1

LTC1701/LTC1701B

DESCRIPTIO

APPLICATIO S

1MHz Step-Down

DC/DC Converters in SOT-23

s

PDAs/Palmtop PCs

s

Digital Cameras

s

Cellular Phones

s

Portable Media Players

s

PC Cards

s

Handheld Equipment

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

s

Tiny 5-Lead SOT-23 Package

s

Uses Tiny Capacitors and Inductor

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High Frequency Operation: 1MHz

s

High Output Current: 500mA

s

s

High Efficiency: Up to 94%

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Current Mode Operation for Excellent Line

and Load Transient Response

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Short-Circuit Protected

s

Low Quiescent Current: 135

µA (LTC1701)

s

Low Dropout Operation: 100% Duty Cycle

s

s

Peak Inductor Current Independent of Inductor Value

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Output Voltages from 5V Down to 1.25V

The LTC

step-down, current mode, DC/DC converters. Intended for

low to medium power applications, they operate from 2.5V

to 5.5V input voltage range and switch at 1MHz, allowing

the use of tiny, low cost capacitors and inductors 2mm or

less in height. The output voltage is adjustable from 1.25V

to 5V. A built-in 0.28

Ω switch allows up to 0.5A of output

current at high efficiency. OPTI-LOOP

allows the transient response to be optimized over a wide

range of loads and output capacitors.

The LTC1701 incorporates automatic power saving Burst

Mode

load current drops below the level required for continuous

operation. The LTC1701B operates continuously to very

low load currents to provide low ripple at the expense of

light load efficiency. With no load, the LTC1701 draws only

135

µA. In shutdown, both devices draw less than 1µA,

making them ideal for current sensitive applications.

Their small size and switching frequency enables a

complete DC/DC converter function to consume less than

0.3 square inches of PC board area.

SW

GND

LTC1701

D1

L1

4.7

µH

R4

1M

C1: TAIYO YUDEN JMK316BJ106ML

C2: SANYO POSCAP 6TPA47M

D1: MBRM120L

L1: SUMIDA CD43-4R7

R3

5.1k

C3

330pF

C1

10

µF

+

R2

121k

R1

121k

C2

47

µF

1701 F01a

(2.5V/

500mA)

2.5V TO

5.5V

+

Figure 1. 2.5V/500mA Step-Down Regulator

Efficiency Curve

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

FEATURES

LOAD CURRENT (mA)

1

10

100

1000

100

95

90

85

80

75

70

65

60

55

50

1701 F01b

LTC1701

LTC1701B