1

LT1170/LT1171/LT1172

100kHz, 5A, 2.5A and 1.25A

High Efficiency Switching Regulators

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Wide Input Voltage Range: 3V to 60V

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Low Quiescent Current: 6mA

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Internal 5A Switch (2.5A for LT1171,

1.25A for LT1172)

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Shutdown Mode Draws Only 50

µA Supply Current

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Very Few External Parts Required

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Self-Protected Against Overloads

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Operates in Nearly All Switching Topologies

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Flyback-Regulated Mode Has Fully Floating Outputs

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Comes in Standard 5-Pin Packages

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LT1172 Available in 8-Pin MiniDIP and Surface Mount

Packages

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Can Be Externally Synchronized

The LT

switching regulators. They can be operated in all standard

switching configurations including buck, boost, flyback,

forward, inverting and “Cuk.” A high current, high effi-

ciency switch is included on the die along with all oscilla-

tor, control and protection circuitry. Integration of all

functions allows the LT1170/LT1171/LT1172 to be built in

a standard 5-pin TO-3 or TO-220 power package as well as

the 8-pin packages (LT1172). This makes them extremely

easy to use and provides “bust proof” operation similar to

that obtained with 3-pin linear regulators.

The LT1170/LT1171/LT1172 operate with supply volt-

ages from 3V to 60V, and draw only 6mA quiescent

current. They can deliver load power up to 100W with no

external power devices. By utilizing current-mode switch-

ing techniques, they provide excellent AC and DC load and

line regulation.

The LT1170/LT1171/LT1172 have many unique features

not found even on the vastly more difficult to use low

power control chips presently available. They use adaptive

antisat switch drive to allow very wide ranging load cur-

rents with no loss in efficiency. An externally activated

shutdown mode reduces total supply current to 50

µA

typically for standby operation.

Boost Converter (5V to 12V)

Maximum Output Power*

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

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Logic Supply 5V at 10A

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5V Logic to

±15V Op Amp Supply

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Battery Upconverter

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Power Inverter (+ to –) or (– to +)

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Fully Floating Multiple Outputs

USER NOTE:

This data sheet is only intended to provide specifications, graphs, and a general functional description

of the LT1170/LT1171/LT1172. Application circuits are included to show the capability of the

LT1170/LT1171/LT1172. A complete design manual (AN19) should be obtained to assist in

developing new designs. This manual contains a comprehensive discussion of both the LT1070 and

the external components used with it, as well as complete formulas for calculating the values of these

components. The manual can also be used for the LT1170/LT1171/LT1172 by factoring in the higher

frequency. A CAD design program called SwitcherCAD

SwitcherCAD is a trademark of Linear Technology Corporation.

DESCRIPTIO

FEATURES

APPLICATIO S

TYPICAL APPLICATIO

1170/1/2 TA01

D1

MBR330

C2

1000

µF

C1

1

µF

R1

10.7k

1%

R2

1.24k

1%

LT1170

GND

5V

R3

1k

*REQUIRED IF INPUT LEADS

≥ 2"

** COILTRONICS 50-2-52

PULSE ENGINEERING 92114

FB

OUTPUT

FILTER

L2

10

µH

L1**

50

µH

C3

100

µF

12V

1A

C3*

100

µF

+

+

INPUT VOLTAGE (V)

0

100

80

60

40

20

0

40

LT1170/1/2 TA02

10

20

30

50

* ROUGH GUIDE ONLY. BUCK MODE

SPECIAL TOPOLOGIES DELIVER

MORE POWER.

** DIVIDE VERTICAL POWER SCALE

BY TWO FOR LT1171, BY FOUR

FOR LT1172.

BOOST

BUCK-BOOST

FLYBACK

BUCK-BOOST

LT1170