LM3678 Datasheet, PDF (1/14 Pages) National Semiconductor (TI) – High-Performance, Miniature 1.5A Step-Down DC-DC Converter for Handheld Applications

April 30, 2008
LM3678 High-Performance, Miniature 1.5A Step-Down DC-
DC Converter for Handheld Applications
General 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 2.5V to 5.5V. It provides up to 1.5A
load current, over the entire input voltage range. LM3678 of-
fers a 0.8V/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
3.3MHz. Internal synchronous rectification provides high ef-
ficiency during PWM mode operation. In shutdown mode, the
device turns off and reduces battery consumption to 0.01µA
(typ).
The LM3678 is available in a 3mm x 3mm LLP-10 package.
A high switching frequency of 3.3MHz (typ.) 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, please refer to ordering infor-
mation section or contact National Semiconductor.
Features
■ ^V_OUT ^{= 0.8V/1.2V}
■ ^V_IN ^{= 2.5V to 5.5V}
■ ^{1.5A maximum load capability}
■ ^{3.3MHz PWM fixed switching frequency (typ.) allows the}
use of 1µH inductor
■ ^{+/- 3% DC output voltage precision}
■ ^{0.01µA 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}
Typical Application Circuit
Efficiency vs. Output Current
( V_OUT = 1.2V)
Note: V_SEL H = 1.2V, V_SEL L = 0.8V
FIGURE 1.
20204501
20204504
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