LTC3421

1

3421f

s

Handheld Computers

s

Cordless Phones

s

GPS Receivers

s

Battery Backup Supplies

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

s

Synchronous Rectification: Up to 96% Efficiency

s

True Output Disconnect

s

Inrush Current Limiting

s

Very Low Quiescent Current: 12

µA

s

Up to 1.5A Continuous Output Current

s

Fixed Frequency Operation Up to 3MHz

s

0.5V to 4.5V Input Range

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2.4V to 5.25V Adjustable Output Voltage

s

Guaranteed 1V Start-Up

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Programmable Current Limit

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Programmable Soft-Start

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Synchronizable Oscillator

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Manual or Automatic Burst Mode

s

Low-Battery Comparator

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<1

µA Shutdown Current

s

1.22V Reference Output Voltage

s

Small (4mm

× 4mm) Thermally Enhanced QFN

Package

3A, 3MHz Micropower

Synchronous Boost Converter

with Output Disconnect

Burst Mode is a registered trademark of Linear Technology Corporation.

The LTC

frequency, step-up DC/DC converter with true output dis-

connect and inrush current limiting. The device includes a

0.10

Ω N-channel MOSFET switch and a 0.14Ω P-channel

synchronous rectifier. This product has the ability to sim-

ply program the output voltage, switching frequency, cur-

rent limit, soft-start, Burst Mode threshold and loop

compensation with external passive components.

Quiescent current is only 12

µA during Burst Mode opera-

tion, maximizing battery life in portable applications. The

oscillator frequency can be programmed up to 3MHz and

can be synchronized to an external clock applied to the

SYNC pin. An open-drain uncommitted low-battery com-

parator is included. The part maintains operation in

applications with a secondary cell powering the output

voltage during shutdown.

Other features include: 1

µAshutdown,antiringingcontrol,

thermal limit and reference output.

The LTC3421 is available in a small 4mm

× 4mm QFN

package.

SHDN

ENB

LBI

LBO

SYNC

FB

BURST

221

14

15

16

18

17

19

20

1

24

9

13

12

11

10

5

6

8

7

22

23

3

4

SW SW

L1

4.7

µH

SW

SS

GND

LTC3421

0.1

µF

0.1

µF

470pF

C5*

22

µF

C1*

4.7

µF

1.8V TO 3V

2

CELLS

28k

20k

100k

340k

3.3V

1.2A

200k

3421 TA01

45.3k

*LOCATE COMPONENTS CLOSE TO PINS

C1: TAIYO YUDEN JMK212BJ106MM

PGND PGND PGND

C5: TAIYO YUDEN JMK325BJ226MM

L1: TDK RLF7030T-4R7M3R4

2-Cell to 3.3V Efficiency

OUTPUT CURRENT (mA)

30

90

100

20

10

80

50

70

60

40

0.1

10

100

1000

3421 G02

0

1

Burst Mode OPERATION

DESCRIPTIO

FEATURES

APPLICATIO S

TYPICAL APPLICATIO