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.
TheMIC4685achieves3Aofcontinuouscurrentinthe7-lead
SPAK package.
• Low 2mm profile SPAK package
• 3A continuous output current
• Wide 4V to 30V input voltage range (34V transient)
• Fixed 200kHz PWM operation
• 3.3V, 5V, and Adjustable output versions
• 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
The thermal performance of the SPAK allows it to replace
2
TO-220s and TO-263s (D 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.
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
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.
• LCD power supplies
• Battery chargers
The MIC4685 is available in an 7-lead SPAK package with a
junction temperature range of –40°C to +125°C.
Ordering Information
Part Number
Standard
Voltage
Junction Temp. Range
Package
Pb-Free
MIC4685BR
MIC4685YR
Adj.
3.3V
5.0V
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
SPAK-07L
SPAK-07L
SPAK-07L
MIC4685-3.3BR
MIC4685-5.0BR
MIC4685-3.3YR
MIC4685-5.0YR
DBS
3A, 20V
Typical Applications
VIN
5V
±10%
CBS
VIN
8V to 30V
0.33µF/50V
MIC4685-3.3BR
MIC4685BR
CBS
2
5
1
6
3
2
5
1
6
3
0.33µF/50V
IN
BS
SW
FB
VOUT
3.3V/2A
FB
VOUT
1.8V/3A
L1
L1
EN
39µH
R1
39µH
CIN
68µF
10V
CIN
33µF
35V
330µF
6.3V
3.01k
COUT
330µF
6.3V
D1
D1
R2
6.49k
GND
4, Tab
GND
4, Tab
3A
3A
20V
40V
5V to 3.3V Converter
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
March 2005
1
M9999-031805