MIC2285A
8MHz PWM Synchronous Buck Regulator
with LDO Standby Mode
General Description
The Micrel MIC2285A is a high efficiency 8MHz
PWM synchronous buck (step-down) regulator that
features a LOWQ
®
LDO standby mode that draws
only 20µA of quiescent current. The MIC2285A
allows an ultra-low noise, small size, and high
efficiency solution for portable power applications.
In PWM mode, the MIC2285A 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 MIC2285A 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 MIC2285A is available in the 10-pin 2mm x
2mm Thin 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: www.micrel.com.
Features
•
2.7 to 5.5V supply/input voltage
•
Light load LOWQ
®
LDO mode
– 20µA 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
– Fixed output voltage options available
•
Ultra-fast transient response
•
Requires only a 0.47µH inductor
•
Enables sub 0.55mm profile solution
•
Fully integrated MOSFET switches
•
Micropower shutdown
•
Thermal shutdown and current limit protection
•
10-pin 2mm x 2mm x 0.55mm MLF
®
package
•
–40°C to +125°C junction temperature range
Applications
•
Cellular phones
•
PDAs
•
USB peripherals
____________________________________________________________________________________________________
Typical Application
2.5V
OUT
Efficiency
100
90
80
70
60
50
40
30
20
V
IN
=3.2V
V
IN
=3.6V
V
IN
=4.2V
Adjustable Output Buck Regulator with LOWQ Mode
®
10
0
0
100 200 300 400 500 600
OUTPUT CURRENT (mA)
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
August 2007
M9999-083107-B
MICREL [ MICREL SEMICONDUCTOR ]
