MIC4681
Micrel
MIC4681
2A-Peak SuperSwitcher™ SOP-8 Buck Regulator
Preliminary Information
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 is available in 3.3V and 5V fixed output ver-
sions or adjustable output down to 1.25V.
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 6µA 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.
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
3.3V, 5V, and adjustable output versions
Internally compensated with fast transient response
Wide 4V to 30V operating input voltage range
Less than 6µA 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
Typical Applications
+6V to +30V
C1
15µF
35V
SHUTDOWN
ENABLE
2
MIC4681-3.3BM
IN
SW
3
L1
68µH
3.3V/1A
C2
220µF
16V
1
SHDN
GND
5–8
FB
4
Power
SOP-8
D1
B340A or
SS36
Fixed Regulator Circuit
MIC4681BM
IN
SW
+5V to +30V
C1
15µF
35V
2
3
L1
68µH
R1
3.01k
R2
2.94k
2.5V/1A
C2
220µF
16V
SHUTDOWN
ENABLE
1
SHDN
GND
5–8
FB
4
Power
SOP-8
D1
B340A or
SS36
Adjustable Regulator Circuit
SuperSwitcher is a trademark of Micrel, Inc.
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 2000
1
MIC4681
MIC4681
Micrel
Absolute Maximum Ratings
(Note 1)
Supply Voltage (V
IN
),
Note 3
...................................... +34V
Shutdown Voltage (V
SHDN
) .......................... –0.3V to +34V
Steady-State Output Switch Voltage (V
SW
) .................. –1V
Feedback Voltage [Adjustable] (V
FB
) .......................... +12V
Storage Temperature (T
S
) ....................... –65°C to +150°C
ESD,
Note 5
Operating Ratings
(Note 2)
Supply Voltage (V
IN
) ....................................... +4V to +30V
Junction Temperature (T
J
) ...................................... +125°C
Package Thermal Resistance (θ
JA
),
Note 6............
63°C/W
(θ
JC
),
Note 6 ...........
20°C/W
Electrical Characteristics
V
IN
= 12V; I
LOAD
= 500mA; T
J
= 25°C,
bold
values indicate –40°C
≤
T
J
≤
+125°C,
Note 7;
unless noted.
Parameter
MIC4681 [Adjustable]
Feedback Voltage
(±1%)
(±2%)
8V
≤
V
IN
≤
30V, 0.1A
≤
I
LOAD
≤
1A, V
OUT
= 5V
Maximum Duty Cycle
Output Leakage Current
V
FB
= 1.0V
V
IN
= 30V, V
SHDN
= 5V, V
SW
= 0V
V
IN
= 30V, V
SHDN
= 5V, V
SW
= –1V
Quiescent Current
MIC4681-3.3
Output Voltage
(±1%)
(±3%)
6V
≤
V
IN
≤
30V, 0.1A
≤
I
LOAD
≤
1A
Maximum Duty Cycle
Output Leakage Current
V
FB
= 2.5V
V
IN
= 30V, V
SHDN
= 5V, V
SW
= 0V
V
IN
= 30V, V
SHDN
= 5V, V
SW
= –1V
Quiescent Current
MIC4681-5.0
Output Voltage
(±1%)
(±3%)
8V
≤
V
IN
≤
30V, 0.1A
≤
I
LOAD
≤
1A
Maximum Duty Cycle
Output Leakage Current
V
FB
= 4.0V
V
IN
= 30V, V
SHDN
= 5V, V
SW
= 0V
V
IN
= 30V, V
SHDN
= 5V, V
SW
= –1V
Quiescent Current
V
FB
= 6.0V
4.950
4.85
4.800
4.750
93
5.0
5.0
97
50
4
7
500
20
12
5.05
5.15
5.200
5.250
V
V
V
V
%
µA
mA
mA
V
FB
= 4.0V
3.266
3.201
3.168
3.135
93
3.3
3.3
97
50
4
7
500
20
12
3.333
3.399
3.432
3.465
V
V
V
V
%
µA
mA
mA
V
FB
= 1.5V
1.217
1.205
1.193
1.180
93
1.230
1.230
95
50
4
7
500
20
12
1.243
1.255
1.267
1.280
V
V
V
V
%
µA
mA
mA
Condition
Min
Typ
Max
Units
September 2000
3
MIC4681
MIC4681
Parameter
MIC4681/-3.3/-5.0/Adj.
Frequency Fold Back
Oscillator Frequency
Saturation Voltage
Short Circuit Current Limit
Standby Quiescent Current
I
OUT
= 1A
V
FB
= 0V, see
Test Circuit
V
IN
= 30V
(Note 8)
V
SHDN
= 5V (regulator off)
V
SHDN
= V
IN
Shutdown Input Logic Level
regulator off
regulator on
Shutdown Input Current
V
SHDN
= 5V (regulator off)
V
SHDN
= 0V (regulator on)
Thermal Shutdown @ T
J
Note 1.
Note 2.
Note 3.
Note 4.
Note 5.
Note 6.
Note 7.
Note 8.
Exceeding the absolute maximum rating may damage the device.
The device is not guaranteed to function outside its operating rating.
Absolute maximum rating is intended for voltage transients only, prolonged dc operation is not recommended.
V
IN(min)
= V
OUT
+ 2.5V or 4V whichever is greater.
Devices are ESD sensitive. Handling precautions recommended.
Measured on 1" square of 1 oz. copper FR4 printed circuit board connected to the device ground leads.
Test at T
A
= +85°C, guaranteed by design, and characterized to T
J
= +125°C.
Short circuit protection is guaranteed to 30V max.
Micrel
Condition
Min
Typ
Max
Units
50
180
200
1.4
2.2
3.4
35
6
2
1.4
1.25
–10
–10
–0.5
–1.5
160
110
220
1.8
4.5
100
kHz
kHz
V
A
µA
µA
V
0.8
1
1
V
µA
µA
°C
MIC4681
4
September 2000
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