LTC3440

1

3440fc

For more information www.linear.com/LTC3440

Description

Micropower Synchronous

Buck-Boost DC/DC Converter

Features

applications

n

Single Inductor

n

Fixed Frequency Operation with Battery Voltages

Above, Below or Equal to the Output

n

Synchronous Rectification: Up to 96% Efficiency

n

n

Up to 600mA Continuous Output Current

n

n

n

2.5V to 5.5V Input and Output Range

n

Programmable Oscillator Frequency

from 300kHz to 2MHz

n

Synchronizable Oscillator

n

Burst Mode Enable Control

n

<1µA Shutdown Current

n

Small Thermally Enhanced 10-Pin MSOP and

(3mm

× 3mm) DFN Packages

n

Palmtop Computers

n

Handheld Instruments

n

MP3 Players

n

Digital Cameras

The LTC®3440 is a high efficiency, fixed frequency, Buck-

Boost DC/DC converter that operates 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 prod-

uct ideal for single lithium-ion, multicell alkaline or NiMH

applications where the output voltage is within the battery

voltage range.

The device includes two 0.19Ω N-channel MOSFET

switches and two 0.22Ω P-channel switches. Switch-

ing frequencies up to 2MHz are programmed with an

external resistor and the oscillator can be synchronized

to an external clock. 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 has either a clock or is driven low, then

fixed frequency switching is enabled.

Other features include a 1µA shutdown, soft-start con-

trol, thermal shutdown and current limit. The LTC3440

is available in the 10-pin thermally enhanced MSOP and

(3mm

× 3mm) DFN packages.

SW1

SHDN/SS

MODE/SYNC

SW2

FB

GND

3

7

8

2

1

4

6

9

10

5

LTC3440

L1

10µH

R1

340k

R2

200k

R3

15k

3440 TA01

60.4k

C1: TAIYO YUDEN JMK212BJ106MG

C2: TAIYO YUDEN JMK325BJ226MM

L1: SUMIDA CDRH6D38-100

*1 = Burst Mode OPERATION

0 = FIXED FREQUENCY

C1

10µF

Li-Ion

*

+

C5 1.5nF

C2

22µF

3.3V

600mA

2.5

3.0

3.5

4.0

4.5

3440 TA02

5.0

100

98

96

94

92

90

88

86

84

82

80

5.5

tYpical application

Li-Ion to 3.3V at 600mA Buck-Boost Converter

L

, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered

trademarks and ThinSOT is a trademark of Linear Technology Corporation. All other

trademarks are the property of their respective owners.