1

LT1176/LT1176-5

Step-Down

Switching Regulator

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FEATURE

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1.2A On-Board Switch

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100kHz Switching Frequency

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Excellent Dynamic Behavior

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DIP and Surface Mount Packages

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Only 8mA Quiescent Current

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Preset 5V Output Available

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Operates Up to 35V Input

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Micropower Shutdown Mode

APPLICATI

TYPICAL

Basic 5V Positive Buck Converter

5V Buck Converter Efficiency

tion. The power switch, all oscillator and control circuitry,

and all current limit components are included on the chip.

The topology is a classic positive “buck” configuration but

several design innovations allows this device to be used as

a positive-to-negative converter, a negative boost con-

verter, and as a flyback converter. The switch output is

specified to swing below ground.

The LT1176 uses a true analog multiplier in the feedback

loop. This makes the device respond nearly instantaneously

to input voltage fluctuations and makes loop gain indepen-

dent of input voltage. As a result, dynamic behavior of the

regulator is significantly improved over previous designs.

On-chip pulse by pulse current limiting makes the LT1176

nearly bust-proof for output overloads or shorts. The input

voltage range as a buck converter is 8V to 35V, but a self-

boot feature allows input voltages as low as 5V in the

inverting and boost configurations.

The LT1176 is available in a low cost 8-lead DIP package

with frequency preset at 100kHz and current limit at 1.7A An

adjustable output is offered as well as a preset 5V version.

For further design details and application help, see the

LT1074/LT1076 data sheet and Application Note 44.

DESCRIPTIO

The LT1176 is a 1A monolithic bipolar switching regulator

which requires only a few external parts for normal opera-

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APPLICATI

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Buck Converter with Output Voltage Range of

2.5V to 30V

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Positive-to-Negative Converter

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Negative Boost Converter

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Mulitple Output Buck Converter

GND

LT1176-5

R3

2.7k

C2

0.01

µF

1N5819

+

C3

100

µF

+

C1

470

µF

25V

LT1176/76-5 • TA01

5V, 0.8A

10V T0 35V

L1*

100

µH

*COILTRONICS #100-1-52

PULSE ENGINEERING, INC. #PE-92102

HURRICANE #HL-AG210LL

THESE ARE LOW COST POWDERED IRON CORES. OPTIMUM EFFICIENCY

AND SMALLEST SIZE IS OBTAINED BY USING A LOW LOSS CORE SUCH

AS MAGNETICS INC. KOOL M

µ. SEE EFFICIENCY GRAPH.

SENSE

LOAD CURRENT (A)

60

70

80

90

0.2

0.4

0.6

0.8

LT1176/76-5 • TA02

1.0

0.1

0.3

0.5

0.7

0.9

L = 100

µH ON MAGNETICS INC.

SIZE T-50 KOOL M

µ CORE