MIC3385
8MHz Inductorless Buck Regulator
with LDO Standby Mode
General Description
The Micrel MIC3385 is a high-efficiency inductorless buck
regulator that features a
LOWQ
®
LDO standby mode that
draws only 18µA of quiescent current. The MIC3385
requires no external inductor enabling an ultra-low noise,
small size, and high efficiency solution for portable power
applications.
In PWM mode, the MIC3385 operates with a constant
frequency 8MHz PWM control. Under light load conditions,
such as in system sleep or standby modes, the PWM
switching operation can be disabled to reduce switching
losses. In this light load
LOWQ
®
mode, the LDO maintains
the output voltage and draws only 18µA of quiescent
current. The LDO mode of operation saves battery life
while not introducing spurious noise and high ripple as
experienced with pulse skipping or bursting mode
regulators.
The MIC3385 operates from 2.7V to 5.5V input and
features internal power MOSFETs that can supply up to
600mA output current in PWM mode. It can operate with a
maximum duty cycle of 100% for use in low-dropout
conditions.
The MIC3385 is available in the 14-pin 3mm x 3.5mm
MLF
®
package with a junction operating range from –40°C
to +125°C.
Data sheets and support documentation can be found on
Micrel’s web site at:
Features
•
2.7 to 5.5V supply voltage
•
Light load
LOWQ
®
LDO mode
– 18µA quiescent current
– Low noise, 75µVrms
•
8MHz PWM mode
– Output current to 600mA
– >90% efficiency
– 100% maximum duty cycle
•
Adjustable output voltage option down to 1V
•
Ultra-fast transient response
•
NO external inductor required
•
Enables sub 1mm profile solution
•
Fully integrated MOSFET switches
•
Micropower shutdown
•
Thermal shutdown and current limit protection
®
•
Pb-free 14-pin 3x3.5x0.9mm MLF package
•
–40°C to +125°C junction temperature range
Applications
•
•
•
•
•
•
Slim digital cameras
MP3 players
Portable power applications
Cellular phones
PDAs
USB peripherals
Typical Application
2.5V
OUT
Efficiency
100
90
80
70
60
50
40
30
20
10
0
0
100 200 300 400 500 600
OUTPUT CURRENT (mA)
V
IN
=3.2V
V
IN
=3.6V
V
IN
=4.2V
®
Adjustable Output Buck Regulator with
LOWQ
Mode
LOWQ
is a registered trademark of Micrel, Inc.
MLF and
MicroLeadFrame
are registered trademarks of Amkor Technology, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (
408
) 944-0800 • fax + 1 (408) 474-1000 •
http://www.micrel.com
May 2010
M9999-051310-B
MICREL [ MICREL SEMICONDUCTOR ]
