MIC4681
Micrel
MIC4681
2A-Peak SuperSwitcher™ SOP-8 Buck Regulator
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 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
Output adjustable down to 1.25V
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
+5V to +30V
C1
22µF
35V
SHUTDOWN
ENABLE
2
MIC4681BM
IN
SW
3
L1
68µH
R1
3.01k
R2
2.94k
2.5V/1A
C2
220µF
10V
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) 474-1000 • http://www.micrel.com
April 2005
1
MIC4681
MIC4681
Micrel
Ordering Information
Part Number
Standard
MIC4681BM
Lead-Free
MIC4681YM
Voltage
Adjustable
Frequency
400kHz
Junction Temp. Range
–40°C to +125°C
Package
8-lead SOP
Pin Configuration
SHDN 1
VIN 2
SW 3
FB 4
8 GND
7 GND
6 GND
5 GND
SOP-8 (M)
Pin Description
Pin Number
1
2
3
4
5–8
Pin Name
SHDN
VIN
SW
FB
GND
Pin Function
Shutdown (Input): Logic low enables regulator. Logic high (>2V) shuts down
regulator.
Supply Voltage (Input): Unregulated +4V to +30V supply voltage.
Switch (Output): Emitter of NPN output switch. Connect to external storage
inductor and Shottky diode.
Feedback (Input): Connect to 1.23V-tap of voltage-divider network
Ground
MIC4681
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April 2005
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
Feedback Voltage
Condition
(±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
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.
Min
1.217
1.205
1.193
1.180
93
Typ
1.230
1.230
95
50
4
7
50
Max
1.243
1.255
1.267
1.280
Units
V
V
V
V
%
µA
mA
mA
kHz
kHz
V
A
µA
µA
V
500
20
12
110
220
1.8
4.5
100
V
FB
= 1.5V
180
200
1.4
2.2
3.4
35
6
2
1.4
1.25
0.8
1
1
V
µA
µA
°C
–10
–10
–0.5
–1.5
160
April 2005
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MIC4681
MIC4681
Micrel
Test Circuit
+30V
Device Under Test
2
3
68µH
IN
SW
SHUTDOWN
ENABLE
1
SHDN
GND
SOP-8
5–8
FB
4
I
Current Limit Test Circuit
Shutdown Input Behavior
OFF
ON
GUARANTEED
ON
TYPICAL
ON
0.8V
1.25V
1.4V
2V
GUARANTEED
OFF
TYPICAL
OFF
0V
V
IN(max)
Shutdown Hysteresis
MIC4681
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April 2005
MIC4681
Micrel
Typical Characteristics
Line Regulation
5.05
OUTPUT VOLTAGE (V)
5.03
5.01
4.99
4.97
4.95
0
Amb = 25°C
10 15 20 25 30
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
Load Regulation
5.05
5.03
5.01
4.99
4.97
4.95
0
SHUTDOWN CURRENT (µA)
Shutdown Current
vs. Input Voltage
100
90
80
70
60
50
40
30
20
10
0
0
5
Amb = 25°C
V
IN
= 12V
0.5
1.0
1.5
OUTPUT CURRENT (A)
2.0
V
SHDN
= 5V
Amb = 25°C
10 15 20 25 30
INPUT VOLTAGE (V)
35
5
Shutdown Current
vs. Input Voltage
14
SHUTDOWN CURRENT (µA)
12
10
8
6
4
2
0
0
5
V
SHDN
= V
IN
Amb = 25°C
10 15 20 25 30
INPUT VOLTAGE (V)
35
SHUTDOWN CURRENT (µA)
Shutdown Current
vs. Temperature
6.6
OUTPUT VOLTAGE (V)
Current Limit
Characteristics
6
5
4
3
2
1 V = 12V
IN
Amb = 25°C
0
0
0.5
1
1.5
2
2.5
OUTPUT CURRENT (A)
V
IN
= 12V
V
SHDN
= V
IN
6.4
6.2
6
5.8
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
3
MIC4681BM Frequency
vs. Supply Voltage
205
215
FREQUENCY (KHz)
Frequency
vs. Temperature
210
205
200
195
190
185
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
FEEDBACK VOLTAGE (V)
VIN = 12V
1.238
1.236
1.234
1.232
1.230
1.228
1.226
1.224
Feedback Voltage
vs. Temperature
FREQUENCY (KHz)
203
201
199
197
195
0
I
OUT
= 100mA
Amb = 25°C
5 10 15 20 25 30 35
INPUT VOLTAGE (V)
V
IN
= 12V
1.222
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
MIC4681 3.3V Output
Efficiency
80
12Vin
24Vin
6Vin
EFFICIENCY (%)
100
80
60
40
20
Amb = 25°C
0
0
0.5
1
1.5
2
OUTPUT CURRENT (A)
2.5
0
0
5V Output Efficiency
100
12V Output Efficiency
15Vin
24Vin
60
40
20
12Vin
7Vin
24Vin
EFFICIENCY (%)
EFFICIENCY (%)
60
80
40
20
Amb = 25°C
0.5
1.0
1.5
2.0
OUTPUT CURRENT (A)
0
0
Amb = 25°C
0.5
1
OUTPUT CURRENT (A)
1.5
April 2005
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MIC4681
