LM3679 Datasheet, PDF (1/22 Pages) National Semiconductor (TI) – 3MHz, 350mA Miniature Step-Down DC-DC Converter for Ultra Low Profile Applications (Height < 0.55mm)

LM3679
www.ti.com
SNVS510A – SEPTEMBER 2007 – REVISED FEBRUARY 2008
LM3679 3MHz, 350mA Miniature Step-Down DC-DC Converter for Ultra Low Profile
Applications (Height < 0.55mm)
Check for Samples: LM3679
FEATURES
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•2 16 µA typical quiescent current
• 350 mA maximum load capability
• 3 MHz PWM fixed switching frequency (typ)
• Automatic PFM/PWM mode switching
• Available in 5-bump micro SMD package and
UR package
• Internal synchronous rectification for high
efficiency
• Internal soft start
• 0.01 µA typical shutdown current
• Operates from a single Li-Ion cell battery
• Current overload and Thermal shutdown
protection
• Three external components required for
typical applications
• Low profile solution (0.55mm max height,
includes four external components)
APPLICATIONS
• Mobile phones
• PDAs
• MP3 players
• W-LAN
• Portable Instruments
• Digital still cameras
• Portable Hard disk drives
DESCRIPTION
The LM3679 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 2.5V to 5.5V. It provides up to 350mA load current, over the entire input
voltage range. The LM3679 output voltage can be configured to 1.2V, 1.5V, or 1.8V.
The device offers superior features and performance for mobile 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 ~ 80mA to 350mA 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 low), the device turns off
and reduces battery consumption to 0.01 µA (typ).
The LM3679 is available in a lead-free (No PB) 5-bump micro SMD package, 0.6mm height, and in an ultra thin
0.3mm height UR package. Using the UR package along with specific external components, allows for a low
profile solution size with a max height of 0.55mm. 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. .
TYPICAL APPLICATION CIRCUIT
V_IN
2.5V to 5.5V ^VIN
C_IN
4.7 PF
GND
1
5
LM3679
2
L1: 1.0 PH
SW
EN ₃
4 ^FB
V_OUT
C_OUT
10 PF
Bill of Materials for Low Profile Solution:
CIN = JMK107BJ475K (Taiyo - Yuden)
COUT = JMK107BJ475K (Taiyo - Yuden) x2
Inductor = LQM21PN1R0M (MuRata)
Figure 1. Typical Low Profile Application Circuit (0.55mm max height using LM3679UR)
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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 © 2007–2008, Texas Instruments Incorporated