MIC4682
Precision Current Limit SOIC-8
SuperSwitcher™ Buck Regulator
General Description
Features
The MIC4682 is an easy-to-use step-down (buck) switch-
•
Programmable output current limit
mode voltage regulator. It features a programmable
– 10% accuracy over temperature
current limit that allows 10% current limit accuracy over its
•
Wide 4V to 34V operating input voltage range
full operating temperature range. The precision current
•
Fixed 200kHz PWM operation
limit makes the MIC4682 ideal for constant-voltage
•
Power SOIC-8 package allows 2A continuous output
constant-current applications, such as simple battery
current
chargers. The precision current limit also gives designers
the ability to set the maximum output current below the
•
All surface mount solution
saturation current rating of the inductor. This allows the
•
Internally compensated
use of the smallest possible inductors for a given
•
Less than 1µA typical shutdown-mode current
application, saving valuable space and cost.
•
Thermal shutdown protection
The MIC4682 is a very robust device. Its 4V to 34V input
voltage range allows the MIC4682 to safely be used in
applications where voltage transients may be present.
Applications
Additional protection features include cycle-by-cycle
•
Battery chargers
current limiting and over-temperature shutdown. The
•
White LED drivers
MIC4682 is available in a thermally optimized power
SOIC-8 package that allows it to achieve 2A of continuous
•
Constant voltage constant current step-down
output current.
converters
The MIC4682 requires a minimum number of external
•
Simple step-down regulator with precise current limit
components and can operate using a standard series of
•
USB power supplies
inductors. Compensation is provided internally for fast
transient response and ease of use. The MIC4682 is
available in the 8-pin power SOIC with a –40°C to +125°C
junction temperature range.
Data sheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
___________________________________________________________________________________________________________
Typical Application
+7.5V to +34V
C1
10µF
50V
(x2)
MIC4682
5
IN
SW
8
L1
68µH
R1
3.01k
R2
976
5V/1A
6
OUTPUT VOLTAGE (V)
MIC4682 Current Limit
Characteristics
4
SHDN
FB
GND
1
R3
10M ISET
3
R4
16.2k
D1
B240
C2
220µF
10V
5
4
3
2
1
V
IN
= 12V
0
0
0.5
1
1.5
CURRENT LIMIT (A)
2
2, 6, 7
Constant Current/Constant Voltage Li-Ion Battery Charger
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
June 2007
M9999-061507
Micrel, Inc.
MIC4682
Ordering Information
Part Number
Standard
MIC4682BM
Pb-Free
MIC4682YM
Voltage
Adj.
Junction Temp. Range
–40° to +125°C
Package
8-Pin SOIC
Note:
Other Voltage available. Contact Micrel for details.
Pin Configuration
FB 1
GND 2
ISET 3
SHDN 4
8
7
6
5
SW
GND
GND
IN
8-Pin Power SOIC (M)
Pin Description
Pin Number
1
2, 6, 7
3
4
5
8
Pin Name
FB
GND
ISET
SHDN
IN
SW
Pin Function
Feedback (Input): Output voltage sense node. Connect to 1.23V-tap of the
output voltage-divider network.
Ground (Return): Ground.
Current Limit Set (Input): Connect an external resistor to ground to set the
current limit. Do not ground or float this pin.
Shutdown (Input): Logic low (<0.8V) enables regulator. Logic high (>2V) shuts
down regulator.
Supply Voltage (Input): Unregulated +4V to +34V supply voltage.
Switch (Output): Internal power emitter of NPN output switch.
June 2007
2
M9999-061507
Micrel, Inc.
MIC4682
Absolute Maximum Ratings
(1)
Supply Voltage (V
IN
)
(3)
....................................................38V
Shutdown Voltage (V
SHDN
)............................. –0.3V to +38V
Steady-State Output Switch Voltage (V
SW
) ....................–1V
Feedback Voltage (V
FB
) .................................................12V
Current Limit Set Voltage (V
ISET
) ....................... 1.23V to 7V
Ambient Storage Temperature (T
s
) ...........–65°C to +150°C
ESD Rating
(5)
.................................................................. 2kV
Operating Ratings
(2)
Supply Voltage (V
IN
)
(4, 7)
....................................... 4V to 34V
Junction Temperature Range (T
J
)............. –40°C to +125°C
Thermal Resistance Impedance
SOIC (θ
JA
)
(6)
.......................................................63°C/W
SOIC (θ
JC
)
(6)
.......................................................20°C/W
Electrical Characteristics
V
IN
= 12V; I
OUT
= 500mA; R
ISET
= 16.2k (1A current limit); T
J
= 25°C,
bold
values indicate –40°C< T
J
< +125°C, unless noted.
Symbol
V
IN
I
IN
Parameter
Supply Voltage Range
Quiescent Current
Standby Quiescent Current
Condition
Note 4
V
FB
= 1.5V
V
SHDN
= 5V (Regulator off)
V
SHDN
= V
IN
(±1%)
(±2%)
8V
≤
V
IN
≤
34V, 0.1A
≤
I
LOAD
≤
0.8A
Min
4
Typ
7
35
1
Max
34
12
100
1.243
1.255
1.267
1.280
Units
V
mA
µA
µA
V
V
V
V
A
kHz
%
V
µA
mA
V
V
µA
µA
°C
V
FB
Feedback Voltage
1.217
1.205
1.193
1.180
1.230
1.230
1
200
95
1.4
2
2
I
LIM
f
SW
D
MAX
V
SW
I
SW
V
SHDN
I
SHDN
T
J
Notes:
Current Limit Accuracy,
Note 7
Oscillator Frequency
Maximum Duty Cycle
Switch Saturation Voltage
Switch Leakage Current
Shutdown Input Logic Level
Shutdown Input Current
Thermal Shutdown
See Test Circuit, V
OUT
= 3.6V
V
FB
= 1.0V
I
OUT
= 1A
V
IN
= 34V, V
SHDN
= 5V, V
SW
= 0V
V
IN
= 34V, V
SHDN
= 5V, V
SW
= –1V
Regulator Off
Regulator On
V
SHDN
= 5V (Regulator Off)
V
SHDN
= 0V (Regulator On)
0.9
180
93
1.1
220
1.8
100
10
0.8
1
1
2
–10
–10
1.4
1.25
–0.5
–0.5
160
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. Absolute maximum rating is intended for voltage transients only; prolonged DC operation is not recommended.
4. V
IN(MIN)
= VOUT + 2.5V or 4V whichever is greater.
5. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5kΩ in series with 100pF.
6. Measured on 1.5” square of 1oz. copper FR4 printed circuit board connected to the device ground leads.
7. Short circuit protection is guaranteed to V
IN
= 30V max.
June 2007
3
M9999-061507
Micrel, Inc.
MIC4682
Test Circuit
OUTPUT VOLTAGE (V)
V
IN
C1 (x2)
10µF
50V
R3
10M
MIC4682
5
IN
SW
8
L1
68µH
R1
3.01k
R2
V
OUT
C2
220µF
10V
5.0
4
SHDN
ISET
3
FB
GND
1
D1
B240A
3.6
10%
0
0.90
OUTPUT CURRENT (A)
1.10
2, 6, 7
R
ISET
Current Limit Test Circuit
Constant-Current Constant-Voltage Accuracy
Shutdown Input Behavior
OFF
ON
0.8V
0V
1.25V
1.4V
2V
V
IN(max)
Shutdown Hysteresis
June 2007
4
M9999-061507
Micrel, Inc.
MIC4682
Typical Characteristics
T
A
= 25°C unless otherwise noted.
80
70
EFFICIENCY (%)
60
50
40
30
20
10
0
0
V
OUT
= 2.5V
0.4
0.8 1.2 1.6
OUTPUT CURRENT (A)
2
V
IN
= 6V
V
IN
= 12V
V
IN
= 30V
V
IN
= 5V
Efficiency
vs. Output Current
SHORT CIRCUIT CURRENT LIMIT (A)
2
V
IN
= 4V
1.8
V
IN
= 5V
1.6
V
IN
= 24V
V
IN
= 12V
1.4
V
IN
= 30V
1.2
V
IN
= 34V
1
0.8
0.6
0.4 L = 68µH
R3 = 10M
0.2 V
OUT
= 1.0V (Pulsed Load)
0
10 15 20 25 30 35 40 45 50
R
ISET
(kΩ)
2
R
=10k
1.8
ISET
R
ISET
=15.8k
1.6
1.4 R
=20k
ISET
1.2 R
ISET
=25k
1
R
ISET
=30k
0.8
R
ISET
=40k
0.6
R
ISET
=50k
L = 68µH
0.4
R3 = 10M
0.2
V
OUT
~0V (Pulsed Load)
0
4 7 10 13 16 19 22 25 28 31 34
INPUT VOLTAGE (V)
SHORT CIRCUIT CURRENT LIMIT (A)
Current Limit
vs. R
ISET
at T
J
= 125°C
Short Circuit Current Limit
vs. Input Voltageat T
J
= –40°C
2
1.8 R
ISET
=10k
1.6
1.4 R
ISET
=15.8k
1.2
R
ISET
=20k
1
R
ISET
=25k
0.8
R
ISET
=30k
0.6
R
ISET
=40k
L = 68µH
0.4
R
ISET
=50k
R3 = 10M
0.2
V
OUT
~0V (Pulsed Load)
0
4 8 12 16 20 24 28 32
INPUT VOLTAGE (V)
Short Circuit Current Limit
vs. Input Voltageat T
J
= 25°C
CURRENT LIMIT (A)
June 2007
5
M9999-061507
嵌入式系统
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