LM3677_0810 Datasheet, PDF (1/24 Pages) National Semiconductor (TI) – 3MHz, 600mA Miniature Step-Down DC-DC Converter for Ultra Low Voltage Circuits

October 28, 2008
LM3677
3MHz, 600mA Miniature Step-Down DC-DC Converter for
Ultra Low Voltage Circuits
General Description
The LM3677 step-down DC-DC converter is optimized for
powering ultra-low voltage circuits from a single Li-Ion cell
battery and input voltage rails from 2.7V to 5.5V. It provides
up to 600 mA load current over the entire input voltage range.
The LM3677 is configured to different fixed voltage output
options as well as an adjustable output voltage version range
from 1.2V to 3.3V.
The device offers superior features and performance for mo-
bile phones and similar portable applications with complex
power management systems. Automatic intelligent switching
between PWM low-noise and PFM low-current mode offers
improved system control. During PWM mode operation, the
device operates at a fixed frequency of 3 MHz (typ). PWM
mode drives loads from ~ 80 mA to 600 mA max. Hysteretic
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 efficiency. In
shutdown mode (Enable pin pulled down), the device turns
off and reduces battery consumption to 0.01 µA (typ.).
The LM3677 is available in a lead-free (NOPB) 5-bump micro
SMD package and 6-pin LLP package. A switching frequency
of 3 MHz (typ.) allows use of tiny surface-mount components.
Only three external surface-mount components, an inductor
and two ceramic capacitors, are required.
Features
■ ^{16 µA typical quiescent current}
■ ^{600 mA maximum load capability}
■ ^{3 MHz PWM fixed switching frequency (typ.)}
■ ^{Automatic PFM/PWM mode switching}
■ ^{Available in 5-bump micro SMD package and 6-pin LLP}
package
■ ^{Internal synchronous rectification for high efficiency}
■ ^{Internal soft start}
■ ^{0.01 µA typical shutdown current}
■ ^{Operates from a single Li-Ion cell battery}
■ ^{Only three tiny surface-mount external components}
required (solution size less than 20 mm²)
■ ^{Current overload and thermal shutdown protection}
Applications
■ ^{Mobile Phones}
■ ^PDAs
■ ^{MP3 Players}
■ ^W-LAN
■ ^{Portable Instruments}
■ ^{Digital Still Cameras}
■ ^{Portable Hard Disk Drives}
Typical Application Circuits
Efficiency vs. Output Current
(V_OUT = 1.8V)
30008401
FIGURE 1. Typical Application Circuit
30008407
FIGURE 2. Typical Application Circuit - ADJ. Version
© 2008 National Semiconductor Corporation 300084
30008487
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