MIC2285

8MHz PWM Synchronous Buck

Regulator with LDO Standby Mode

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 +1 (408) 944-0800 • fax +1 (408) 474-1000 • http://www.micrel.com

January 2006

M9999-012406

www.micrel.com

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

0

10

20

30

40

50

60

70

80

90

100

OUTPUT CURRENT (mA)

0

100

200

300

400

500