LINEAR TECHNOLOGY LTC3441 Technical data

FEATURES

■

Regulated Output with Input Above, Below or Equal
to the Output

■

Single Inductor, No Schottky Diodes

■

High Efficiency: Up to 95%

■

25µA Quiescent Current in Burst Mode® Operation

■

Up to 1.2A Continuous Output Current from a Single
Lithium-Ion

■

True Output Disconnect in Shutdown

■

2.4V to 5.5V Input Range

■

2.4V to 5.25V Output Range

■

1MHz Fixed Frequency Operation

■

Synchronizable Oscillator

■

Selectable Burst Mode or Fixed Frequency Operation

■

<1µA Quiescent Current in Shutdown

■

Small, Thermally Enhanced 12-Lead (4mm × 3mm)
DFN package

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APPLICATIO S

■

Handheld Computers

■

Handheld Instruments

■

MP3 Players

■

Digital Cameras

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

Burst Mode is a registered trademark of Linear Technology Corporation.

LTC3441

High Current Micropower

Synchronous Buck-Boost

DC/DC Converter

U

DESCRIPTIO

The LTC®3441 is a high efficiency, fixed frequency, buck­boost DC/DC converter that operates efficiently from input
voltages above, below or equal to the output voltage. The
topology incorporated in the IC provides a continuous trans­fer function through all operating modes, making the prod­uct ideal for single lithium ion or multicell applications where
the output voltage is within the battery voltage range.

The device includes two 0.10Ω N-channel MOSFET
switches and two 0.11Ω P-channel switches. External
Schottky diodes are optional, and can be used for a
moderate efficiency improvement. The operating frequency
is internally set to 1MHz and can be synchronized up to

1.7MHz. Quiescent current is only 25µA in Burst Mode
operation, maximizing battery life in portable applications.
Burst Mode operation is user controlled and can be
enabled by driving the MODE/SYNC pin high. If the MODE/
SYNC pin is driven low or with a clock, then fixed fre­quency switching is enabled.

Other features include a 1µA shutdown, soft-start control,
thermal shutdown and current limit. The LTC3441 is
available in a thermally enhanced 12-lead (4mm × 3mm)
DFN package.

TYPICAL APPLICATIO

Li-Ion to 3.3V at 1A Buck-Boost Converter

L1

4.7µH

4

2.5V TO 4.2V

Li-Ion

*1 = Burst Mode OPERATION
0 = FIXED FREQUENCY

C

IN

10µF

*

SW1

9

PV

10

V

1

SHDN/SS

7

MODE/SYNC

3

PGND

IN

IN

SW2

V

OUT

LTC3441

FB

V

C

GND

PGND

: TAIYO YUDEN JMK212BJ106MG

C

IN

: TAIYO YUDEN JMK325BJ226MM

C

OUT

L1: TOKO A916CY-4R7M

U

Efficiency vs V

100

V

= 3.3V

OUT

V

OUT

3.3V

5

8

12

15k

11

2

6

1.5nF

340k

200k

1A

C

OUT

22µF

3441 TA01

95

90

85

80

75

70

EFFICIENCY (%)

65

60

55

50

2.5

I

= 1A

OUT

3

3.5
VIN (V)

I

= 200mA

OUT

4 4.5

IN

5.5

5

3441 TA02

sn3441 3441fs

1

LTC3441

PACKAGE/ORDER I FOR ATIO

UU

W

WWWU

ABSOLUTE AXI U RATI GS

(Note 1)

VIN, V
SW1, SW2 Voltage

DC ........................................................... – 0.3V to 6V

Pulsed < 100ns ...................................... –0.3V to 7V

SHDN/SS, MODE/SYNC Voltage ................. –0.3V to 6V

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

Maximum Junction Temperature (Note 4) ........... 125°C

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

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

OUT

TOP VIEW

13

= 125°C

12

FB

11

V

V

10

PV

9

V

8

MODE/SYNC

7

C

IN

IN

OUT

SHDN/SS

Consult LTC Marketing for parts specified with wider operating temperature ranges.

1

GND

2

PGND

3

SW1

4

SW2

5

PGND

6

12-LEAD (4mm × 3mm) PLASTIC DFN

DE12 PACKAGE

T

JMAX

= 53°C/W 1-LAYER BOARD

θ

JA

θ

= 43°C/W 4-LAYER BOARD

JA

= 4.3°C/W

θ

JC

EXPOSED PAD IS PGND (PIN 13)

MUST BE SOLDERED TO PCB

ORDER PART

NUMBER

LTC3441EDE

DE PART MARKING

3441

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at TA = 25°C. VIN = V

PARAMETER CONDITIONS MIN TYP MAX UNITS

Input Start-Up Voltage ● 2.3 2.4 V

Output Voltage Adjust Range ● 2.4 5.25 V

Feedback Voltage ● 1.19 1.22 1.25 V

Feedback Input Current VFB = 1.22V 1 50 nA

Quiescent Current—Burst Mode Operation VC = 0V, MODE/SYNC = 3V (Note 3) 25 40 µA

Quiescent Current—SHDN V

Quiescent Current—Active MODE/SYNC = 0V (Note 3) 520 900 µA

NMOS Switch Leakage Switches B and C 0.1 7 µA

PMOS Switch Leakage Switches A and D 0.1 10 µA

NMOS Switch On Resistance Switches B and C 0.10 Ω

PMOS Switch On Resistance Switches A and D 0.11 Ω

Input Current Limit ● 2 3.2 A

Max Duty Cycle Boost (% Switch C On) ● 70 88 %

Min Duty Cycle ● 0%

Frequency Accuracy ● 0.85 1 1.15 MHz

MODE/SYNC Threshold ● 0.4 1.4 V

MODE/SYNC Input Current V

Error Amp AV

Error Amp Source Current 14 µA

Error Amp Sink Current 300 µA

SHDN/SS Threshold When IC is Enabled ● 0.4 1 1.4 V

SHDN/SS Threshold When EA is at Max Boost Duty Cycle 2 2.4 V

SHDN/SS Input Current V

OL

= SHDN = 0V, Not Including Switch Leakage 0.1 1 µA

OUT

Buck (% Switch A In)

MODE/SYNC

SHDN

= 5.5V 0.01 1 µA

= 5.5V 0.01 1 µA

The ● denotes the specifications which apply over the full operating

= 3.6V,unless otherwise noted.

OUT

● 100 %

90 dB

sn3441 3441fs

2

ELECTRICAL CHARACTERISTICS

LTC3441

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

Note 2: The LTC3441E is guaranteed to meet performance 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

Note 4: This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may result in device degradation or failure.

with statistical process controls.
Note 3: Current measurements are preformed when the outputs are not

switching.

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Efficiency

100

90

Burst Mode

OPERATION

80

70

60

50

VIN = 2.7V

40

EFFICIENCY (%)

30

20

10

V

= 3.3V

OUT

0

0.1 10 100 1000

1

I

OUT

VIN = 4.2V

VIN = 3.6V

(mA)

3441 G17

10mV/DIV

AC-COUPLED

V

Ripple at 1A Load

OUT

V

OUT

L = 4.7µH1µs/DIV
C

= 47µF

OUT

I

= 1A

OUT

= 3.3V

V

OUT

3441 G02

BUCK
VIN = 4.2V

BUCK-BOOST
V

= 3.3V

IN

BOOST
V

= 2.7V

IN

V

OUT

100mV/DIV

1A

100mA

Load Transient Response,
100mA to 1A

100µs/DIV

3441 G01

Switch Pins in Buck-Boost Mode

SW1

2V/DIV

SW2

2V/DIV

V

= 3.3V 50ns/DIV 3441 G03

IN

V

= 3.3V

OUT

I

= 500mA

OUT

Switch Pins Entering
Buck-Boost Mode

SW1

2V/DIV

SW2

2V/DIV

V

= 4.2V 50ns/DIV 3441 G04

IN

V

= 3.3V

OUT

I

= 500mA

OUT

sn3441 3441fs

3

LTC3441

TEMPERATURE (°C)

–55

2.8

CURRENT LIMIT (A)

3.0

3.2

3.4

–25 5 35 65

3441 G13

95

125

VIN = V

OUT

= 3.6V

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Switch Pins Before Entering

Active Quiescent Current

630

CURRENT (µA)

OUT

+ V

IN

V

620

610

600

590

580

570

560

550

540

530

520

VIN = V

–55

= 3.6V

OUT

–25 5 35 65

TEMPERATURE (°C)

95 125

SW1

2V/DIV

SW2

2V/DIV

Boost Mode

= 3V 50ns/DIV 3441 G05

V

IN

V

= 3.3V

OUT

= 500mA

I

OUT

3441 G06

Feedback Voltage

1.241
VIN = V

= 3.6V

–55

OUT

–25

TEMPERATURE (°C)

1.236

1.231

1.226

1.221

1.216

1.211

FEEDBACK VOLTAGE (V)

1.206

1.201

1.196

5

35 125

65

95

3441 G07

Burst Mode Quiescent Current

50

CURRENT (µA)

OUT

+ V

IN

V

VIN = V

40

30

20

10

–55

= 3.6V

OUT

–25 5 35 65

TEMPERATURE (°C)

Error Amp Sink Current

400

VIN = V

350

300

OUT

= 3.6V

95 125

3441 G08

Feedback Voltage Line Regulation Error Amp Source Current

90

VIN = V

80

70

LINE REGULATION (dB)

60

–55

= 2.4V TO 5.5V

OUT

–25 5 35 65

TEMPERATURE (°C)

125

95

3441 G09

20

VIN = V

= 3.6V

OUT

15

10

EA SOURCE CURRENT (µA)

5

–55

–25 5 35 65

TEMPERATURE (°C)

Output Frequency Current Limit

1.2
VIN = V

1.1

1.0

OUT

= 3.6V

125

95

3441 G10

EA SINK CURRENT (µA)

250

200

4

–55

–25 5 35 65

TEMPERATURE (°C)

95 125

3441 G11

FREQUENCY (MHz)

0.9

0.8
–55

–25 5 35 65

TEMPERATURE (°C)

95 125

3441 G12

sn3441 3441fs

UW

TEMPERATURE (°C)

–55

2.10

MINIMUM START VOLTAGE (V)

2.15

2.20

2.25

2.30

–25 5 35 65

3441 G16

95 125

TYPICAL PERFOR A CE CHARACTERISTICS

LTC3441

NMOS R

0.15
VIN = V
SWITCHES B AND C

0.13

(Ω)

0.11

DS(ON)

0.09

NMOS R

0.07

0.05

–55

U

DS(ON)

= 3.6V

OUT

53565

–25

TEMPERATURE (°C)

95 125

3441 G14

UU

0.15

0.14

0.13

0.12

(Ω)

0.11

0.10

DS(ON)

0.09

PMOS R

0.08

0.07

0.06

0.05

PMOS R

–50

DS(ON)

VIN = V
SWITCHES A AND D

= 3.6V

OUT

–25

5

TEMPERATURE (°C)

PI FU CTIO S

SHDN/SS (Pin 1): Combined Soft-Start and Shutdown.
Applied voltage < 0.4V shuts down the IC. Tie to >1.4V to
enable the IC and >2.4V to ensure the error amp is not
clamped from soft-start. An RC from the shutdown com­mand signal to this pin will provide a soft-start function by
limiting the rise time of the VC pin.

GND (Pin 2): Signal Ground for the IC.

PGND (Pins 3, 6, 13 Exposed Pad): Power Ground for the

Internal NMOS Power Switches

Minimum Start Voltage

35 65

125

95

3441 G15

light loads. The Burst Mode operation will continue until
the pin is driven low.

MODE/SYNC = Low: Disable Burst Mode operation and
maintain low noise, constant frequency operation .

MODE/SYNC = External CLK : Synchronization of the
internal oscillator and Burst Mode operation disable. A
clock pulse width between 100ns and 2µs and a clock
frequency between 2.3MHz and 3.4MHz (twice the
desired frequency) is required to synchronize the IC.

SW1 (Pin 4): Switch pin where the internal switches A and
B are connected. Connect inductor from SW1 to SW2. An
optional Schottky diode can be connected from this SW1
to ground. Minimize trace length to keep EMI down.

SW2 (Pin 5): Switch pin where the internal switches C
and D are connected. An optional Schottky diode can be
connected from SW2 to V
V

> 4.3V). Minimize trace length to keep EMI down.

OUT

MODE/SYNC (Pin 7): Burst Mode Select and Oscillator
Synchronization.

MODE/SYNC = High: Enable Burst Mode Operation.
During the period where the IC is supplying energy to
the output, the inductor peak inductor current will reach

0.8A and return to zero current on each cycle. In Burst
Mode operation the operation is variable frequency,
which provides a significant efficiency improvement at

(it is required where

OUT

f

= f

OSC

V

(Pin 8): Output of the Synchronous Rectifier. A filter

OUT

capacitor is placed from V
capacitor is recommended as close to the V

SYNC

/2

to GND. A ceramic bypass

OUT

and GND

OUT

pins as possible.

PVIN (Pin 9): Power VIN Supply Pin. A 10µF ceramic capaci-
tor is recommended as close to the PVIN and PGND pins
as possible

VIN (Pin 10): Input Supply Pin. Internal VCC for the IC.

VC (Pin 11): Error Amp Output. A frequency compensation

network is connected from this pin to the FB pin to
compensate the loop. See the section “Compensating the
Feedback Loop” for guidelines.

FB (Pin 12): Feedback Pin. Connect resistor divider tap
here. The output voltage can be adjusted from 2.4V to

5.25V. The feedback reference voltage is typically 1.22V.

sn3441 3441fs

5