1

2

5

4

3

SW

FB

EN

GND

L1: 1.0 PH

10 PF

4.7 PF

LM3679

2.5V to 5.5V

Bill of Materials for Low Profile Solution:

CIN

= JMK107BJ475K (Taiyo - Yuden)

COUT

= JMK107BJ475K (Taiyo - Yuden) x2

Inductor = LQM21PN1R0M (MuRata)

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

1

FEATURES

2

•

16 µA typical quiescent current

•

Three external components required for

typical applications

•

350 mA maximum load capability

•

Low profile solution (0.55mm max height,

•

3 MHz PWM fixed switching frequency (typ)

includes four external components)

•

Automatic PFM/PWM mode switching

•

Available in 5-bump micro SMD package and

APPLICATIONS

UR package

•

Mobile phones

•

Internal synchronous rectification for high

•

PDAs

efficiency

•

MP3 players

•

Internal soft start

•

W-LAN

•

0.01 µA typical shutdown current

•

Portable Instruments

•

Operates from a single Li-Ion cell battery

•

Digital still cameras

•

Current overload and Thermal shutdown

•

Portable Hard disk drives

protection

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

Figure 1. Typical Low Profile Application Circuit (0.55mm max height using LM3679UR)

1

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

2

All trademarks are the property of their respective owners.

PRODUCTION DATA information is current as of publication date.

Copyright © 2007–2008, Texas Instruments Incorporated

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.