MIC2245 Datasheet, PDF (1/14 Pages) Micrel Semiconductor – 4MHz PWM Synchronous Buck Regulator with LDO Standby Mode

MIC2245
4MHz PWM Synchronous Buck
Regulator with LDO Standby Mode
General Description
The Micrel MIC2245 is a high efficiency 4MHz pulse
width modulated (PWM) synchronous buck (step-
down) regulator that features a LOWQ™ LDO
standby mode that draws only 18µA of quiescent
current. The MIC2245 allows an ultra-low noise,
small size, and high efficiency solution for portable
power applications.
In PWM mode, the MIC2245 operates with a
constant frequency 4MHz 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 MIC2245 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 MIC2245 is available in the 10-pin 3mm x 3mm
MLF™ package with a junction operating range from
–40°C to +125°C.
Data sheet 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
• 4MHz PWM mode
Output current to 500mA
>92% efficiency
100% maximum duty cycle
• Adjustable output voltage option down to 1V
Fixed output voltage options available
• Ultra-fast transient response
• Uses a tiny 1µH inductor
• Fully integrated MOSFET switches
• Micropower shutdown operation
• 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
100
90
80
70
60
50
40
30
20
10
00
1.8V_OUT Efficiency
V_IN=3.2V
V_IN=3.6V
V_IN=4.2V
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