LM3678_14 Datasheet, PDF (1/18 Pages) Texas Instruments – High-Performance Miniature 1.5-A Step-Down DC-DC Converter for Handheld Applications

LM3678
www.ti.com
SNVS464B – APRIL 2008 – REVISED JANUARY 2009
High-Performance Miniature 1.5-A Step-Down DC-DC Converter for Handheld Applications
Check for Samples: LM3678
FEATURES
1
•2 V_OUT = 0.8 V or 1.2 V
• V_IN = 2.5 V to 5.5 V
• 1.5-A Maximum Load Capability
• 3.3-MHz (Typical) PWM Fixed Switching
Frequency Allows Use of 1-µH Inductor
• ±3% DC Output Voltage Precision
• 0.01-µA (Typical) Shutdown Current
• Internal Synchronous Rectification for High
Efficiency
• Internal Soft Start
• Current Overload and Thermal Shutdown
Protection
APPLICATIONS
• PDAs and Smart Phones
• Personal Media Players
• W-LAN
• USB Modem Applications
• Digital Still Cameras
• Portable Hard Disk Drives
DESCRIPTION
The LM3678 step-down DC-DC converter is optimized for powering low-voltage circuits from a single Li-Ion cell
battery and input voltage rails from 2.5 V to 5.5 V. It provides up to 1.5-A load current, over the entire input
voltage range. LM3678 offers a 0.8V or 1.2V option. One of the pair of voltages is set through the VSELECT pin.
LM3678 operates in PWM mode with a fixed frequency of 3.3 MHz. Internal synchronous rectification provides
high efficiency during PWM mode operation. In shutdown mode, the device turns off and reduces battery
consumption to 0.01 µA (typical).
The LM3678 is available in a 3mm x 3mm DSC-10 package. A high switching frequency of 3.3 MHz (typical)
allows use of tiny surface-mount components. Only three external surface-mount components, an inductor and
two ceramic capacitors, are required (solution size less than 33 mm²). For voltages other than the voltage shown,
contact TI or your distributor.
Typical Application Circuit
VIN = 2.5V to 5.5V
CIN 10 PF
VDD
VDD
1 PH
SW
FB
COUT
EN
PWM
LM3678
0.8V/1.2V
VSELECT
GND
PGOOD
GND
VOUT
22 PF
Note: V_SEL H = 1.2V, V_SEL L = 0.8V
Figure 1.
Efficiency vs. Output Current
( V_OUT = 1.2V)
V_IN = 2.5V, 2.7V
90
80
70
60
V_IN = 3.6V
50
40
30
V_IN = 4.5V
20
10
0
V_IN = 5.5V
0.010
0.100
1.000
LOAD (A)
Figure 2.
10.000
1
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2
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2008–2009, Texas Instruments Incorporated