© 1997 SEMTECH CORP.

652 MITCHELL ROAD NEWBURY PARK CA 91320

HIGH-EFFICIENCY STEP-DOWN

DC-DC CONVERTER

SC1578

January 29, 1998

FEATURES

DESCRIPTION

The SC1578 is a high performance step-down DC-DC

converter, designed to drive an external P-channel

MOSFET to generate programmable output voltages.

Two main schemes of pulse-skipping and pulse-

frequency modulation are employed to maintain low

quiescent current and high conversion efficiency over

wide ranges of input voltage and loads. The SC1578

delivers 10mA to 2A of output current with 87%-93%

efficiency at V

comparator with both inverting and non-inverting inputs

uncommitted is included to provide the crucial function

of either current limit protection or constant output

current control. When the SC1578 is used in a high-

side current sensing step-down constant current

source, the efficiency is typically greater than 90%.

Duty cycle can be adjusted to greater than 90% by

connecting a resistor from the DUTY pin to V

Quiescent current is about 90µA and can be reduced

to 8µA in shutdown mode. With a switching frequency

range of 90kHz to 280kHz, small size switching

components may be used, which is ideal for battery

powered portable equipment.

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

BLOCK DIAGRAM

APPLICATIONS

ABSOLUTE MAXIMUM RATINGS

Parameter

Symbol

Maximum

Units

Supply Voltage

V

IN

24

V

Duty Voltage

V

DUTY

20

V

SHDN Voltage

V

SHDN

15

V

Operating

Temperature Range

T

A

0 to 70

°C

Storage Temperature

Range

T

STG

-65 to 150

°C

PIN CONFIGURATION

ORDERING INFORMATION

DEVICE

(1)

PACKAGE

SC1578CS

SO-8

Note:

(1) Add suffix ‘TR’ for tape and reel.