MIC2285 Datasheet, PDF (1/14 Pages) Micrel Semiconductor – 8MHz PWM Synchronous Buck Regulator with LDO Standby Mode

MIC2285
8MHz PWM Synchronous Buck
Regulator with LDO Standby Mode
General Description
The Micrel MIC2285 is a high efficiency 8MHz pulse
width modulated (PWM) synchronous buck (step-
down) regulator that features a LOWQ™ LDO standby
mode that draws only 18µA of quiescent current. The
MIC2285 allows an ultra-low noise, small size, and
high efficiency solution for portable power applications.
In PWM mode, the MIC2285 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 MIC2285 operates from a 2.7V to 5.5V input
voltage and features internal power MOSFETs that can
supply up to 500mA output current in PWM mode. It
can operate with a maximum duty cycle of 100% for
use in low-dropout conditions.
The MIC2285 is available in the 10-pin 3mm x 3mm
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 500mA
>90% efficiency
100% maximum duty cycle
• Adjustable output voltage option down to 1V
Fixed output voltage options available
• Ultra-fast transient response
• Uses a tiny 0.47µH inductor
• Enables sub 1mm profile solution
• Fully integrated MOSFET switches
• Micropower shutdown
• Thermal shutdown and current limit protection
• Pb-free 10-pin 3mm x 3mm MLF package
• –40°C to +125°C junction temperature range
Applications
• Cellular phones
• PDAs
• USB peripherals
____________________________________________________________________________________________________
Typical Application
Adjustable Output Buck Regulator with LOWQ™ Mode
1.8VOUT Efficiency
100
90 ^VIN=3.2V
80
70
V_IN=3.6V
V_IN=4.2V
60
50
40
30
20
10
00 _{100 200 300 400 500}
OUTPUT CURRENT (mA)
Patent Pending
LOWQ is a trademark of Micrel, Inc
MLF and MicroLeadFrame are trademarks of Amkor Technology, Inc
Micrel, Inc • 2180 Fortune Drive • San Jose, Ca 95131 • USA • tel [phone] • fax [phone] • http://www.micrel.com
January 2006
M9999-012406
www.micrel.com