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LTC1433/LTC1434

450mA, Low Noise

Current Mode Step-Down

DC/DC Converters

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Cellular Telephones

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Portable Instruments

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Wireless Modems

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RF Communications

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Distributed Power Systems

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Scanners

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Battery-Powered Equipment

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High Efficiency: Up to 93%

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Constant Frequency Adaptive Power

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Input Voltage Range: 3V to 13.5V

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Internal 0.6

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Low Dropout Operation: 100% Duty Cycle

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Low-Battery Detector

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Internal Power-On Reset Timer

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Current Mode Operation for Excellent Line and Load

Transient Response

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Low Quiescent Current: 470

µA

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Shutdown Mode Draws Only 15

µA Supply Current

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±1% Reference Accuracy

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Available in 16- and 20-Lead Narrow SSOP

FEATURES

The LTC

lated step-down DC/DC converters. By utilizing current

mode switching techniques, they provide excellent AC and

DC load and line regulation. Both devices operate at a fixed

frequency with the LTC1434 phase-lockable to an external

clock signal.

Both devices incorporate two internal P-channel power

MOSFETs with a parallel combined resistance of 0.6

Ω (at

a supply of 10V). The Adaptive Power output stage selec-

tively drives one or both of the switches at frequencies up

to 700kHz to reduce switching losses and maintain high

efficiencies at low output currents.

The LTC1433/LTC1434 are capable of supplying up to

450mA of output current and boasts a

±2.4% output

voltage accuracy. An internal low-battery detector has the

same level of accuracy as the output voltage. A power-on

reset timer (POR) is included which generates a signal

within 5% of the regulated output voltage.

Ideal for current sensitive applications, the devices draw

only 470

µA of quiescent current. In shutdown the devices

draw a mere 15

µA. To further maximize the life of the

battery source, the internal P-channel MOSFET switch is

turned on continuously in dropout.

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

Adaptive Power is a trademark of Linear Technology Corporation.

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

SSW

NC

BSW

NC

SGND

RUN/SS

LBO

LBI

POR

LTC1433

PGND

68

µF**

20V

0.1

µF

0.1

µF

100

µF*

10V

D1: MOTOROLA MBRS130LT3

L1: COILCRAFT D03316-104

3.3V

D1

L1

100

µH

POWER-ON

RESET

3.5V TO 12V

680pF

5.1k

10k

6800pF

47pF

1433/34 F01

*AVX TPSD107M010R0100

** AVX TPSE686M020R0150

+

Figure 1. High Efficiency Step-Down Converter

LOAD CURRENT (A)

0.001

60

70

80

0.01

0.1

1

1433/34 TA01

50

40

100

90

LTC1433 Efficiency for