MIC4685
Micrel
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
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 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.
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
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
Applications
Ordering Information
Part Number
MIC4685BR
Voltage
Adj
Junction Temperature Range
–40°C to +125°C
Package
SPAK-07L
Typical Applications
V
IN
8V to 30V
V
IN
5V
±10%
D
BS
3A, 20V
C
BS
0.33µF/50V
1
6
3
2
5
MIC4685BR
IN
BS
EN
SW
FB
GND
4, Tab
1
6
3
C
BS
0.33µF/50V
L1
39µH
D1
3A
40V
R1
3.01k
R2
6.49k
2
5
V
OUT
1.8V/3A
C
OUT
330µF
6.3V
C
IN
68µF
10V
MIC4685BR
IN
BS
EN
SW
FB
GND
4, Tab
L1
39µH
D1
3A
20V
R1
3.01k
R2
1.78k
V
OUT
3.3V/2A
330µF
6.3V
C
IN
33µF
35V
1.8V Output Converter
5V to 3.3V Converter
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
September 2002
1
MIC4685
MICREL [ MICREL SEMICONDUCTOR ]
