April 2005

1

MIC4681

MIC4681

Micrel

MIC4681

2A-Peak SuperSwitcher™ SOP-8 Buck Regulator

General Description

The MIC4681 SuperSwitcher™ is an easy-to-use step-down

(buck) voltage-mode switching regulator. The 200kHz

MIC4681 achieves over 1A of continuous output current over

a 4V to 30V input range in an 8-lead SOPpackage . The

MIC4681 features a high 2.1A minimum current limit, making

the device ideal for pulsed current applications such as GSM

and TDMA cell phone battery chargers and power supplies.

The MIC4681 sustains an output of 4.2V/2A within a typical

GSM charging environment.

The MIC4681 has an input voltage range of 4V to 30V, with

excellent line, load, and transient response. The regulator

performs cycle-by-cycle current limiting and thermal shut-

down for protection under fault conditions. In shutdown

mode, the regulator draws less than 6

µA of standby current.

The MIC4681 SuperSwitcher™ regulator requires a mini-

mum number of external components and can operate using

a standard series of inductors and capacitors. Frequency

compensation is provided internally for fast transient re-

sponse and ease of use.

The MIC4681 is available in the 8-lead SOP with a

–40

°C to +125°C junction temperature range.

Typical Applications

SW

L1

68

µH

IN

FB

GND

SHDN

C2

220

µF

10V

R1

3.01k

R2

2.94k

2.5V/1A

MIC4681BM

C1

22

µF

35V

+5V to +30V

SHUTDOWN

ENABLE

Power

SOP-8

5–8

4

3

2

1

D1

B340A or

SS36

Adjustable Regulator Circuit

Features

• SO-8 package with over 1A continuous output current

• Capable of 2A pulse charging for GSM applications

• All surface mount solution

• Only 4 external components required

• Fixed 200kHz operation

• Output adjustable down to 1.25V

• Internally compensated with fast transient response

• Wide 4V to 30V operating input voltage range

• Less than 6

µA typical shutdown-mode current

• Up to 90% efficiency

• Thermal shutdown

• Overcurrent protection

Applications

• Cellular phone battery charger

• Cellular phone power supply

• Simple 1A continuous high-efficiency step-down (buck)

regulator

• Replacement of a TO-220 and TO-263 designs

• Positive-to-negative converter (inverting buck-boost)

• Negative boost converter

• Higher output current regulator using external FET

Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com

SuperSwitcher is a trademark of Micrel, Inc.