1

LTC1622

Low Input Voltage

Current Mode Step-Down

DC/DC Controller

The LTC

down DC/DC controller providing excellent AC and DC load

and line regulation. The device incorporates an accurate

undervoltage feature that shuts the LTC1622 down when

the input voltage falls below 2V.

The LTC1622 boasts a

±1.9%outputvoltageaccuracyand

consumes only 350

µA of quiescent current. For applica-

tions where efficiency is a prime consideration and the

load current varies from light to heavy, the LTC1622 can

be configured for Burst Mode

operation enhances low current efficiency and extends

battery run time. Burst Mode operation is inhibited during

synchronization or when the SYNC/MODE pin is pulled low

to reduce noise and possible RF interference.

High constant operating frequency of 550kHz allows the

use of a small inductor. The device can also be synchro-

nized up to 750kHz for special applications. The high

frequency operation and the available 8-lead MSOP pack-

age create a high performance solution in an extremely

small amount of PCB area.

To further maximize the life of the battery source, the

P-channel MOSFET is turned on continuously in dropout

(100% duty cycle). In shutdown, the device draws a mere

15

µA.

s

1- or 2-Cell Li-Ion Powered Applications

s

Cellular Telephones

s

Wireless Modems

s

Portable Computers

s

Distributed 3.3V, 2.5V or 1.8V Power Systems

s

Scanners

s

Battery-Powered Equipment

s

High Efficiency

s

Constant Frequency 550kHz Operation

s

s

Multiampere Output Currents

s

OPTI-LOOP

s

Selectable, Burst Mode Operation

s

Low Dropout Operation: 100% Duty Cycle

s

Synchronizable up to 750kHz

s

Current Mode Operation for Excellent Line and Load

Transient Response

s

Low Quiescent Current: 350

µA

s

Shutdown Mode Draws Only 15

µA Supply Current

s

±1.9% Reference Accuracy

s

Available in 8-Lead MSOP

Burst Mode and OPTI-LOOP are a trademarks of Linear Technology Corporation.

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

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

Figure 1. High Efficiency Step-Down Converter

2

4

1

8

7

5

6

3

SYNC/MODE

RUN/SS

L1

4.7

µH

R2

0.03

Ω

D1

IR10BQ015

Si3443DV

R3

159k

2.5V

1.5A

R1

10k

C3

220pF

C1: TAIYO YUDEN CERAMIC EMK325BJ106MNT

C2: SANYO POSCAP 6TPA47M

D1: INTERNATIONAL RECTIFIER IR10BQ015

2.5V TO 8.5V

R4

75k

1622 F01a

470pF

C1

10

µF

10V

LTC1622

C2

47

µF

6V

+

PDRV

GND

L1: MURATA LQN6C-4R7

R2: DALE WSL-1206 0-03

Ω

LOAD CURRENT (mA)

100

90

80

70

60

50

40

1

100

1000

5000

1622 F01b

10

Efficiency vs Load Current with

Burst Mode Operation Enabled