is pulled higher than

125mV, 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

I

L

50mA/DIV

the difference between the V

and V

voltage and

CAP1

LED1

the 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 CTRL1 pin is used to

adjust the LED current. The LED Driver is shutdown when

CTRL1 is pulled lower than 75mV.

V

SW

10V/DIV

3498 F01

200ns/DIV

V

= 4.2V

IN

I

= 2mA

LED

4 LEDs

Minimum Output Current

Figure 1. Switching Waveforms with

Four White LEDs at 2mA Load

The LED Driver of the LT3498 can drive a 4-LED string at

2mA LED current, without pulse-skipping, using the same

external components shown in the application circuit on

the front page of this data sheet. As current is further

3498f

8

LT3498

OPERATION—OLED DRIVER

The low noise boost of the LT3498 uses a novel control

scheme to provide high efﬁciency over a wide range

of output current. In addition, this technique keeps the

switching frequency above the audio band over all load

conditions.

parameters to achieve regulation. During the start-up of

the circuit, special precautions are taken to ensure that

the inductor current remains under control.

Because the switching frequency is never allowed to fall

below approximately 50kHz, a minimum load must be

present to prevent the output voltage from drifting too

high.Thisminimumloadisautomaticallygeneratedwithin

thepartviatheShuntControlblock.Thelevelofthiscurrent

is adaptable, removing itself when not needed to improve

efﬁciency at higher load levels.

The operation of the part can be better understood by

referring to the Block Diagram. The part senses the

output voltage by monitoring the voltage on the FB2 pin.

The user sets the desired output voltage by choosing the

value of the external topside feedback resistor. The part

incorporates a precision 182kΩ bottom-side feedback

resistor. Assuming that output voltage adjustment is not

used (CTRL2 pin is tied to 1.5V, or greater), the internal

The low-noise boost of the LT3498 also has an integrated

Schottky diode and PMOS output disconnect switch. The

PMOS switch is turned on when the part is enabled. When

thepartisinshutdown,thePMOSswitchturnsoff,allowing

reference (V

= 1.215V) sets the voltage to which FB2

REF

will servo during regulation.

the V

node to go to ground. This type of disconnect

OUT2

The Switch Control block senses the output of the ampli-

ﬁer and adjusts the switching frequency, as well as other

function is often required in power supplies.

APPLICATIONS INFORMATION—LED DRIVER

80

Inductor Selection

75

A 15µH inductor is recommended for most applications

70

for the LED driver of the LT3498. Although small size and

high efﬁciency are major concerns, the inductor should

65

have low core losses at 2.3MHz and low DCR (copper

60

wire resistance). Some small inductors in this category

15uH Murata LQH32CN150K53

15uH Murata LQH2MCN150K02

15uH Cooper SD3110-150

15uH Toko D312C

55

are listed in Table 1. The efﬁciency comparison of different

inductors is shown in Figure 2.

50

15uH Coilcraft DO3314-153ML

Table 1: Recommended Inductors

45

5

10

20

0

15

MAX

DCR

(Ω)

CURRENT

RATING

(mA)

LED CURRENT (mA)

L

(µH)

3498 F02

PART

VENDOR

Figure 2. Efﬁciency Comparison of Different Inductors

LQH32CN150K53

LQH2MCN150K02

LQH32CN100K53

LQH2MCN100K02

15

10

0.58

1.6

0.3

1.2

300

200

450

225

Murata

www.murata.com

Capacitor Selection

The small size of ceramic capacitors makes them ideal for

LT3498 LED driver applications. Use only X5R and X7R

types, because they retain their capacitance over wider

temperature ranges than other types, such as Y5V or

Z5U. A 4.7µF input capacitor and a 1µF output capacitor

are sufﬁcient for most applications.

SD3110-150

15

0.764

380

Cooper

www.cooperet.com

1001AS-150M

(TYPE D312C)

15

0.80

0.86

360

680

Toko

www.toko.com

D03314-153ML

Coilcraft

www.coilcraft.com

3498f

9

LT3498

APPLICATIONS INFORMATION—LED DRIVER

Inrush Current

Table 2: Recommended Ceramic Capacitor Manufacturers

Taiyo Yuden

(800) 368-2496

The LT3498 LED Driver has a built-in Schottky diode.

www.t-yuden.com

When supply voltage is applied to the V pin, an inrush

IN

AVX

(803) 448-9411

www.avxcorp.com

current ﬂows through the inductor and Schottky diode

and charges up the CAP1 voltage. The Schottky diode

for the LED Driver of the LT3498 can sustain a maximum

current of 1A.

Murata

(714) 852-2001

www.murata.com

Overvoltage Protection

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

application, the peak inrush current can be simpliﬁed as

follows:

The LED driver of the LT3498 has an internal open-circuit

protectioncircuit.Inthecasesofoutputopencircuit,when

the LEDs are disconnected from the circuit or the LEDs

fail open-circuit, V

driver will then switch at a very low frequency to minimize

input current. The V and input current during output

open-circuit are shown in the Typical Performance Char-

acteristics. Figure 3 shows the transient response when

the LEDs are disconnected.

r

α =

is clamped at 27V (typ). The LED

CAP1

2•L

r²

4•L²

CAP1

1

L •C

ω =

–

V – 0.6

L •ω

α π

• exp – •

⎛

⎝

⎞

IN

I_PK

=

⎜

⎟

⎠

ω 2

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

and C is the output capacitance.

I

L

200mA/DIV

Table 3 gives inrush peak currents for some component

selections.

Table 3: Inrush Peak Currents

V

CAP1

LEDs DISCONNECTED

AT THIS POINT

10V/DIV

3498 F03

V

(V)

r (Ω)

L (µH)

C

(µF)

I (A)

P

IN

OUT

500µs/DIV

V

= 3.6V

IN

4.2

0.58

1.6

15

1

0.828

0.682

0.794

0.803

FRONT PAGE APPLICATION CIRCUIT

4.2

1

Figure 3. Transient Response with

LEDs Disconnected From Output

0.8

0.739

3498f

10

LT3498

APPLICATIONS INFORMATION—LED DRIVER

Programming LED Current

The LED current can be set by:

The feedback resistor (R

) and the sense voltage

200mV

SENSE1

I_LED

≈

, when V_CTRL1>1.5V

(V

– V

) control the LED current. The CTRL1 pin

CAP1

LED1

R_SENSE1

V_CTRL1

6.25•R_SENSE1

controls the sense reference voltage as shown in the

Typical Performance Characteristics. For CTRL1 higher

than 1.5V, the sense reference is 200mV, which results in

full LED current. To have accurate LED current, precision

resistorsarepreferred(1%isrecommended).Theformula

I_LED

, when V_CTRL1<1.25V

Feedback voltage variation versus control voltage is

given in the Typical Performance Characteristics.

and table for R

selection are shown below.

SENSE

200mV

I_LED

Using a Filtered PWM Signal

R_SENSE1

=

A ﬁltered PWM signal can be used to control the bright-

ness of the LED string. The PWM signal is ﬁltered (Figure 4)

by a RC network and fed to the CTRL1 pin.

Table 4: R

Value Selection for 200mV Sense

SENSE1

(mA)

I

R

(Ω)

LED

SENSE1

5

40

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 CTRL1

pin which is 10MΩ (typ).

10

15

20

13.3

10

Dimming Control

Therearethreedifferenttypesofdimmingcontrolcircuits.

The LED current can be set by modulating the CTRL1 pin

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

a PWM signal.

LT3498

R1

100kΩ

PWM

10kHz TYP

CTRL1

3498 F04

C1

0.1µF

Using a DC Voltage

Forsomeapplications,thepreferredmethodofbrightness

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

The CTRL1 pin voltage can be modulated to set the dim-

ming of the LED string. As the voltage on the CTRL1 pin

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

Figure 4. Dimming Control Using a Filtered PWM Signal

0toI . AstheCTRL1pinvoltageincreasesbeyond1.5V,

LED

it has no effect on the LED current.

3498f

11

LT3498

APPLICATIONS INFORMATION—LED DRIVER

Direct PWM Dimming

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

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.

are connected to ground and a current of I

SENSE1

= 200mV /

LED

R

ﬂows through the LEDs. When the 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 6 shows the PWM dimming

waveforms for the circuit in Figure 5.

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.

I

LED

20mA/DIV

I

L

200mA/DIV

PWM

5V/DIV

3498 F06

2ms/DIV

V

= 3V

IN

4 LEDs

Figure 5 shows a Li-Ion powered driver for four white

LEDs. Direct PWM dimming method requires an external

NMOS tied between the cathode of the lowest LED in the

string and ground as shown in Figure 5. A simple logic

level Si2304 MOSFET can be used since its source is

connected to ground. The PWM signal is applied to the

CTRL1 pin of the LT3498 and the gate of the MOSFET.

Figure 6. Direct PWM Dimming Waveforms

80

V

= 3.4V

IN

4 LEDs

75

100Hz = PWM

V

IN

3V TO 5V

C

IN

R

70

65

SENSE1

10Ω

1µH

L1

15µH

CAP1 SW1

V

SW2 CAP2 V

IN OUT2

60

55

50

LT3498

C

OUT1

1µF

LED1

CTRL1

CTRL2

FB2

GND1

GND2

Q1

Si2304BDS

0

2

4

6

8

10 12 14 16 18 20

LED CURRENT (mA)

5V

0V

100k

3498 F07

3498 F05

Figure 7. PWM Dimming Efﬁciency

PWM

FREQ

Figure 5. Li-Ion to Four White LEDs

with Direct PWM Dimming

3498f

12

LT3498

APPLICATIONS INFORMATION—LED DRIVER

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 6 is approximately 40µs for a

3V input voltage. The achievable dimming range for this

application and 100Hz PWM frequency can be determined

using the following method.

The dimming range can be further extended by changing

the amplitude of the PWM signal. The height of the PWM

signalsetsthecommandedsensevoltageacrossthesense

resistorthroughtheCTRL1pin.Inthismannerbothanalog

dimming and direct PWM dimming extend the dimming

range for a given application. The color of the LEDs no

longer remains constant because the forward current of

the LED changes with the height of the CTRL1 signal. For

the four LED application described above, the LEDs can

be dimmed ﬁrst, modulating the duty cycle of the PWM

signal.Oncetheminimumdutycycleisreached,theheight

of the PWM signal can be decreased below 1.5V down to

125mV. The use of both techniques together allows the

average LED current for the four LED application to be

variedfrom20mAdowntolessthan20µA. Figure9shows

the application for dimming using both analog dimming

and PWM dimming. A potentiometer must be added to

ensure that the gate of the NMOS receives a logic-level

signal, while the CTRL1 signal can be adjusted to lower

amplitudes.

Example:

f = 100Hz, t_SETTLE= 40µs

1

f

1

100

t_PERIOD= =

= 0.01s

0.01s

t_SETTLE40µs

t_PERIOD

DimRange =

=

= 250 :1

MinDuty Cycle =

40µs

0.01s

t_SETTLE

t_PERIOD

• 100 =

• 100 = 0.4%

Duty Cycle Range = 100% → 0.4% at 100Hz

V

IN

3V TO 5V

C

IN

1µH

R

Thecalculationsshowthatfora100Hzsignalthedimming

range is 250:1. In addition, the minimum PWM duty cycle

of 0.4% ensures that the LED current has enough time to

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

achievable for three different frequencies with a settling

time of 40µs.

SENSE1

10Ω

L1

15µH

CAP1 SW1

V

SW2 CAP2 V

IN OUT2

LT3498

C

OUT1

1µF

LED1

CTRL1

CTRL2

FB2

GND1

GND2

5V

0V

10000

PWM

FREQ

3498 F09

PULSING MAY BE VISIBLE

1000

100

10

Q1

Si2304BDS

100k

Figure 9. Li-Ion to Four White LEDs with

Both PWM Dimming and Analog Dimming

1

10

100

1000

10000

PWM FREQUENCY (Hz)

3498 F08

Figure 8. Dimming Ratio vs Freqeuncy

3498f

13

LT3498

APPLICATIONS INFORMATION—OLED DRIVER

Inductor Selection

Capacitor Selection

Several recommended inductors that work well with the

OLED driver of the LT3498 are listed in Table 5, although

there are many other manufacturers and devices that can

be used. Consult each manufacturer for more detailed

information and for their entire selection of related parts.

Many different sizes and shapes are available. Use the

equations and recommendations in the next few sections

to ﬁnd the correct inductance value for your design.

The small size and low ESR of ceramic capacitors makes

them suitable for most OLED Driver applications. X5R and

X7R types are recommended because they retain their ca-

pacitance over wider voltage and temperature ranges than

other types such as Y5V or Z5U. A 4.7µF input capacitor

and a 10µF output capacitor are sufﬁcient for most appli-

cations for the OLED Driver. Always use a capacitor with

a sufﬁcient voltage rating. Many capacitors rated at 10µF,

particularly 0805 or 0603 case sizes, have greatly reduced

capacitancewhenbiasvoltagesareapplied.Besuretocheck

actualcapacitanceatthedesiredoutputvoltage. Generally

a 1206 size capacitor will be adequate. A 0.47µF capaci-

tor placed on the CAP node is recommended to ﬁlter the

Table 5: Recommended Inductors

MAX

DCR

(Ω)

CURRENT

RATING

(mA)

L

(µH)

PART

VENDOR

LQH32CN100K53

LQH2MCN100K02

LQH32CN150K53

LQH2MCN150K02

10

15

0.3

1.2

0.58

1.6

450

225

300

200

Murata

www.murata.com

inductor current while the larger 10µF placed on the V

OUT

node will give excellent transient response and stability.

Table 6 shows a list of several capacitor manufacturers.

Consult the manufacturers for more detailed information

and for their entire selection of related parts.

SD3110-100

SD3110-150

10

15

0.505

0.764

470

380

Cooper

www.cooperet.com

Inductor Selection—Boost Regulator

Table 6. Recommended Ceramic Capacitor Manufacturers

The formula below calculates the appropriate inductor

value to be used for the low noise boost regulator of

the LT3498 (or at least provides a good starting point).

This value provides a good tradeoff in inductor size and

system performance. Pick a standard inductor close to

this value. A larger value can be used to slightly increase

the available output current, but limit it to around twice

the value calculated below, as too large of an inductance

will decrease the output voltage ripple without providing

much additional output current. A smaller value can be

used (especially for systems with output voltages greater

than 12V) to give a smaller physical size. Inductance can

be calculated as:

MANUFACTURER

Taiyo Yuden

AVX

PHONE

URL

408-573-4150

843-448-9411

814-237-1431

408-986-0424

www.t-yuden.com

www.avxcorp.com

www.murata.com

www.kemet.com

Murata

Kemet

Setting Output Voltage and the Auxiliary

Reference Input

The OLED driver of the LT3498 is equipped with both an

internal 1.215V reference and an auxiliary reference input.

This allows the user to select between using the built-in

reference, and supplying an external reference voltage.

The voltage at the CTRL2 pin can be adjusted while the

chip is operating to alter the output voltage of the LT3498

for purposes such as display dimming or contrast adjust-

ment. To use the internal 1.215V reference, the CTRL2 pin

must be held higher than 1.5V. When the CTRL2 pin is

held between 0V and 1.5V the OLED driver will regulate

the output such that the FB2 pin voltage is nearly equal to

theCTRL2pinvoltage. AtCTRL2voltagescloseto1.215V,

L = (V_OUT2− V_IN(MIN)+ 0.5V) • 0.66(µH)

where V

is the desired output voltage and V

is

OUT2

IN(MIN)

the minimum input voltage. Generally, a 10µH or 15µH

inductor is a good choice.

3498f

14

LT3498

APPLICATIONS INFORMATION—OLED DRIVER

a soft transition occurs between the CTRL2 pin and the

Choosing a Feedback Node

internal reference. Figure 10 shows this behavior.

ThesinglefeedbackresistormaybeconnectedtotheV

pin or to the CAP2 pin (see Figure 11). Regulating the

OUT2

1.500

1.250

1.000

0.750

0.500

0.250

0

V

pin eliminates the output offset resulting from the

OUT2

voltage drop across the output disconnect PMOS. Regu-

lating the CAP2 pin does not compensate for the voltage

drop across the output disconnect, resulting in an output

voltage V

that is slightly lower than the voltage set by

OUT2

the resistor divider. Under most conditions, it is advised

that the feedback resistor be tied to the V

pin.

OUT2

Connecting the Load to the CAP2 Node

0

0.5

0.8

1.0

1.3

1.5

0.3

The efﬁciency of the converter can be improved by con-

necting the load to the CAP2 pin instead of the V pin.

CTRL2 VOLTAGE (V)

OUT2

3498 F10

The power loss in the PMOS disconnect circuit is then

Figure 10. CTRL2 to FB2 Transfer Curve

made negligible. By connecting the feedback resistor to

the V

pin, no quiescent current will be consumed

OUT2

To set the maximum output voltage, select the values of

in the feedback resistor string during shutdown since

the PMOS transistor will be open (see Figure 12). The

disadvantage of this method is that the CAP2 node can-

not go to ground during shutdown, but will be limited to

R

FB2

according to the following equation:

V

⎛

⎞

OUT2

R_FB2=182•

–1 , kΩ

⎜

⎝

⎟

⎠

1.215

around a diode drop below V . Loads connected to the

IN

When CTRL2 is used to override the internal reference,

the output voltage can be lowered from the maximum

value down to nearly the input voltage level. If the voltage

source driving the CTRL2 pin is located at a distance to

the LT3498, a small 0.1µF capacitor may be needed to

bypass the pin locally.

part should only sink current. Never force external power

supplies onto the CAP2 or V

pins. The larger value

OUT2

output capacitor should be placed on the node to which

the load is connected.

I

CAP1

SW1

V

SW2

LT3498

LED1 CTRL1 GND1 GND2 CTRL2

CAP2

V

OUT2

CAP1

SW1

V

SW2

LT3498

LED1 CTRL1 GND1 GND2 CTRL2

CAP2

V

LOAD

C3

C2

IN

OUT2

IN

R

FB2

R

FB2

3498 F12

C2

Figure 12. Improved Efﬁciency

CAP1

SW1

V

SW2

LT3498

LED1 CTRL1 GND1 GND2 CTRL2

CAP2

V

C3

IN

OUT2

FB2

R

FB2

3498 F11

Figure 11. Feedback Connection Using

the CAP2 Pin or the V Pin

OUT2

3498f

15

LT3498

APPLICATIONS INFORMATION—OLED DRIVER

Maximum Output Load Current

Step 4: Calculate the nominal output current:

The maximum output current of a particular LT3498

circuit is a function of several circuit variables. The fol-

lowing method can be helpful in predicting the maximum

load current for a given circuit:

I_IN(AVG)• V_IN• 0.75

V_OUT2

I_OUT(NOM)

=

amps

Step 5: Derate output current:

= I • 0.7 amps

I

Step 1: Calculate the peak inductor current:

OUT

OUT(NOM)

V • 400 •10^–9

For low output voltages the output current capability will

beincreased. Whenusingoutputdisconnect(loadcurrent

IN

I_PK= I_LIMIT

where I

+

amps

L

taken from V

), these higher currents will cause the

OUT2

is 0.3A for the OLED driver. L is the induc-

drop in the PMOS switch to be higher resulting in reduced

output current capability than those predicted by the

preceding equations.

LIMIT

tance value in Henrys and V is the input voltage to the

IN

boost circuit.

Step 2: Calculate the inductor ripple current:

Inrush Current

V

+ 1– V • 150 • 10^–9

(

)

When V is stepped from ground to the operating voltage

OUT2

IN

I_RIPPLE

=

amps

while the output capacitor is discharged, a higher level of

inrushcurrentwillﬂowthroughtheinductorandintegrated

Schottky diode into the output capacitor. Conditions that

increaseinrushcurrentincludealargermoreabruptvoltage

L

where V

is the desired output voltage.

OUT2

If the inductor ripple current is less then the peak current,

then the circuit will only operate in discontinuous conduc-

tion mode. The inductor value should be increased so

step at V , a larger output capacitor tied to the CAP2 pin,

IN

and an inductor with a low saturation current. While the

internaldiodeisdesignedtohandlesuchevents,theinrush

current should not be allowed to exceed 1A. For circuits

that use output capacitor values within the recommended

range and have input voltages of less than 5V, inrush cur-

rent remains low, posing no hazard to the device. In cases

that I

< I . An application circuit can be designed

RIPPLE

PK

to operate only in discontinuous mode, but the output

current capability will be reduced.

Step 3: Calculate the average input current:

where there are large steps at V (more than 5V) and/or

IN

I_RIPPLE

I_IN(AVG)= I_PK

–

amps

a large capacitor is used at the CAP2 pin, inrush current

2

should be measured to ensure safe operation.

3498f

16

LT3498

APPLICATIONS INFORMATION—LED AND OLED DRIVER

Board Layout Considerations

node. The FB2 connection for the feedback resistor R

FB2

should be tied directly from the V

pin to the FB2

OUT2

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 pins (SW1 and SW2). Keep the sense

voltage pins (CAP1 and LED1) away from the switching

pin and be kept as short as possible, ensuring a clean,

noise-free connection. Place C and C next to the

OUT1

OUT2

CAP1 and CAP2 pins respectively. Always use a ground

planeendertheswitchingregulatortominimizeinterplane

coupling. Recommendedcomponentplacementisshown

in Figure 13.

R

SENSE1

LED1

CAP1

C1

SW1

1

2

3

4

5

6

12

11

10

9

CTRL1

GND

L1

L2

GND

V

IN

C

IN

CTRL2

SW2

8

7

R

FB2

C3

C2

V

OUT2

FB2

V

OUT2

CAP2

3498 F13

GND

VIAS TO GROUND PLANE REQUIRED TO

IMPROVE THERMAL PERFORMANCE

VIAS TO V

OUT2

Figure 13. Recommended Board Layout

3498f

17

LT3498

TYPICAL APPLICATIONS

Li-Ion to Two White LEDs and OLED/LCD Bias

V

= 3V TO 5V

C

C2

0.47µF

IN

4.7µF

C1

1µF

L1

10µH

L2

10µH

16V

24mA

CAP1 SW1

V

SW2

CAP2 V

OUT2

C3

10µF

IN

LT3498

20mA

R

FB2

LED1 CTRL1 GND1 GND2 CTRL2

FB2

2.21MΩ

R

SENSE1

OFF

ON

10Ω

ON

SHUTDOWN

AND

3498 TA02

DIMMING

CONTROL

C

, C2: X5R OR X7R WITH SUFFICIENT VOLTAGE RATING

IN

C1: TAIYO YUDEN GMK212BJ105KG

C3: TAIYO YUDEN TMK316BJ106ML

L1, L2: MURATA LQH32CN100K53

LED Efﬁciency

IN

V

= 3.6V, 2 LEDs

75

70

65

60

55

50

45

40

0

5

10

20

15

LED CURRENT (mA)

3498 TA02b

3498f

18

LT3498

TYPICAL APPLICATIONS

Li-Ion to Two White LEDs and OLED/LCD Bias

V

= 3V TO 5V

C

C2

0.47µF

IN

4.7µF

L1

10µH

L2

10µH

16V

24mA

CAP1 SW1

V

SW2

CAP2 V

OUT2

C3

10µF

IN

C1

1µF

LT3498

R

SENSE1

FB2

LED1 CTRL1 GND1 GND2 CTRL2

OFF OFF

FB2

10Ω

2.21MΩ

ON

SHUTDOWN

AND

20mA

DIMMING

CONTROL

3498 TA03

C

, C2: X5R OR X7R WITH SUFFICIENT VOLTAGE RATING

IN

C1: TAIYO YUDEN GMK212BJ105KG

C3: TAIYO YUDEN TMK316BJ106ML

L1, L2: MURATA LQH32CN100K53

LED Efﬁciency

= 3.6V, 2 LEDs

V

IN

80

75

70

65

60

55

50

45

40

0

5

10

20

15

LED CURRENT (mA)

3498 TA03b

3498f

19

LT3498

TYPICAL APPLICATIONS

Li-Ion to Three White LEDs and OLED/LCD Bias

V

= 3V TO 5V

C

C2

0.47µF

IN

4.7µF

L1

15µH

L2

10µH

16V

24mA

CAP1 SW1

V

SW2

CAP2 V

OUT2

C3

10µF

IN

C1

1µF

LT3498

R

SENSE1

FB2

LED1 CTRL1 GND1 GND2 CTRL2

OFF OFF

FB2

10Ω

2.21MΩ

ON

SHUTDOWN

AND

20mA

DIMMING

CONTROL

3498 TA04

C

, C2: X5R OR X7R WITH SUFFICIENT VOLTAGE RATING

IN

C1: TAIYO YUDEN GMK212BJ105KG

C3: TAIYO YUDEN TMK316BJ106ML

L1: MURATA LQH32CN150K53

L2: MURATA LQH32CN100K53

LED Efﬁciency

= 3.6V, 3 LEDs

V

IN

80

75

70

65

60

55

50

45

0

5

10

LED CURRENT (mA)

20

15

3498 TA04b

3498f

20

LT3498

TYPICAL APPLICATIONS

Li-Ion to Four White LEDs and OLED/LCD Bias

V

= 3V TO 5V

C

C2

0.47µF

IN

4.7µF

L1

15µH

L2

10µH

16V

24mA

CAP1 SW1

V

SW2

CAP2 V

OUT2

C3

10µF

IN

C1

1µF

LT3498

R

SENSE1

FB2

LED1 CTRL1 GND1 GND2 CTRL2

OFF OFF

FB2

10Ω

2.21MΩ

ON

SHUTDOWN

AND

DIMMING

CONTROL

20mA

3498 TA05

C

, C2: X5R OR X7R WITH SUFFICIENT VOLTAGE RATING

IN

C1: TAIYO YUDEN GMK212BJ105KG

C3: TAIYO YUDEN TMK316BJ106ML

L1: MURATA LQH32CN150K53

L2: MURATA LQH32CN100K53

LED Efﬁciency

= 3.6V, 4 LEDs

V

IN

80

75

70

65

60

55

50

0

5

10

20

15

LED CURRENT (mA)

3498 TA05b

3498f

21

LT3498

TYPICAL APPLICATIONS

Li-Ion to Six White LEDs and OLED/LCD Bias

V

= 3V TO 5V

C

C2

0.47µF

IN

4.7µF

R

SENSE1

L1

15µH

L2

10µH

10Ω

D1

24V

24mA

CAP1 SW1

V

IN

SW2

CAP2 V

OUT2

C3

10µF

LT3498

C1

1µF

R

FB2

LED1 CTRL1 GND1 GND2 CTRL2

FB2

2.21MΩ

20mA

OFF

ON

SHUTDOWN AND

DIMMING CONTROL

SHUTDOWN AND

CONTROL

3498 TA06

C

IN

, C2: X5R OR X7R WITH SUFFICIENT VOLTAGE RATING

C1: TAIYO YUDEN GMK212BJ105KG

C3: TAIYO YUDEN TMK316BJ106ML

D1: CENTRAL SEMICONDUCTOR CMDSH-3

L1: MURATA LQH32CN150K53

L2: MURATA LQH32CN100K53

LED Efﬁciency,

IN

OLED Efﬁciency and Power Loss

V

= 3.6V, 6 LEDs

V

= 3.6V, V

= 16V

IN

OUT2

80

75

70

65

60

55

50

80

75

70

65

60

55

50

45

40

400

350

300

250

200

150

100

50

0

1

100

5

10

LED CURRENT (mA)

20

0.1

10

0

15

LOAD CURRENT (mA)

3498 TA06b

LOAD FROM V

OUT2

LOAD FROM CAP2

POWER LOSS FROM V

POWER LOSS FROM CAP2

OUT2

3498 TA06c

3498f

22

LT3498

PACKAGE DESCRIPTION

DDB Package

12-Lead Plastic DFN (3mm × 2mm)

(Reference LTC DWG # 05-08-1723 Rev Ø)

0.64 0.05

(2 SIDES)

0.70 0.05

2.55 0.05

1.15 0.05

PACKAGE

OUTLINE

0.25 0.05

0.45 BSC

2.39 0.05

(2 SIDES)

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED

R = 0.115

TYP

7

0.40 0.10

12

3.00 0.10

(2 SIDES)

R = 0.05

TYP

2.00 0.10

(2 SIDES)

PIN 1 BAR

TOP MARK

PIN 1

R = 0.20 OR

(SEE NOTE 6)

0.25 × 45°

0.64 0.10

(2 SIDES)

CHAMFER

6

1

(DDB12) DFN 0106 REV Ø

0.23 0.05

0.75 0.05

0.200 REF

0.45 BSC

2.39 0.10

(2 SIDES)

0 – 0.05

BOTTOM VIEW—EXPOSED PAD

NOTE:

1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE

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

3498f

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.

23

LT3498

TYPICAL APPLICATION

Output Voltage Ripple

vs Load Current

MAXIMUM OUTPUT

CURRENT AT 3V INPUT

(mA)

R

FB2

VALUE REQUIRED

V

(MΩ)

7

6

5

4

3

2

1

0

OUT

25

24

23

22

21

20

19

18

17

16

15

3.57

3.40

3.24

3.09

2.94

2.80

2.67

2.49

2.37

2.21

2.05

12.5

13.4

14.4

15.6

16.8

18.1

19.6

21.2

22.5

24.2

26

1

100

0.1

10

LOAD CURRENT (mA)

3498 TA06d

RELATED PARTS

PART

NUMBER

DESCRIPTION

COMMENTS

LT1932

Constant-Current, 1.2MHz, High Efﬁciency White LED

Boost Regulator

V

: 1V to 10V; V

= 34V; I = 1.2mA; I = <1µA; ThinSOT^TMPackage

OUT(MAX) Q SD

IN

LT1937

Constant-Current, 1.2MHz, High Efﬁciency White LED

Boost Regulator

V

: 2.5V to 10V; V

= 34V; I = 1.9µA; I = <1µA; ThinSOT and

Q SD

IN

OUT(MAX)

SC70 Packages

LT3463/

LT3463A

Dual Output, Boost/Inverter, 250mA I , Constant

V

: 2.3V to 15V; V

= 40V; I = 40µA; I = <1µA; 3mm × 3mm

Q SD

SW

IN

Off-Time, High Efﬁciency Step-Up DC/DC Converter with DFN-10 Package

Integrated Schottky Diodes

LT3465/

LT3465A

Constant-Current, 1.2/2.7MHz, High Efﬁciency White LED

Boost Regulator with Integrated Schottky Diode

V

: 2.3V to 16V; V

= 40V; I = 40µA; I = <1µA; 3mm × 3mm

Q SD

IN

OUT(MAX)

DFN-10 Package

LT3466/

LT3466-1

Dual Constant-Current, 2MHz, High Efﬁciency White LED

Boost Regulator with Integrated Schottky Diode

V

: 2.3V to 16V; V

= 40V; I = 65µA; I = <1µA; 3mm × 2mm

Q SD

IN

DFN-8 Package

LT3471

Dual Output, Boost/Inverter, 1.3A ISW, 1.2MHZ, High

Efﬁciency Boost-Inverting DC/DC Converter

V

: 2.4V to 16V; V

= 40V; I = 2.5µA; I = <1µA; 3mm × 3mm

Q SD

IN

DFN-10 Package

LT3473/

LT3473A

40V, 1A , 1.2MHz Micropower Low Noise Boost Converter V : 2.2V to 16V; V

with Output Disconnect

= 36V; I = 150µA; I = <1µA; 3mm × 3mm

Q SD

IN

DFN-12 Package

LT3491

Constant-Current, 2.3MHz, High Efﬁciency White LED

Boost Regulator with Integrated Schottky Diode

V

: 2.5V to 12V; V

= 27V; I = 12.6µA; I = <8µA; 2mm × 2mm

Q SD

IN

DFN-6 and SC70 Packages

LT3494/

LT3494A

40V, 180mA/350mA Micropower Low Noise Boost

Converter with Output Disconnect

V

: 2.3V to 16V; V

= 40V; I = 65µA; I = <1µA; 3mm × 2mm

Q SD

IN

OUT(MAX)

DFN-8 Package

LT3497

Dual 2.3MHz, Full Function LED Driver with Integrated

Schottky Diode and 250:1 True Color PWM^TMDimming

V

: 2.5V to 10V; V

= 32V; I = 6mA; I = <12µA; 3mm × 2mm

Q SD

IN

DFN-10 Package

LT3591

Constant-Current, 1MHz, High Efﬁciency White LED

Boost Regulator with Integrated Schottky Diode and 80:1 DFN-8 Package

True Color PWM Dimming

V

: 2.5V to 12V; V

= 40V; I = 4mA; I = <9µA; 3mm × 2mm

Q SD

IN

ThinSot and True Color PWM are trademarks of Linear Technology Corporation

3498f

LT 0507 • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

24

●

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


型号：	LT3466-1
厂家：	Linear
描述：	20mA LED Driver and OLED Driver with Integrated Schottky in 3mm x 2mm DFN 20毫安LED驱动器和OLED驱动器，集成肖特基二极管采用3mm x 2mm DFN封装驱动器肖特基二极管
文件：	总24页 (文件大小：450K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LT3466-1 [Linear]

相关型号：

SI9130DB

SI9135LG-T1

SI9135LG-T1-E3

SI9135_11

SI9136_11

SI9130CG-T1-E3

SI9130LG-T1-E3

SI9130_11

SI9137

SI9137DB

SI9137LG

SI9122E