LINEAR TECHNOLOGY LTC1474 LTC1475 Data Sheet Manual

LTC1474/LTC1475

Low Quiescent Current High Efficiency Step-Down

Converters

FEATURES DESCRIPTION

High Efficiency: Over 92% Possible The LTC®1474/LTC1475 series are high efficiency step- Very Low Standby Current: 10µA Typ down converters with internal P-channel MOSFET power Available in Space Saving 8-Lead MSOP Package switches that draw only 10µA typical DC supply current at Internal 1.4Ω Power Switch (VIN = 10V) no load while maintaining output voltage. The LTC1474 Wide VIN Range: 3V to 18V Operation uses logic-controlled shutdown while the LTC1475 fea- Very Low Dropout Operation: 100% Duty Cycle tures pushbutton on/off. Low-Battery Detector Functional During Shutdown

The low supply current coupled with Burst Mode TM opera-

Programmable Current Limit with Optional

tion enables the LTC1474/LTC1475 to maintain high effi-

Current Sense Resistor (10m A to 400m A Typ)

ciency over a wide range of loads. These features, along

Short-Circuit Protection

with their capability of 100% duty cycle for low dropout

Few External Components Required

and wide input supply range, make the LTC1474/LTC1475

Active Low Micropower Shutdown: IQ = 6µA Typ

ideal for moderate current (up to 300m A) battery-powered

Pushbutton On/Off (LTC1475 Only)

applications.

3.3V, 5V and Adjustable Output Versions

The peak switch current is user-programmable with an optional sense resistor (defaults to 325m A minimum if not

APPLICATIONS used) providing a simple means for optimizing the design

EF FI CI EN CY

for lower current applications. The peak current control

Cellular Telephones and Wireless Modems

also provides short-circuit protection and excellent start-

4m A to 20m A Current Loop Step-Down Converter

up behavior. A low-battery detector that remains functional

Portable Instruments

in shutdown is provided .

Battery-Operated Digital Devices Battery Chargers The LTC1474/LTC1475 series availability in 8-lead MSOP Inverting Converters and SO packages and need for few additional components Intrinsic Safety Applications provide for a minimum area solution.

, LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a trademark of Linear Technology Corporation.

TYPICAL APPLICATION LTC1474 Efficiency VIN

LOW BATTERY OUT

4V TO 18V

VIN = 5V 0.1µF10µF VIN = 10V

SENSE VFB VIN = 15V

3.3V AT 250m A

LTC1474-3.3

LOW BATTERY IN LBI LBO 100µF

RUN SHDN RUN SW

MBR0530

1474/75 F01 VOUT = 3.3V L1 = SUMIDA CDRH74-101 RSENSE = 0Ω

Figure 1. High Efficiency Step-Down Converter

LOAD CURRENT (m A)

1474/75 TA01