© 2000 SEMTECH CORP.

652 MITCHELL ROAD NEWBURY PARK CA 91320

LOW VOLTAGE, BOOST DC-DC

CONTROLLER

SC1408

August 22, 2000

1

TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com

ORDERING INFORMATION

Part Number

(1)

Package

Temp. Range (T

SC1408IS.TR

SO-8

-40° to +85°C

SC1408IMS.TR

MSOP-8

Note:

(1) Only available in tape and reel packaging. A reel

contains 2500 devices.

DESCRIPTION

The SC1408 is a low voltage boost controller that oper-

ates from a 1.8V to 16.5V input range. A shutdown pin

allows the user to turn the controller off reducing sup-

ply current to less than 2µA typical. Output voltage can

be preset to 5V or is adjustable from 3V to 16.5V with

a resistor divider. The controller changes frequency in

low load conditions to improve efficiency.

The SC1408 was designed for two cell Alkaline or sin-

gle cell Lithium Ion battery applications. With the

proper external components it can be used as a boost

converter or a buck/boost converter.

A current sense is implemented with an external resis-

tor that is not in the load current path.

The SC1408 operates in “bootstrapped” mode. When

the input voltage to the device is less than 2.5V during

startup, a low voltage 50% fixed duty cycle oscillator is

switched in to initiate boost action.

FEATURES

APPLICATIONS

TYPICAL APPLICATION - BOOST CONFIGURATION

Vin (1.8V to 16.5V)

Vout (3V to 16.5V)

U1

SC1408IS

8

1

2

3

4

5

6

7

ISENSE

GATE

BST

FB

SHDN

REF

AGND

GND

L1

R2

Q1

D1

+

C2

R4

R3

+

C3

C5