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LTC1649

3.3V Input High Power

Step-Down Switching

Regulator Controller

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High Power 3.3V to 1.xV-2.xV Switching Regulator

Controller: Up to 20A Output

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All N-Channel External MOSFETs

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Provides 5V MOSFET Gate Drive with 3.3V Input

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Excellent Output Regulation:

±1% Over Line, Load

and Temperature Variations

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Constant Frequency Operation Minimizes

Inductor Size

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High Efficiency: Over 90% Possible

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No Low-Value Sense Resistor Needed

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Available in 16-Lead SO Package

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3.3V Input Power Supply for Low Voltage

Microprocessors and Logic

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Low Input Voltage Power Supplies

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High Power, Low Voltage Regulators

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Local Regulation for Multiple Voltage Distributed

Power Systems

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

The LTC

regulator controller optimized for use with very low supply

voltages. It operates from 2.7V to 5V input, and provides

a regulated output voltage from 1.26V to 2.5V at up to 20A

load current. A typical 3.3V to 2.5V application features

efficiency above 90% from 1A to 10A load. The LTC1649

uses a pair of standard 5V logic-level N-channel external

MOSFETs, eliminating the need for expensive P-channel

or super-low-threshold devices.

The LTC1649 shares its internal switching architecture

with the LTC1430, and features the same

±1% line, load

and temperature regulation characteristics. Current limit

is user-adjustable without requiring an external low-value

sense resistor. The LTC1649 uses a 200kHz switching

frequency and voltage mode control, minimizing external

component count and size. Shutdown mode drops the

quiescent current to below 10

µA.

The LTC1649 is available in the 16-pin narrow SO package.

2.5V

@15A

SHDN

1

µF

G2

FB

3.3V

LTC1649

G1

COMP

SS

GND

1

µF

10

µF

MBR0530

0.1

µF

0.01

µF

IRF7801 = INTERNATIONAL RECTIFIER

MBR0530 = MOTOROLA

*12TS-1R2HL = PANASONIC

7.5k

1.2

µH

C1

220pF

10

µF

MBR0530

50k

22

Ω

1k

Q3

IRF7801

Q1, Q2

IRF7801

TWO IN

PARALLEL

4400

µF

3300

µF

SHDN

R2

12.7k

R1

12.4k

1649 TA01

+

0.33

µF

+

+

+

3.3V to 2.5V, 15A Converter

LTC1649 Efficiency

LOAD CURRENT (A)

1649 TA02

0.1

1

10

100

90

80

70

60

50

40

APPLICATIO S

FEATURES

TYPICAL APPLICATIO

DESCRIPTIO