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LT1500/LT1501

Adaptive-Frequency

Current Mode Switching Regulators

FEATURES

The LT

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 Mode

TM

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 200

µA 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.

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Low Noise Adaptive-Frequency Current Mode

Operation Avoids Low Frequency Noise at

Most Load Currents

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Can Be Externally Synchronized (LT1500)

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Micropower Quiescent Current: 200

µA

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Shutdown Current: 8

µA Typ

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Internal Loop Compensation

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Low-Battery Comparator Active in Shutdown

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Minimum Input Voltage: 1.8V Typ

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Additional Negative Voltage Feedback Pin (LT1500)

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Up to 500kHz Switching Frequency

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Uses Low Profile, Low Cost Surface Mount Inductors

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

Burst Mode is a trademark of Linear Technology Corporation.

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Portable Instrumentation

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Battery Operated Systems

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PDA’s

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Standby Power

2-Cell to 5V Converter

SHDN

LBO

LBI

SW

GND

OUT

LT1501-5

+

1nF

301k

1%

301k

1%

LOW-BATTERY FLAG

(USE EXTERNAL PULL-UP)

33

µF*

6V

10V

TANT

2 EACH

NiCd OR

ALKALINE

CELLS

22

5V, 200mA

LT1500/01 • TA01

AVX, TPSC107M006R0150

AVX, TPSD107M010 R0100

SUMIDA CD73-220, CD54-220

OR CD43-220. SELECT ACCORDING

TO MAXIMUM LOAD CURRENT

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**

†

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MBR0520L