October 28, 2008
LM3671
2MHz, 600mA Step-Down DC-DC Converter
General Description
Features
The LM3671 step-down DC-DC converter is optimized for
powering low voltage circuits from a single Li-Ion cell battery
and input voltage rails from 2.7V to 5.5V. It provides up to
600mA load current, over the entire input voltage range.
There are several different fixed voltage output options avail-
able as well as an adjustable output voltage version range
from 1.1V to 3.3V.
16 µA typical quiescent current
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600 mA maximum load capability
2 MHz PWM fixed switching frequency (typ.)
Automatic PFM/PWM mode switching
Internal synchronous rectification for high efficiency
Internal soft start
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The device offers superior features and performance for mo-
bile phones and similar portable systems. Automatic intelli-
gent switching between PWM low-noise and PFM low-current
mode offers improved system control. During PWM mode, the
device operates at a fixed-frequency of 2 MHz (typ.). Hys-
teretic PFM mode extends the battery life by reducing the
quiescent current to 16 µA (typ.) during light load and standby
operation. Internal synchronous rectification provides high ef-
ficiency during PWM mode operation. In shutdown mode, the
device turns off and reduces battery consumption to 0.01 µA
(typ.).
0.01 µA typical shutdown current
Operates from a single Li-Ion cell battery
Only three tiny surface-mount external components
required (one inductor, two ceramic capacitors)
Current overload and Thermal shutdown protection
Available in fixed output voltages and adjustable version
SOT23-5, 5-bump micro SMD and 6-pin LLP packages
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Applications
Mobile phones
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The LM3671 is available in SOT23-5, tiny 5-bump micro SMD
and a 6-pin LLP packages in leaded (PB) and lead-free (NO
PB) versions. A high switching frequency of 2 MHz (typ.) al-
lows use of tiny surface-mount components. Only three ex-
ternal surface-mount components, an inductor and two
ceramic capacitors, are required.
PDAs
MP3 players
W-LAN
Portable instruments
Digital still cameras
Portable Hard disk drives
Typical Application Circuits
20108401
FIGURE 1. Typical Application Circuit
© 2008 National Semiconductor Corporation
201084
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