LM3671

2MHz , 600mA Step-Down DC-DC Converter in SOT23-5

General Description

The LM3671 step-down DC-DC converter is optimized for

powering ultra-low voltage circuits from a single Li-Ion cell or

3 cell NiMH/NiCd batteries. It provides up to 600mA load

current, over an input voltage range from 2.8V to 5.5V. There

are several different fixed voltage output options available as

well as an adjustable output voltage version.

The device offers superior features and performance for

mobile phones and similar portable applications with com-

plex power management systems. Automatic intelligent

switching between PWM low-noise and PFM low-current

mode offers improved system control. During full-power op-

eration, a fixed-frequency 2 MHz (typ). PWM mode drives

loads from

∼70 mA to 600 mA max. Hysteretic PFM mode

extends the battery life through reduction of the quiescent

current to 16 µA (typ) at light loads and system standby.

Internal synchronous rectification provides high efficiency. In

shutdown mode (Enable pin pulled low) the device turns off

and reduces battery consumption to 0.01 µA (typ).

The LM3671 is available in a SOT23-5 package with Pb and

No Pb (Lead free) versions. A high switching frequency - 2

MHz (typ) - allows use of tiny surface-mount components.

Only three external surface-mount components, an inductor

and two ceramic capacitors, are required.

Features

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16 µA typical quiescent current

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600 mA maximum load capability

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2 MHz PWM fixed switching frequency (typ)

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Automatic PFM/PWM mode switching

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Available in fixed output voltages and adjustable version

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SOT23-5 package

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Internal synchronous rectification for high efficiency

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Internal soft start

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0.01 µA typical shutdown current

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Operates from a single Li-Ion cell or 3 cell NiMH/NiCd

batteries

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Only three tiny surface-mount external components

required (one inductor, two ceramic capacitors)

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Current overload and Thermal shutdown protection

Applications

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Mobile phones

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PDAs

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MP3 players

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W-LAN

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Portable instruments

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Digital still cameras

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Portable Hard disk drives

Typical Application Circuits

20108401

FIGURE 1. Typical Application Circuit

November 2004

© 2004 National Semiconductor Corporation

DS201084

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