LT1500 데이터 시트보기 (PDF) - Linear Technology

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LT1500

Adaptive-Frequency Current Mode Switching Regulators

Linear Technology 

LT1500/LT1501

Adaptive-Frequency

Current Mode Switching Regulators

FEATURES

s Low Noise Adaptive-Frequency Current Mode

Operation Avoids Low Frequency Noise at

Most Load Currents

s Can Be Externally Synchronized (LT1500)

s Micropower Quiescent Current: 200µA

s Shutdown Current: 8µA Typ

s Internal Loop Compensation

s Low-Battery Comparator Active in Shutdown

s Minimum Input Voltage: 1.8V Typ

s Additional Negative Voltage Feedback Pin (LT1500)

s Up to 500kHz Switching Frequency

s Uses Low Profile, Low Cost Surface Mount Inductors

U

APPLICATIONS

s Portable Instrumentation

s Battery Operated Systems

s PDA’s

s Standby Power

DESCRIPTION

The LT®1500 is an adaptive-frequency current mode step-

up switching regulator with an internal power switch that

is rated up to 700mA. In contrast to pulse skipping

switching regulators, the LT1500 uses a current mode

topology that provides lower noise operation and im-

proved efficiency. Only at very light loads is Burst ModeTM

activated to give high efficiency and micropower opera-

tion. High switching frequency (up to 500kHz) allows very

small inductors to be used, along with ceramic capacitors

if desired.

The LT1500 operates with input voltages from 1.8V to 15V

and has only 200µA operating current dropping to 8µA in

shutdown. A low-battery comparator is included which

stays alive in shutdown. A second output feedback pin

with negative polarity allows negative output voltages to

be regulated when the switcher is connected up as a Cuk

or a flyback converter.

Two package types are available. The LT1500 comes in a

14-pin SO package, with two options available for fixed

output (3.3V or 5V) or adjustable operation. A reduced

feature part, the LT1501, comes in the smaller 8-pin SO

package with internal frequency compensation. It is also

available in adjustable and fixed output voltage versions.

, LTC and LT are registered trademarks of Linear Technology Corporation.

Burst Mode is a trademark of Linear Technology Corporation.

TYPICAL APPLICATION

2-Cell to 5V Converter

D1

22µH† MBR0520L

2 EACH

NiCd OR

ALKALINE

CELLS

301k

1%

+ 33µF*

6V

VIN ISENSE

SHDN

SW

LT1501-5

LBI

OUT

301k

1%

LBO GND

1nF

LOW-BATTERY FLAG

(USE EXTERNAL PULL-UP)

5V, 200mA

220µF**

10V

TANT

* AVX, TPSC107M006R0150

** AVX, TPSD107M010 R0100

† SUMIDA CD73-220, CD54-220

OR CD43-220. SELECT ACCORDING

TO MAXIMUM LOAD CURRENT

LT1500/01 • TA01

1

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