MIC4685
3A SPAK SuperSwitcher™
Buck Regulator
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-pin SPAK package.
The thermal performance of the SPAK allows it to replace
TO-220s and TO-263s (D
2
PAKs) in many applications.
The 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 protection, frequency-foldback short-circuit
protection, and thermal shutdown.
The MIC4685 is available in a 7-pin SPAK package with a
junction temperature range of –40°C to +125°C.
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
Features
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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
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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
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Typical Application
V
IN
8V to 30V
MIC4685_R
2
5
IN
EN
GND
BS
SW
FB
4, Tab
1
6
3
C
BS
0.33µF/50V
L1
39mH
D1
3A
40V
R1
3.01k
R2
6.49k
V
OUT
1.8V/3A
C
OUT
330µF
6.3V
C
IN
33µF
35V
1.8V Output Converter
SuperSwitcher is a trademark of Micrel, 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 2010
1
M9999-012610