LINEAR TECHNOLOGY LTC3453 Technical data

FEATURES

LTC3453

Synchronous Buck-Boost

High Power White LED Driver

U

DESCRIPTIO

■

High Efficiency: 90% Typical Over Entire
Li-Ion Battery Range

■

Wide VIN Range: 2.7V to 5.5V

■

Up to 500mA Continuous Output Current

■

Internal Soft-Start

■

Open/Shorted LED Protection

■

LED Current Matching Typically <2%

■

Constant Frequency 1MHz Operation

■

Low Shutdown Current: 6µA

■

Overtemperature Protection

■

Small Thermally Enhanced 16-Lead (4mm x 4mm)
QFN Package

U

APPLICATIO S

■

Cell Phones

■

Digital Cameras

■

PDAs

■

Portable Devices

, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.

The LTC®3453 is a synchronous buck-boost DC/DC con­verter optimized for driving up to 4 white LEDs at a
combined current of up to 500mA from a single Li-Ion
battery input. The regulator operates in either synchro­nous buck, synchronous boost, or buck-boost mode,
depending on input voltage and LED maximum forward
voltage. Optimum efficiency is achieved using a propri­etary architecture that determines which LED requires the
largest forward voltage drop at its programmed current,
and regulates the common output rail for lowest dropout.
Efficiency of 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 current setting resistors and dual
enable pins. In shutdown, the supply current is only 6µA.

A high constant operating frequency of 1MHz allows the
use of a small external inductor. The LTC3453 is offered
in a low profile (0.75mm) thermally enhanced 16-lead
(4mm x 4mm) QFN package.

TYPICAL APPLICATIO

High Efficiency Torch/Flash LED Driver

V

IN

1-CELL

2.7V to 4.2V

0.1µF

Li-Ion

8.25k

2.2µF

EN1 (TORCH)

EN2 (FLASH)

1%

3.48k
1%

I

I

SET1

SET2

EN1

EN2

V

PV

IN

IN

V

C

U

L1

4.7µH

SW1 SW2 V

1MHz

BUCK-BOOST

GND PGNDGND

OUT

LTC3453

3453 TA01a

150mA/500mA

LED1

LED2

LED3

LED4

D1: LUMILEDS LXCL-PWF1
L1: VISHAY DALE IDCS-2512

EN1 EN2

0

0

1

0

0

1

1

1

D1

I

LED

0 (SHUTDOWN)
150mA
350mA
500mA

4.7µF

Torch Mode Efficiency vs V

100

(%)

IN

90

/P

LED

80

70

60

LED POWER EFFICIENCY P

I

= 150mA

LED

= 25°C

T

A

50

3.1 3.5 3.9 5.54.3 5.1

2.7
VIN (V)

EFFICIENCY

I

IN

4.7

IN

3453 TA01b

180

160

INPUT CURRENT (mA)

140

120

100

80

3453fa

1

LTC3453

16 15 14 13

5 6 7 8

UF PACKAGE

16-LEAD (4mm × 4mm) PLASTIC QFN

9

10

11

17

12

4

3

2

1

TOP VIEW

V

IN

EN1

I

SET1

LED1

V

C

EN2

I

SET2

LED4

PVINSW1

SW2

V

OUT

GND

LED2

LED3

GND

WW

W

U

ABSOLUTE AXI U RATI GS

(Note 1)

VIN, PVIN, SW1, SW2, V

LED1 to LED4 Voltage ...... –0.3V to (V

, EN1, EN2,

V

C

I

, I

SET1

Voltage .......... –0.3V to (VIN + 0.3V) or 6V

SET2

LED1 to LED4 Peak Current ................................ 250mA

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

+ 0.3V) or 6V

OUT

UUW

PACKAGE/ORDER I FOR ATIO

T

= 125°C, θJA = 40°C/W, θJC = 2.6°C/W

JMAX

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

ORDER PART NUMBER

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.

UF PART MARKING

3453LTC3453EUF

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at T

PARAMETER CONDITIONS MIN TYP MAX UNITS

Input Supply Voltage

Input DC Supply Current

Normal Operation 2.7V ≤ V
Shutdown 2.7V ≤ V
UVLO V

Undervoltage Lockout Threshold VIN Rising

EN1,2 DC Threshold for Normal Operation 2.7V ≤ VIN ≤ 5.5V, V

EN1,2 DC Threshold for Shutdown (I

EN1,2 Input Current V

I

Servo Voltage R

SET1,2

LED Output Current Ratio I

LED Output Current Matching (MAX – MIN)/[(MAX + MIN)/2] • 100%, I

LED Pin Drain Voltage I

Regulated Maximum V

PMOS Switch R

NMOS Switch R

Forward Current Limit Switch A 1125 1612 2100 mA

Reverse Current Limit Switch D 200 mA

ON

ON

OUT

LEDx

IN

V

IN

= 0) 2.7V ≤ VIN ≤ 5.5V, V

EN1,2

ISET1,2

R

ISET1,2

LED

2.7V ≤ V

V

LEDx

LEDx

V

LEDx

Switches A and D, @ 100mA 0.3 Ω

Switches B and C, @ 100mA 0.25 Ω

≤ 5.5V, R

IN

≤ 5.5V; V

IN

< UVLO Threshold 3 5 µA

Falling 1.6 1.9 V

= 3.6V

= 4.12k, 0°C ≤ TA ≤ 85°C 788 800 812 mV
= 4.12k, –40°C ≤ TA ≤ 85°C

/(I

+ I

SET1

≤ 5.5V

IN

= 300mV

= 75mA 130 mV

= 0V

The ● denotes the specifications which apply over the full operating

= 25°C, VIN = V

A

||R

ISET1

= V

EN1

Rising

EN1,2

Falling

EN1,2

), I

SET2

= 75mA, V

LEDx

= 3.6V unless otherwise noted. (Note 2)

OUT

●

2.7 5.5 V

= 51.1k, I

ISET2

= 0V 6 18 µA

EN2

LEDx

= 0 (Note 4) 0.6 1 mA

LEDx

●

●

●

0.2 0.63 V

●

–1 1 µA

●

780 800 812 mV

= 300mV, 365 384 403 mA/mA

●

357 384 403 mA/mA

= 75mA 2 6 %

LEDx

●

4.4 4.5 4.6 V

2 2.3 V

0.65 1 V

3453fa

2

LTC3453

TEMPERATURE (°C)

–55

FREQUENCY (kHz)

1050

1040

1030

1020

950

1010

1000

990

980

970

960

45 65 85 10525

3453 G07

–35 –15 5 125

VIN = 5.5V

V

OUT

= 3V

VIN = 4.2V

VIN = 3.6V

VIN = 2.7V

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at T

PARAMETER CONDITIONS MIN TYP MAX UNITS

PMOS Switch Leakage Switches A and D

NMOS Switch Leakage Switches B and C

Oscillator Frequency 0.9 1 1.1 MHz

Soft-Start Time 0.65 ms

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 LTC3453E is guaranteed to meet specifications from 0°C to
70°C. Specifications over the –40°C to 85°C operating temperature range
are assured by design, characterization and correlation with statistical
process controls.

TYPICAL PERFOR A CE CHARACTERISTICS

Input DC Supply Current in
Shutdown vs Temperature

20

FRONT PAGE APPLICATION

18

16

14

12

10

(µA)

IN

I

8

6

4

2

0

–35 –15 5 125

–55

I

SET1,2

812

TA = 25°C
R

ISET1,2

808

804

(mV)

800

ISET1,2

V

796

792

788

2.7

Servo Voltage vs V

3.1 5.5

VIN = 5.5V

TEMPERATURE (°C)

= 8.25k

3.9 4.3 4.7 5.13.5
VIN (V)

VIN = 4.2V

45 65 85 10525

VIN = 3.6V

VIN = 2.7V

IN

UW

3453 G01

3453 G05

The ● denotes the specifications which apply over the full operating

= 25°C, VIN = V

A

= 3.6V unless otherwise noted. (Note 2)

OUT

Note 3: T

dissipation P
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.

Undervoltage Lockout Threshold
vs Temperature

2.2

2.1

VIN RISING

2.0

1.9

UVLO THRESHOLD (V)

1.8

1.7
–55

VIN FALLING

–35 –15 5 125

TEMPERATURE (°C)

45 65 85 10525

Regulated Maximum V
Temperature

4.55
VIN = 3.6V

ALL LED PINS OPEN

4.54

4.53

4.52

4.51

(V)

4.50

OUT

V

4.49

4.48

4.47

4.46

4.45

–35 –15 5 125

–55

TEMPERATURE (°C)

45 65 85 10525

●

●

is calculated from the ambient temperature TA and power

J

according to the following formula:

D

I

Servo Voltage vs

SET1,2

Temperature

812

VIN = 3.6V

= 8.25k

R

ISET1,2

808

804

(mV)

800

ISET1,2

V

796

792

OUT

vs

3453 G02

788

–35 –15 5 125

–55

TEMPERATURE (°C)

Oscillator Frequency vs

45 65 85 10525

Temperature

3453 G06

1 µA

1 µA

3453 G04

3453fa

3

LTC3453

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Efficiency vs LED Current Output Voltage Ripple Startup Transient

100

90

FRONT PAGE APPLICATION

, VIN = 3.6V, TA = 25°C

P

LED/PIN

CH1, V

2V/DIV

OUT

80

70

EFFICIENCY (%)

60

50

150 200 250 500

100

LED CURRENT (mA)

350 400 450300

3453 G07

20mV/DIV

AC COUPLED

FRONT PAGE APPLICATION

= 3.6V

V

IN

= 150mA

I

LED

UUU

PI FU CTIO S

VIN (Pin 1): Signal Voltage Input Supply Pin [2.7V ≤ VIN ≤

5.5V]. Recommended bypass capacitor to GND is 2.2µF
ceramic or larger. Connect to PV

EN1 (Pin 2): Enable Input Pin for I

I

(Pin 3): White Led Current Programming Pin. A

SET1

resistor to ground programs each current source output to
I

= 384(0.8V/R

LED

any amount set by EN2/I

). This amount of current adds to

ISET1

SET2

LED1 to LED4 (Pins 4, 6, 7, 9): Individual Low Dropout
Current Source Outputs for White LED Current Biasing.
Connect each white LED between V
LEDx pin. Unused LEDx outputs should be connected to

.

V

OUT

GND (Pins 5 and 8): Signal Ground Pin. Connect to PGND
(Exposed Pad).

I

(Pin 10): White Led Current Programming Pin. A

SET2

resistor to ground programs each current source output to
I

= 384(0.8V/R

LED

any amount set by EN1/I

). This amount of current adds to

ISET2

SET1

(Pin 16).

IN

Current.

SET1

if also used.

and an individual

OUT

if also used.

0V

CH2, EN1

1V/DIV

0V

5µs/DIV

3453 G08

FRONT PAGE APPLICATION

= 3.6V

V

IN

= 150mA

I

LED

EN2 (Pin 11): Enable Input Pin for I

1ms/DIV

SET2

Current.

3453 G09

VC (Pin 12): Compensation Point for the Internal Error
Amplifier Output. Recommended compensation capacitor
to GND is 0.1µF ceramic or larger.

V

(Pin 13): Buck-Boost Output Pin. Recommended

OUT

bypass capacitor to GND is 4.7µF ceramic.

SW2 (Pin 14): Switching Node Pin. Connected to internal
power switches C and D. External inductor connects
between SW1 and SW2. Recommended value is 4.7µH.

SW1 (Pin 15): Switching Node Pin. Connected to internal
power switches A and B. External inductor connects
between SW1 and SW2. Recommended value is 4.7µH.

(Pin 16): Power Voltage Input Supply Pin. Connect to

PV

IN

V

(Pin 1).

IN

Exposed Pad (Pin 17): Power Ground Pin. Connect to
GND (Pin 8) and solder to PCB ground for optimum
thermal performance.

4

3453fa