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LTC1701

1MHz Step-Down

DC/DC Converter in SOT-23

December 1999

Final Electrical Specifications

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-

tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

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PDAs/Palmtop PCs

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Digital Cameras

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Cellular Phones

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Portable Media Players

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PC Cards

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Handheld Equipment

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

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Tiny 5-Lead SOT-23 Package

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Uses Tiny Capacitors and Inductor

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High Frequency Operation: 1MHz

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High Output Current: 500mA

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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

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Low Quiescent Current: 135

µA

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Low Dropout Operation: 100% Duty Cycle

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Peak Inductor Current Independent of Inductor Value

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Output Voltages from 5V Down to 1.25V

APPLICATIO S

FEATURES

DESCRIPTIO

TYPICAL APPLICATIO

The LTC

down, current mode, DC/DC converter. Intended for small

to medium power applications, it operates from 2.5V to

5.5V input voltage range and switches 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. With no load, the converter draws only 135

µA.

In shutdown, it draws less than 1

µA, making it ideal for

current sensitive applications.

In dropout, the internal P-channel MOSFET switch is

turned on continuously, thereby maximizing battery life.

Its small size and switching frequency enables the com-

plete 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 F01

(2.5V/

500mA)

2.5V TO

5.5V

+

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

Efficiency Curve

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

LOAD CURRENT (mA)

1

10

100

1000

100

95

90

85

80

75

70

1701 F01a