© 2000 SEMTECH CORP.

652 MITCHELL ROAD NEWBURY PARK CA 91320

400mA SmartLDO

TM

SC1534

PRELIMINARY - July 26, 2000

1

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

FEATURES

APPLICATIONS

ABSOLUTE MAXIMUM RATINGS

Parameter

Symbol

Maximum

Units

Input Supply Voltage

VIN

-0.5 to +7

V

Auxiliary Supply Voltage

VAUX

-0.5 to +7

V

LDO Output Current

I

O

10 to 400

mA

Operating Ambient

Temperature Range

T

A

-5 to +70

°C

Operating Junction

Temperature Range

T

J

-5 to +125

°C

Storage Temperature

Range

T

STG

-65 to +150

°C

Lead Temperature

(Soldering) 10 Sec

T

LEAD

300

°C

Thermal Impedance

Junction to Ambient

SO-8

(1)

TO-263

θ

JA

65

60

°C/W

Thermal Impedance

Junction to Case

SO-8

TO-263

θ

J C

39

3

°C/W

ESD Rating

ESD

2

kV

ORDERING INFORMATION

Part Number

(1)

Package

SC1534CM.TR

TO-263-5L

SC1534CS.TR

SO-8

Note:

(1) Only available in tape and reel packaging.

BLOCK DIAGRAM

DESCRIPTION

The SC1534 is designed to maintain a glitch-free 3.3V

output when at least one of two inputs, 5V (VIN) and

3.3V (VAUX), is present.

Whenever VIN exceeds a predetermined threshold

value, the internal 3.3V linear regulator is enabled, and

DR is pulled high.

When VIN falls below a lower threshold value, DR is

pulled low and the internal linear regulator is turned off.

DR has been designed to drive the gate of an external

low threshold P-channel MOSFET, which can be used

to connect the 3.3V supply directly to the regulator out-

put. This ensures an uninterrupted 3.3V output even if

VIN falls out of specification. A maximum R

200m

Ω is recommended.

When both supplies are simultaneously available, the

drive pin (DR) will be pulled High, turning off the exter-

nal PMOS switch.

The internal 5V detector has its upper threshold (for

VIN rising) set to 4.22V (typical) while the lower thresh-

old (for VIN falling) is at 4.05V (typical) giving a hys-

teresis of approximately 170mV.

The SC1534 is available in the popular SO-8 and 5-

lead TO-263 surface mount packages.

Note:

(1) 1 inch square of 1/16” FR-4, double sided, 1 oz. mini-

mum copper weight.

PIN CONFIGURATION

TO-263-5L

SO-8

Top View