LINEAR TECHNOLOGY LTC3454 Technical data

FEATURES

LTC3454

1A Synchronous Buck-Boost

High Current LED Driver

U

DESCRIPTIO

■

High Effi ciency: >90% Typical in Torch Mode,

>80% in Flash Mode

■

Wide VIN Range: 2.7V to 5.5V

■

Up to 1A Continuous Output Current

■

3.5% LED Current Programming Accuracy

■

Internal Soft-Start

■

Open/Shorted LED Protection

■

Constant Frequency 1MHz Operation

■

Zero Shutdown Current

■

Overtemperature Protection

■

Small Thermally Enhanced 10-Lead (3mm × 3mm)

DFN Package

U

APPLICATIO S

■

Cell Phone Camera Flash

■

Cell Phone Torch Lighting

■

Digital Cameras

■

PDAs

■

Misc Li-Ion LED Drivers

The LTC®3454 is a synchronous buck-boost DC/DC
converter optimized for driving a single high power LED
at currents up to 1A from a single cell Li-Ion battery in­put. The regulator operates in either synchronous buck,
synchronous boost, or buck-boost mode depending on
input voltage and LED forward voltage. P

LED/PIN

effi ciency
greater than 90% can be achieved over the entire usable
range of a Li-Ion battery (2.7V to 4.2V).

LED current is programmable to one of four levels, includ­ing shutdown, with dual external resistors and dual enable
inputs. In shutdown no supply current is drawn.

A high constant operating frequency of 1MHz allows the
use of small external components. The LTC3454 is offered
in a low profi le (0.75mm) thermally enhanced 10-lead
(3mm × 3mm) DFN package.

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

All other trademarks are the property of their respective owners.

TYPICAL APPLICATIO

High Effi ciency Torch/Flash LED Driver

V

1-CELL

Li-Ion

2.7V-4.2V

0.1mF

IN

10mF

V

C

LED: LUMILEDS LXL-PWF1
L1: SUMIDA CDRH6D28-5RONC

V

IN

A

B

L1

5mH

SW1

1MHz

BUCK-BOOST

GND (EXPOSED PAD)

U

SW2 V

D

C

OUT

LTC3454

LED

I

SET1

I

SET2

10mF

LED

EN1 (TORCH)

EN2 (FLASH)

R

ISET2

3.65k
1%

I

LED

EN2 EN1 I

0 0 0 (SHUTDOWN)
0 1 150mA
1 0 850mA
111A

R

ISET1

20.5k
1%

3453 TA01a

LED

LED Power Effi ciency vs V

100

I

= 150mA

95

90

85

80

75

EFFICIENCY (%)

70

TA = 25°C

65

EFFICIENCY = (V

60

2.7

LED

I

LED

OUT

3.1 3.93.5 4.7

= 1A

– V

LED)ILED/VINIIN

4.3

(V)

V

IN

IN

5.55.1

3454 TA01b

3454f

1

LTC3454

WW

W

ABSOLUTE AXI U RATI GS

(Note 1)

VIN, SW1, SW2, V

, EN1, EN2, I

V

C

Voltage .............................– 0.3V to (V

LED Peak Current ...................................................1.25A

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

Operating Temperature Range (Note 2) ...–40°C to 85°C

Junction Temperature (Note 3) ............................. 125°C

Voltage ......................–0.3V to 6V

OUT

, I

SET2

SET1

U

+ 0.3V) or 6V

IN

UUW

PACKAGE/ORDER I FOR ATIO

TOP VIEW

10

EN1

1

EN2

2

3

I

SET1

4

I

SET2

5

LED

10-LEAD (3mm × 3mm) PLASTIC DFN

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

DD PACKAGE

T

= 125°C, θJA = 40°C/W

JMAX

SW1

V

9

IN

V

811

C

7

V

OUT

6

SW2

ORDER PART NUMBER DD PART MARKING

LTC3454EDD

Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/

Consult LTC Marketing for parts specifi ed with wider operating temperature ranges.

●

The

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifi cations are at T

= 25°C, VIN = 3.6V, R

A

PARAMETER CONDITIONS MIN TYP MAX UNITS

Input Supply Voltage (V

)

IN

Input DC Supply Current (Typicals at V
Normal Operation 2.7V ≤ V
Shutdown 2.7V ≤ V
UVLO V

Undervoltage Lockout Threshold V
VIN Falling 1.75 1.90 V

V

, V

EN1

V

EN1

V

EN1

I

SET1

788 800 812 mV

DC Threshold for Normal Operation (VIH)

EN2

, V

DC Threshold for Shutdown (VIL)

EN2

, V

Input Current

EN2

and I

Servo Voltage 3.08k ≤ R

SET2

LED Output Current to Programming Current Ratio I
3775 3850 3925 mA/mA

LED Pin Voltage I
Regulated Maximum V
PMOS Switch R
NMOS Switch R

ON

ON

LED Pin Open, Programmed I

OUT

Switches A and D (V
Switches B and C 130 mΩ

< UVLO Threshold; V

IN

Rising

IN

/(I

LED

ISET1

= 1A 105 mV

LED

Forward Current Limit Switch A 2.5 3.4 A
Reverse Current Limit Switch D (V
PMOS Switch Leakage Switches A, D –1 1 µA
NMOS Switch Leakage Switches B, C –1 1 µA
Oscillator Frequency 0.9 1.0 1.15 MHz
Soft-Start Time 200 µs

Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.

Note 2: The LTC3454 is guaranteed to meet specifi cations from 0°C to
70°C. Specifi cations over the –40°C to 85°C operating temperature range
are assured by design, characterization and correlation with statistical
process controls.

denotes the specifi cations which apply over the full operating

= 20.5k unless otherwise noted. (Note 2)

ISET

●

2.7 5.5 V

= 3.6V, R

IN

≤ 5.5V (Note 4)

IN

≤ 5.5V; V

IN

ISET1

EN1

||R

ISET2

+ I

), I

ISET2

OUT

= 3.6V) 275 mA

OUT

= R

ISET1

= V

EN2

= V

EN1

≤ 20.5k

= 500mA (Note 5)

LED

LED

= 20.5k)

ISET2

= 0V 0 1 µA

= VIN 5 10 µA

EN2

●

2.05 2.3 V

●

0.68 1.2 V

●

0.2 0.66 V

●

–1 1 µA

●

780 800 812 mV

●

3725 3850 3975 mA/mA

= 1A

●

4.95 5.15 5.35 V

= 3.6V) 170 mΩ

Note 3: T

is calculated from the ambient temperature TA and power

J

dissipation PD according to the following formula:
T

= TA + (PD • θJA °C/W).

J

Note 4: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency.

Note 5: This parameter is tested using a feedback loop which servos V
to 1.8V.

LBQX

825 1200 µA

C

3454f

2

UW

TYPICAL PERFOR A CE CHARACTERISTICS

LTC3454

Undervoltage Lockout Threshold
vs Temperature

2.4

2.3

2.2

2.1

2.0

1.9

1.8

1.7

UVLO THRESHOLD (V)

1.6

1.5

1.4
–35 5

–15

–55

I

Servo Voltage

SET1,2

VIN RISING

VIN FALLING

45 125

65

25

TEMPERATURE (°C)

vs Temperature

812

VIN = 3.6V

= 15k

R

ISET1,2

808

804

(mV)

800

ISET1,2

V

796

Enable Thresholds
vs Temperature

1200

VIN = 3.6V

1100

1000

900

800

700

600

500

ENABLE THRESHOLDS (mV)

400

300

85

105

3454 G01

200

812

808

804

(mV)

800

ISET1,2

V

796

–35 5

–15

–55

I

Servo Voltage vs V

SET1,2

TA = 25°C

= R

R

ISET1

ISET2

45 125

25

TEMPERATURE (°C)

= 15k

V

IH

V

IL

85

105

65

3454 G02

IN

Enable Thresholds vs V

1200

TA = 25°C

1100

1000

900

800

700

600

500

ENABLE THRESHOLDS (mV)

400

300

200

3.1 3.9

3.5 5.5

Servo Voltage vs R

VIN = 3.6V

= 25°C

T

A

812

808

804

(mV)

800

ISET1,2

V

796

2.7

I

SET1,2

VIN (V)

4.3

IN

V

IH

V

IL

4.7

5.1

3454 G03

ISET

792

788

–35 5

–55

–15

TEMPERATURE (°C)

45 125

25

LED Current Programming Ratio
vs Temperature

4050

VIN = 3.6V

4000

3950

3900

3850

RATIO

3800

3750

3700

3650

–35 125

–55

PROGRAMMED I
PROGRAMMED I
PROGRAMMED I

–15

25

5

TEMPERATURE (°C)

45

65

65

85

LED
LED
LED

85

105

3454 G04

= 1A
= 500mA
= 150mA

105

3454 G07

792

788

2.7

3.1 3.5

4.3 5.1 5.5

3.9 4.7
VIN (V)

LED Current Programming Ratio
vs V

IN

4050

4000

3950

3900

3850

RATIO

3800

3750

3700

3650

PROGRAMMED I

= 25°C

T

A

3.1 5.5

2.7

LED

3.9 4.7

3.5

= 500mA

4.3

VIN (V)

3454 G05

5.1

3454 G08

792

788

150

120

(mV)

LED

V

3

711

vs Temperature

V

LED

VIN = 3.6V

90

60

30

0

–55

–35 –15

19 27 31

15 23

R

(kΩ)

ISET

PROGRAMMED

= 1A

I

LED

PROGRAMMED

= 500mA

I

LED

PROGRAMMED

= 100mA

I

LED

25

5 45 125

TEMPERATURE (°C)

3454 G06

65 85 105

3454 G09

3454f

3

LTC3454

UW

TYPICAL PERFOR A CE CHARACTERISTICS

V

vs V

60

58

56

54

52

(mV)

50

LED

V

48

46

44

42

40

2.7

LED

PROGRAMMED I
T

= 25°C

A

3.1

3.5

IN

= 500mA

LED

4.3

3.9
VIN (V)

Maximum Regulated V
vs Programmed LED Current

5.40
VIN = 3.6V

5.35

= 25°C

T

A

5.30

5.25

5.20

(V)

5.15

OUT

V

5.10

5.05

5.00

4.95

4.90

200 1000

100

300

500

600

400

PROGRAMMED I

LED

700

4.7

OUT

(mA)

800

5.1

3454 G10

5.5

Maximum Regulated V
vs Temperature

5.40
PROGRAMMED I

5.35

= 3.6V

V

IN

5.30

5.25

5.20

(V)

5.15

OUT

V

5.10

5.05

5.00

4.95

4.90
–35 125

–55

–15

= 1A

LED

25

5

TEMPERATURE (°C)

OUT

45

105

65

85

Maximum Regulated V
vs V

IN

5.40
PROGRAMMED I

5.35

= 25°C

T

A

5.30

5.25

5.20

(V)

5.15

OUT

V

5.10

5.05

5.00

4.95

4.90

2.7

3.1

3.5

LED

3.9

= 1A

4.3

VIN (V)

OUT

4.7

5.1

5.5

3454 G12

900

3454 G13

PMOS R

300

MEASURED AT 500mA

270

240

210

(mΩ)

DS

180

R

150

120

90

–35 –15 5 25 45 125

–55

vs Temperature

DS(ON)

VIN = 2.7V

VIN = 3.6V

VIN = 4.2V

TEMPERATURE (°C)

VIN = 5.5V

65 85 105

3454 G14

NMOS R

200

MEASURED AT 500mA

180

160

140

120

(mΩ)

DS

R

100

80

60

40

VIN = 3.6V

–35 –15 5 25 45 125

–55

vs Temperature

DS(ON)

VIN = 2.7V

VIN = 4.2V

TEMPERATURE (°C)

VIN = 5.5V

65 85 105

3454 G15

4

Oscillator Frequency
vs Temperature

1100

V

= 3V

OUT

1080

1060

1040

1020

1000

980

FREQUENCY (kHz)

960

940

920

900

–55

–35 5

–15

VIN = 4.2V

VIN = 3.6V

TEMPERATURE (°C)

VIN = 5.5V

VIN = 2.7V

45 125

25

85

65

105

3454 G16

LED Power Effi ciency
vs LED Current

100

95

90

85

80

75

EFFICIENCY (%)

70

VIN = 3.6V

= 25°C

T

A

65

EFFICIENCY = (V
FRONT PAGE APPLICATION

60

200 1000

100

300

400

OUT

500

I

– V

LED

LED)ILED/VINIIN

600

(mA)

700

800

900

3454 G17

3454f