LM3671
2MHz, 600mA Step-Down DC-DC Converter in SOT23-5
and 5-bump Micro SMD
General Description
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.
The device offers superior features and performance for
mobile phones and similar portable systems. Automatic in-
telligent 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). Hysteretic PFM mode extends the battery life by re-
ducing the quiescent current to 16 A (typ) during light load
and standby operation. Internal synchronous rectification
provides high efficiency during PWM mode operation. In
shutdown mode, the device turns off and reduces battery
consumption to 0.01 A (typ).
The LM3671 is available in SOT23-5 and a tiny 5-bump
micro SMD packages in leaded (PB) and lead-free (NO PB)
versions. A high switching frequency of 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
n
16 A typical quiescent current
n
600 mA maximum load capability
n
2 MHz PWM fixed switching frequency (typ)
n
Automatic PFM/PWM mode switching
n
Available in fixed output voltages and adjustable version
n
SOT23-5 and 5-bump micro SMD packages
n
Internal synchronous rectification for high efficiency
n
Internal soft start
n
0.01 A typical shutdown current
n
Operates from a single Li-Ion cell battery
n
Only three tiny surface-mount external components
required (one inductor, two ceramic capacitors)
n
Current overload and Thermal shutdown protection
Applications
n
Mobile phones
n
PDAs
n
MP3 players
n
W-LAN
n
Portable instruments
n
Digital still cameras
n
Portable Hard disk drives
Typical Application Circuits
20108401
FIGURE 1. Typical Application Circuit
October 2005
LM3671
2MHz,
600mA
Step-Down
DC-DC
Converter
in
SOT23-5
and
5-bump
Micro
SMD
2005 National Semiconductor Corporation
DS201084
www.national.com
Typical Application Circuits
(Continued)
Connection Diagram and Package Mark Information
20108431
FIGURE 2. Typical Application Circuit for ADJ version
20108402
FIGURE 3. TopView
SOT23-5 Package NS Package Number MF05A
20108444
FIGURE 4. 5-bump Micro SMD Package NS Package Number TLA05CBA
LM3671
www.national.com
2
Pin Descriptions (SOT23-5)
Pin #
Name
Description
1
V
IN
Power supply input. Connect to the input filter capacitor (Figure 1).
2
GND
Ground pin.
3
EN
Enable pin. The device is in shutdown mode when voltage to this pin is
<
0.4V and
enabled when
>
1.0V. Do not leave this pin floating.
4
FB
Feedback analog input. Connect directly to the output filter capacitor for fixed voltage
versions. For adjustable version external resistor dividers are required (Figure 2). The
internal resistor dividers are disabled for the adjustable version.
5
SW
Switching node connection to the internal PFET switch and NFET synchronous
rectifier.
Pin Descriptions (5-bump Micro SMD)
Pin #
Name
Description
A1
V
IN
Power supply input. Connect to the input filter capacitor (Figure 1).
A3
GND
Ground pin.
C1
EN
Enable pin. The device is in shutdown mode when voltage to this pin is
<
0.4V and
enabled when
>
1.0V. Do not leave this pin floating.
C3
FB
Feedback analog input. Connect directly to the output filter capacitor for fixed voltage
versions. For adjustable version external resistor dividers are required (Figure 2). The
internal resistor dividers are disabled for the adjustable version.
B2
SW
Switching node connection to the internal PFET switch and NFET synchronous
rectifier.
LM3671
www.national.com
3
Ordering Information (SOT23-5)
Voltage Option
Order Number
Spec
Package Marking
Supplied As
ADJ
LM3671MF-ADJ
NOPB
SBTB
1000 units, Tape-and-Reel
LM3671MFX-ADJ
NOPB
3000 units, Tape-and-Reel
LM3671MF-ADJ
1000 units, Tape-and-Reel
LM3671MFX-ADJ
3000 units, Tape-and-Reel
1.2
LM3671MF-1.2
NOPB
SBPB
1000 units, Tape-and-Reel
LM3671MFX-1.2
NOPB
3000 units, Tape-and-Reel
LM3671MF-1.2
1000 units, Tape-and-Reel
LM3671MFX-1.2
3000 units, Tape-and-Reel
1.25
LM3671MF-1.25
NOPB
SDRB
1000 units, Tape-and-Reel
LM3671MFX-1.25
NOPB
3000 units, Tape-and-Reel
LM3671MF-1.25
1000 units, Tape-and-Reel
LM3671MFX-1.25
3000 units, Tape-and-Reel
1.375
LM3671MF-1.375
NOPB
SEDB
1000 units, Tape-and-Reel
LM3671MFX-1.375
NOPB
3000 units, Tape-and-Reel
LM3671MF-1.375
1000 units, Tape-and-Reel
LM3671MFX-1.375
3000 units, Tape-and-Reel
1.5
LM3671MF-1.5
NOPB
SBRB
1000 units, Tape-and-Reel
LM3671MFX-1.5
NOPB
3000 units, Tape-and-Reel
LM3671MF-1.5
1000 units, Tape-and-Reel
LM3671MFX-1.5
3000 units, Tape-and-Reel
1.6
LM3671MF-1.6
NOPB
SDUB
1000 units, Tape-and-Reel
LM3671MFX-1.6
NOPB
3000 units, Tape-and-Reel
LM3671MF-1.6
1000 units, Tape-and-Reel
LM3671MFX-1.6
3000 units, Tape-and-Reel
1.8
LM3671MF-1.8
NOPB
SBSB
1000 units, Tape-and-Reel
LM3671MFX-1.8
NOPB
3000 units, Tape-and-Reel
LM3671MF-1.8
1000 units, Tape-and-Reel
LM3671MFX-1.8
3000 units, Tape-and-Reel
1.875
LM3671MF-1.875
NOPB
SDVB
1000 units, Tape-and-Reel
LM3671MFX-1.875
NOPB
3000 units, Tape-and-Reel
LM3671MF-1.875
1000 units, Tape-and-Reel
LM3671MFX-1.875
3000 units, Tape-and-Reel
2.5*
LM3671MF-2.5
NOPB
TBD
1000 units, Tape-and-Reel
LM3671MFX-2.5
NOPB
3000 units, Tape-and-Reel
LM3671MF-2.5
1000 units, Tape-and-Reel
LM3671MFX-2.5
3000 units, Tape-and-Reel
2.8*
LM3671MF-2.8
NOPB
TBD
1000 units, Tape-and-Reel
LM3671MFX-2.8
NOPB
3000 units, Tape-and-Reel
LM3671MF-2.8
1000 units, Tape-and-Reel
LM3671MFX-2.8
3000 units, Tape-and-Reel
3.3*
LM3671MF-3.3
NOPB
TBD
1000 units, Tape-and-Reel
LM3671MFX-3.3
NOPB
3000 units, Tape-and-Reel
LM3671MF-3.3
1000 units, Tape-and-Reel
LM3671MFX-3.3
3000 units, Tape-and-Reel
*Samples available. To be released soon.
LM3671
www.national.com
4
Ordering Information (5-bump Micro SMD)
Voltage Option
Order Number
Spec
Package Marking
Supplied As
ADJ*
LM3671TL-ADJ
NOPB
TBD
1000 units, Tape-and-Reel
LM3671TLX-ADJ
NOPB
3000 units, Tape-and-Reel
LM3671TL-ADJ
1000 units, Tape-and-Reel
LM3671TLX-ADJ
3000 units, Tape-and-Reel
1.2
LM3671TL-1.2
NOPB
C
1000 units, Tape-and-Reel
LM3671TLX-1.2
NOPB
3000 units, Tape-and-Reel
LM3671TL-1.2
1000 units, Tape-and-Reel
LM3671TLX-1.2
3000 units, Tape-and-Reel
1.5
LM3671TL-1.5
NOPB
D
1000 units, Tape-and-Reel
LM3671TLX-1.5
NOPB
3000 units, Tape-and-Reel
LM3671TL-1.5
1000 units, Tape-and-Reel
LM3671TLX-1.5
3000 units, Tape-and-Reel
1.8
LM3671TL-1.8
NOPB
B
1000 units, Tape-and-Reel
LM3671TLX-1.8
NOPB
3000 units, Tape-and-Reel
LM3671TL-1.8
1000 units, Tape-and-Reel
LM3671TLX-1.8
3000 units, Tape-and-Reel
1.875
LM3671TL-1.875
NOPB
S
1000 units, Tape-and-Reel
LM3671TLX-1.875
NOPB
3000 units, Tape-and-Reel
LM3671TL-1.875
1000 units, Tape-and-Reel
LM3671TLX-1.875
3000 units, Tape-and-Reel
2.5*
LM3671TL-2.5
NOPB
TBD
1000 units, Tape-and-Reel
LM3671TLX-2.5
NOPB
3000 units, Tape-and-Reel
LM3671TL-2.5
1000 units, Tape-and-Reel
LM3671TLX-2.5
3000 units, Tape-and-Reel
2.8*
LM3671TL-2.8
NOPB
TBD
1000 units, Tape-and-Reel
LM3671TLX-2.8
NOPB
3000 units, Tape-and-Reel
LM3671TL-2.8
1000 units, Tape-and-Reel
LM3671TLX-2.8
3000 units, Tape-and-Reel
3.3*
LM3671TL-3.3
NOPB
TBD
1000 units, Tape-and-Reel
LM3671TLX-3.3
NOPB
3000 units, Tape-and-Reel
LM3671TL-3.3
1000 units, Tape-and-Reel
LM3671TLX-3.3
3000 units, Tape-and-Reel
*Samples available. To be released soon.
LM3671
www.national.com
5
PDF 
ZIP