MIC4685

Micrel

September 2002

1

MIC4685

MIC4685

3A SPAK SuperSwitcher™ Buck Regulator

Final

General Description

The MIC4685 is a high-efficiency 200kHz stepdown (buck)

switching regulator. Power conversion efficiency of above

85% is easily obtainable for a wide variety of applications.

The MIC4685 achieves 3A of continuous current in the 7-lead

SPAK package.

The thermal performance of the SPAK allows it to replace

SPAK saves board space with a 36% smaller footprint than

TO-263.

High efficiency is maintained over a wide output current range

by utilizing a boost capacitor to increase the voltage available

to saturate the internal power switch. As a result of this high

efficiency, only the ground plane of the PCB is needed for a

heat sink.

The MIC4685 allows for a high degree of safety. It has a wide

input voltage range of 4V to 30V (34V transient), allowing it to

be used in applications where input voltage transients may be

present. Built-in safety features include over-current protec-

tion, frequency-foldback short-circuit protection, and thermal

shutdown.

The MIC4685 is available in an 7-lead SPAK package with a

junction temperature range of –40

°C to +125°C.

Typical Applications

BS

IN

1

6

3

4, Tab

2

5

SW

FB

EN

GND

MIC4685BR

0.33

µF/50V

33

µF

35V

330

µF

6.3V

D1

3A

40V

R1

3.01k

R2

6.49k

L1

39

µH

8V to 30V

1.8V/3A

1.8V Output Converter

Features

• Low 2mm profile SPAK package

• 3A continuous output current

• Wide 4V to 30V input voltage range (34V transient)

• Fixed 200kHz PWM operation

• Over 85% efficiency

• Output voltage adjustable to 1.235V

• All surface mount solution

• Internally compensated with fast transient response

• Over-current protection

• Frequency foldback short-circuit protection

• Thermal shutdown

Applications

• Point of load power supplies

• Simple high-efficiency step-down regulators

• 5V to 3.3V/2A conversion

• 12V to 5V/3.3V/2.5V/1.8V 3A conversion

• Dual-output

±5V conversion

• Base stations

• LCD power supplies

• Battery chargers

Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com

Ordering Information

Part Number

Voltage

Junction Temperature Range

Package

MIC4685BR

Adj

–40

°C to +125°C

SPAK-07L

BS

IN

1

6

3

4, Tab

2

5

SW

FB

EN

GND

3A, 20V

MIC4685BR

0.33

µF/50V

68

µF

10V

330

µF

6.3V

D1

3A

20V

R1

3.01k

R2

1.78k

L1

39

µH

5V

±10%

3.3V/2A

5V to 3.3V Converter