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LT1767/LT1767-1.8/

LT1767-2.5/LT1767-3.3/LT1767-5

sn1767 1767fas

Monolithic 1.5A, 1.25MHz

Step-Down Switching Regulators

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1.5A Switch in a Small MSOP Package

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Constant 1.25MHz Switching Frequency

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High Power Exposed Pad (MS8E) Package

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Wide Operating Voltage Range: 3V to 25V

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High Efficiency 0.22

Ω Switch

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1.2V Feedback Reference Voltage

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Fixed Output Voltages of 1.8V, 2.5V, 3.3V, 5V

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2% Overall Output Tolerance

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Uses Low Profile Surface Mount Components

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Low Shutdown Current: 6

µA

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Synchronizable to 2MHz

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Current Mode Loop Control

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Constant Maximum Switch Current Rating at All Duty

Cycles*

The LT

regulator. A high efficiency 1.5A, 0.22

Ω switch is included

on the die together with all the control circuitry required to

complete a high frequency, current mode switching regu-

lator. Current mode control provides fast transient re-

sponse and excellent loop stability.

New design techniques achieve high efficiency at high

switching frequencies over a wide operating range. A low

dropout internal regulator maintains consistent perfor-

mance over a wide range of inputs from 24V systems to Li-

Ion batteries. An operating supply current of 1mA im-

proves efficiency, especially at lower output currents.

Shutdown reduces quiescent current to 6

µA. Maximum

switch current remains constant at all duty cycles. Syn-

chronization allows an external logic level signal to in-

crease the internal oscillator from 1.4MHz to 2MHz.

The LT1767 is available in an 8-pin MSOP fused leadframe

package and a low thermal resistance exposed pad pack-

age. Full cycle-by-cycle short-circuit protection and ther-

mal shutdown are provided. High frequency operation

allows the reduction of input and output filtering compo-

nents and permits the use of chip inductors.

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DSL Modems

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Portable Computers

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Wall Adapters

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Battery-Powered Systems

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Distributed Power

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

Efficiency vs Load Current

12V to 3.3V Step-Down Converter

BOOST

LT1767-3.3

OUTPUT

3.3V

1.2A*

12V

1767 TA01

C2

0.1

µF

1.5nF

4.7k

D1

UPS120

C1

10

µF

CERAMIC

C3

2.2

µF

CERAMIC

D2

CMDSH-3

L1

5

µH

FB

SHDN

OPEN

OR

HIGH

= ON

GND

SYNC

*MAXIMUM OUTPUT CURRENT IS SUBJECT TO THERMAL DERATING.

LOAD CURRENT (A)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1767 TA01a

95

90

85

80

75

70

*Patent Pending

APPLICATIO S

FEATURES

TYPICAL APPLICATIO

DESCRIPTIO