LM2717

Dual Step-down DC/DC Converter

General Description

The LM2717 is composed of two PWM DC/DC buck (step-

down) converters. The first converter is used to generate a

fixed output voltage of 3.3V. The second converter is used to

generate an adjustable output voltage. Both converters fea-

ture low R

Ω) internal switches for maximum effi-

ciency. Operating frequency can be adjusted anywhere be-

tween 300kHz and 600kHz allowing the use of small external

components. External soft-start pins for each enables the

user to tailor the soft-start times to a specific application.

Each converter may also be shut down independently with

its own shutdown pin. The LM2717 is available in a low

profile 24-lead TSSOP package ensuring a low profile over-

all solution.

Features

n

Fixed 3.3V output buck converter with a 2.2A, 0.16

Ω,

internal switch

n

Adjustable buck converter with a 3.2A, 0.16

Ω, internal

switch

n

Operating input voltage range of 4V to 20V

n

Input undervoltage protection

n

300kHz to 600kHz pin adjustable operating frequency

n

Over temperature protection

n

Small 24-Lead TSSOP package

Applications

n

TFT-LCD Displays

n

Handheld Devices

n

Portable Applications

n

Laptop Computers

Typical Application Circuit

20078501

PRELIMINARY

May 2005

© 2005 National Semiconductor Corporation

DS200785

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