MIC4681 DATA SHEET (11/05/2015) DOWNLOAD

MIC4681
Micrel
MIC4681
2A-Peak SuperSwitcher™ SOP-8 Buck Regulator
General Description
Features
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 shutdown for protection under fault conditions. In shutdown
mode, the regulator draws less than 6µA of standby current.
The MIC4681 SuperSwitcher™ regulator requires a minimum number of external components and can operate using
a standard series of inductors and capacitors. Frequency
compensation is provided internally for fast transient response and ease of use.
The MIC4681 is available in the 8-lead SOP with a
–40°C to +125°C junction temperature range.
•
•
•
•
•
•
•
•
•
•
•
•
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
Power
SOP-8
2
1
MIC4681BM
IN
SW
SHDN
FB
3
L1
68µH
4
D1
B340A or
SS36
GND
5–8
2.5V/1A
R1
3.01k
C2
220µF
10V
R2
2.94k
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
Voltage
Frequency
Junction Temp. Range
Package
MIC4681YM
Adjustable
400kHz
–40°C to +125°C
8-lead SOP
Pin Configuration
SHDN 1
8 GND
VIN 2
7 GND
SW 3
6 GND
FB 4
5 GND
SOP-8 (M)
Pin Description
Pin Number
Pin Name
1
SHDN
2
VIN
Supply Voltage (Input): Unregulated +4V to +30V supply voltage.
3
SW
Switch (Output): Emitter of NPN output switch. Connect to external storage
inductor and Shottky diode.
4
FB
Feedback (Input): Connect to 1.23V-tap of voltage-divider network
5–8
GND
MIC4681
Pin Function
Shutdown (Input): Logic low enables regulator. Logic high (>2V) shuts down
regulator.
Ground
2
April 2005
MIC4681
Micrel
Absolute Maximum Ratings (Note 1)
Operating Ratings (Note 2)
Supply Voltage (VIN), Note 3 ...................................... +34V
Shutdown Voltage (VSHDN) .......................... –0.3V to +34V
Steady-State Output Switch Voltage (VSW) .................. –1V
Feedback Voltage [Adjustable] (VFB) .......................... +12V
Storage Temperature (TS) ....................... –65°C to +150°C
ESD, Note 5
Supply Voltage (VIN) ....................................... +4V to +30V
Junction Temperature (TJ) ...................................... +125°C
Package Thermal Resistance (θJA), Note 6 ............ 63°C/W
(θJC), Note 6 ........... 20°C/W
Electrical Characteristics
VIN = 12V; ILOAD = 500mA; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +125°C, Note 7; unless noted.
Parameter
Condition
Min
Typ
Max
Units
Feedback Voltage
(±1%)
(±2%)
1.217
1.205
1.230
1.243
1.255
V
V
8V ≤ VIN ≤ 30V, 0.1A ≤ ILOAD ≤ 1A, VOUT = 5V
1.193
1.180
1.230
1.267
1.280
V
V
93
95
Maximum Duty Cycle
VFB = 1.0V
Output Leakage Current
VIN = 30V, VSHDN = 5V, VSW = 0V
50
500
µA
VIN = 30V, VSHDN = 5V, VSW = –1V
4
20
mA
VFB = 1.5V
7
12
mA
50
110
kHz
200
220
kHz
1.4
1.8
V
3.4
4.5
A
100
µA
Quiescent Current
Frequency Fold Back
Oscillator Frequency
180
%
Saturation Voltage
IOUT = 1A
Short Circuit Current Limit
VFB = 0V, see Test Circuit VIN = 30V (Note 8)
Standby Quiescent Current
VSHDN = 5V (regulator off)
35
VSHDN = VIN
6
µA
1.4
V
Shutdown Input Logic Level
regulator off
2.2
2
regulator on
Shutdown Input Current
0.8
V
VSHDN = 5V (regulator off)
–10
–0.5
1
µA
VSHDN = 0V (regulator on)
–10
–1.5
1
µA
Thermal Shutdown @ TJ
160
Note 1.
Exceeding the absolute maximum rating may damage the device.
Note 2.
The device is not guaranteed to function outside its operating rating.
Note 3.
Absolute maximum rating is intended for voltage transients only, prolonged dc operation is not recommended.
Note 4.
VIN(min) = VOUT + 2.5V or 4V whichever is greater.
Note 5.
Devices are ESD sensitive. Handling precautions recommended.
Note 6.
Measured on 1" square of 1 oz. copper FR4 printed circuit board connected to the device ground leads.
Note 7.
Test at TA = +85°C, guaranteed by design, and characterized to TJ = +125°C.
Note 8.
Short circuit protection is guaranteed to 30V max.
April 2005
1.25
3
°C
MIC4681
MIC4681
Micrel
Test Circuit
+30V
2
SHUTDOWN
ENABLE
1
Device Under Test
3
IN
SW
SHDN
FB
68µH
4
I
GND
SOP-8
5–8
Current Limit Test Circuit
Shutdown Input Behavior
OFF
ON
GUARANTEED
ON
0V
TYPICAL
ON
0.8V
1.25V
2V
1.4V
GUARANTEED
OFF
TYPICAL
OFF
VIN(max)
Shutdown Hysteresis
MIC4681
4
April 2005
MIC4681
Micrel
Typical Characteristics
Line Regulation
Load Regulation
5.03
5.01
4.99
4.97
5.01
4.99
4.97
4.95
0
6.6
SHUTDOWN CURRENT (µA)
10
8
6
4
VSHDN = VIN
Amb = 25°C
5
10 15 20 25 30
INPUT VOLTAGE (V)
5.8
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
35
FREQUENCY (KHz)
FREQUENCY (KHz)
210
201
199
200
195
185
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
EFFICIENCY (%)
EFFICIENCY (%)
6Vin
20
April 2005
3
2
1 V = 12V
IN
Amb = 25°C
0
0
0.5
1
1.5
2
2.5
OUTPUT CURRENT (A)
7Vin
24Vin
40
1.234
1.232
1.230
1.228
1.226
1.224
VIN = 12V
1.222
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
12V Output Efficiency
0
0
15Vin
80
24Vin
60
40
20
20
2.5
3
1.236
12Vin
60
Amb = 25°C
0.5
1
1.5
2
OUTPUT CURRENT (A)
4
100
80
24Vin
35
5
5V Output Efficiency
12Vin
10 15 20 25 30
INPUT VOLTAGE (V)
1.238
100
40
0
0
VIN = 12V
205
MIC4681 3.3V Output
Efficiency
5
Feedback Voltage
vs. Temperature
190
IOUT = 100mA
Amb = 25°C
5 10 15 20 25 30 35
INPUT VOLTAGE (V)
VSHDN = 5V
Amb = 25°C
10
Frequency
vs. Temperature
203
60
30
20
6
VIN = 12V
VSHDN = VIN
6
215
80
40
Current Limit
Characteristics
6.2
205
195
0
60
50
0
0
6.4
MIC4681BM Frequency
vs. Supply Voltage
197
70
2.0
FEEDBACK VOLTAGE (V)
SHUTDOWN CURRENT (µA)
12
0
0
80
Shutdown Current
vs. Temperature
14
2
0.5
1.0
1.5
OUTPUT CURRENT (A)
100
90
OUTPUT VOLTAGE (V)
Shutdown Current
vs. Input Voltage
Amb = 25°C
VIN = 12V
EFFICIENCY (%)
4.95
0
Amb = 25°C
5
10 15 20 25 30
INPUT VOLTAGE (V)
5.03
SHUTDOWN CURRENT (µA)
5.05
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
5.05
Shutdown Current
vs. Input Voltage
Amb = 25°C
0.5
1.0
1.5
2.0
OUTPUT CURRENT (A)
5
0
0
Amb = 25°C
0.5
1
OUTPUT CURRENT (A)
1.5
MIC4681
Micrel
MIC4681
Shutdown Thresholds
vs. Temperature
Saturation Voltage
vs. Output Current
1.5
2
SATURATION VOLTAGE (V)
ENABLE THRESHOLD VOLTAGE (V)
MIC4681
Regulator Off
1.0
Regulator On
0.5
V
IN
= 12V
0.0
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
1.5
1
0.5
V
IN
0
0
6
= 12V
Amb = 25°C
0.5
1
1.5
2
OUTPUT CURRENT (A)
April 2005
MIC4681
Micrel
CONTINUOUS OUTPUT CURRENT (A)
4681BMSOA
SOA 5Vout
4681BM
5Vout
1.8
TA = 25°C
1.6
1.4
1.2
1.0
0.8
0.6
0.4
VOUT = 5V
TA = 60°C
0.2
0
0
5
10 15 20 25 30
INPUT VOLTAGE (V)
35
CONTINUOUS OUTPUT CURRENT (A)
4681BMSOA
SOA 3.3Vout
4681BM
3.3Vout
April 2005
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
0
TA = 25°C
VOUT = 3.3V
TA = 60°C
5
10 15 20 25 30
INPUT VOLTAGE (V)
7
35
MIC4681
MIC4681
Micrel
Functional Characteristics
VSW (NORMAL)
12V IN, 5V/1A OUT
Switching Frequency Foldback
Load Transient
1.5A
IOUT
(1A/div)
Normal
Operation
0A
100mV
VOUT
(100mV/div)
VSW (SHORTED)
12V IN, 0V OUT
200kHz
Short
Circuit
Operation
VIN = 12V
VOUT = 5V
60kHz
TIME
TIME (100µs/div)
Frequency Foldback
The MIC4681 folds the switching frequency back during a hard
short-circuit condition to reduce the energy per cycle and
protect the device.
MIC4681
8
April 2005
MIC4681
Micrel
Bode Plots
The following bode plots show that the MIC4681 is stable over all conditions using a 68µF inductor (L) and a 220µF output
capacitor (COUT). To assure stability, it is a good practice to maintain a phase margin of greater than 35°.
No-Load Stability
Phase Margin = 94°
Full-Load Stability
Phase Margin = 74°
L = 68µF
COUT = 220µF
L = 68µF
COUT = 220µF
VIN = 7V
VOUT = 5.0V
IOUT = 0A
Amb = 22°C
VIN = 7V
VOUT = 5.0V
IOUT = 1.1A
Amb = 22°C
No-Load Stability
Phase Margin = 102°
Full-Load Stability
Phase Margin = 53°
L = 68µF
COUT = 220µF
L = 68µF
COUT = 220µF
VIN = 12V
VOUT = 5.0V
IOUT = 1.4A
Amb = 22°C
VIN = 12V
VOUT = 5.0V
IOUT = 0A
Amb = 22°C
Full-Load Stability
Phase Margin = 59°
No-Load Stability
Phase Margin = 118°
L = 68µF
COUT = 220µF
L = 68µF
COUT = 220µF
VIN = 30V
VOUT = 5.0V
IOUT = 1.1A
Amb = 22°C
VIN = 30V
VOUT = 5.0V
IOUT = 0A
Amb = 22°C
April 2005
9
MIC4681
MIC4681
Micrel
Block Diagrams
VIN
IN
SHDN
 R1 
VOUT = VREF 
+ 1
 R2 
Internal
Regulator
200kHz
Oscillator
Thermal
Shutdown
V

R1 = R2  OUT − 1
 VREF

Current
Limit
VREF = 1.23V
Comparator
VOUT
SW
Driver
Reset
3A
Switch
COUT
R1
FB
Error
Amp
1.23V
Bandgap
Reference
R2
MIC4681 [adj.]
Adjustable Regulator
MIC4681
10
April 2005
MIC4681
Micrel
inverting input) causes the comparator to detect only the
peaks of the sawtooth, reducing the duty cycle of the comparator output. A lower feedback voltage increases the duty
cycle. The MIC4681 uses a voltage-mode control architecture.
Output Switching
When the internal switch is ON, an increasing current flows
from the supply VIN, through external storage inductor L1, to
output capacitor COUT and the load. Energy is stored in the
inductor as the current increases with time.
When the internal switch is turned OFF, the collapse of the
magnetic field in L1 forces current to flow through fast
recovery diode D1, charging COUT.
Output Capacitor
External output capacitor COUT provides stabilization and
reduces ripple. See “Bode Plots” for additional information.
Return Paths
During the ON portion of the cycle, the output capacitor and
load currents return to the supply ground. During the OFF
portion of the cycle, current is being supplied to the output
capacitor and load by storage inductor L1, which means that
D1 is part of the high-current return path.
Functional Description
The MIC4681 is a variable duty cycle switch-mode regulator
with an internal power switch. Refer to the block diagrams.
Supply Voltage
The MIC4681 operates from a +4V to +30V unregulated
input. Highest efficiency operation is from a supply voltage
around +12V. See the efficiency curves on page 6.
Enable/Shutdown
The shutdown (SHDN) input is TTL compatible. Ground the
input if unused. A logic-low enables the regulator. A logichigh shuts down the internal regulator which reduces the
current to typically 35µA when VSHDN = VIN = 12V and 6µA
when VSHDN = 5V. See “Shutdown Input Behavior: Shutdown
Hysteresis.”
Feedback
Require an external resistive voltage divider from the output
voltage to ground, center tapped to the FB pin. See Figure 1b
for recommended resistor values.
Duty Cycle Control
A fixed-gain error amplifier compares the feedback signal
with a 1.23V bandgap voltage reference. The resulting error
amplifier output voltage is compared to a 200kHz sawtooth
waveform to produce a voltage controlled variable duty cycle
output.
A higher feedback voltage increases the error amplifier
output voltage. A higher error amplifier voltage (comparator
Applications Information
Adjustable Regulators
Adjustable regulators require a 1.23V feedback signal. Recommended voltage-divider resistor values for common output voltages are included in Figure 1b.
For other voltages, the resistor values can be determined
using the following formulas:
VIN
MIC4681BM
2
IN
SW
3
FB
4
L1
R1
CIN
SHUTDOWN
ENABLE
VOUT
1
SHDN
GND
 R1 
VOUT = VREF 
+ 1
 R2 
COUT
D1
R2
5–8
V

R1 = R2  OUT − 1
 VREF

Figure 1a. Adjustable Regulator Circuit
VREF = 1.23V
VOUT
R1*
R2*
CIN
D1
L1
3A 40V Schottky
68µH 2.0A
COUT
1.8V 3.01k 6.49k
2.5V 3.01k 2.94k
3.3V 3.01k 1.78k
5.0V 3.01k 976Ω
22µF 35V
Vishay Dale
593D226X035E2T
6.0V 3.01k 787Ω
B340A Vishay-Diode, Inc.***
Coiltronics UP3B-680
or
or
SS36 General Semiconductor Sumida CDRH127-680MC**
220µF 10V
Vishay Dale
594D227X0010D2
* All resistors 1%
** shielded magnetics for low RFI applications
*** Vishay-Diode, Inc. (805) 446-4800
Figure 1b. Recommended Components for Common Ouput Voltages
April 2005
11
MIC4681
MIC4681
Micrel
Minimum Copper/Maximum Current Method
Thermal Considerations
The MIC4681 SuperSwitcher™ features the power-SOP-8.
This package has a standard 8-lead small-outline package
profile, but with much higher power dissipation than a standard SOP-8. Micrel's MIC4681 SuperSwitcher™ family are
the first dc-to-dc converters to take full advantage of this
package.
The reason that the power SOP-8 has higher power dissipation (lower thermal resistance) is that pins 5 through 8 and the
die-attach paddle are a single piece of metal. The die is
attached to the paddle with thermally conductive adhesive.
This provides a low thermal resistance path from the junction
of the die to the ground pins. This design significantly improves package power dissipation by allowing excellent heat
transfer through the ground leads to the printed circuit board.
One limitation of the maximum output current on any MIC4681
design is the junction-to-ambient thermal resistance (θJA) of
the design (package and ground plane).
Examining θJA in more detail:
θJA = (θJC + θCA)
where:
θJC = junction-to-case thermal resistance
θCA = case-to-ambient thermal resistance
θJC is a relatively constant 20°C/W for a power SOP-8.
θCA is dependent on layout and is primarily governed by the
connection of pins 5 though 8 to the ground plane. The
purpose of the ground plane is to function as a heat sink.
θJA is ideally 63°C/W, but will vary depending on the size of
the ground plane to which the power SOP-8 is attached.
CONTINUOUS OUTPUT CURRENT (A)
Using Figure 3, for a given input voltage range, determine the
minimum ground-plane heat-sink area required for the
application’s maximum continuous output current. Figure 3
assumes a constant die temperature of 75°C above ambient.
24V
VIN = 30V
0.5
TA = 50°C
0
0
5
10
15
20
25
When designing with the MIC4681, it is a good practice to
connect pins 5 through 8 to the largest ground plane that is
practical for the specific design.
Checking the Maximum Junction Temperature:
For this example, with an output power (POUT) of 5W, (5V
output at 1A maximum with VIN = 12V) and 65°C maximum
ambient temperature, what is the maximum junction temperature?
Referring to the “Typical Characteristics: 5V Output Efficiency” graph, read the efficiency (η) for 1A output current at
VIN = 12V or perform you own measurement.
η = 79%
The efficiency is used to determine how much of the output
power (POUT) is dissipated in the regulator circuit (PD).
PD =
Quick Method
Make sure that MIC4681 pins 5 though 8 are connected to a
ground plane with a minimum area of 6cm2. This ground
plane should be as close to the MIC4681 as possible. The
area may be distributed in any shape around the package or
on any pcb layer as long as there is good thermal contact to
pins 5 though 8. This ground plane area is more than
sufficient for most designs.
POUT
η
− POUT
5W
− 5W
0.79
PD = 1.33W
A worst-case rule of thumb is to assume that 80% of the total
output power dissipation is in the MIC4681 (PD(IC)) and 20%
is in the diode-inductor-capacitor circuit.
PD(IC) = 0.8 PD
PD(IC) = 0.8 × 1.33W
PD(IC) = 1.064W
Calculate the worst-case junction temperature:
TJ = PD(IC) θJC + (TC – TA) + TA(max)
where:
TJ = MIC4681 junction temperature
PD(IC) = MIC4681 power dissipation
PD =
SOP-8
θJA
AM
BIE
1.0
12V
Figure 3. Output Current vs. Ground Plane Area
There are two methods of determining the minimum ground
plane area required by the MIC4681.
θCA
8V
AREA (cm2)
Determining Ground-Plane Heat-Sink Area
θJC
1.5
ground plane
heat sink area
θJC = junction-to-case thermal resistance.
The θJC for the MIC4681’s power-SOP-8 is approximately
20°C/W.
TC = “pin” temperature measurement taken at the
entry point of pins 6 or 7
NT
printed circuit board
Figure 2. Power SOP-8 Cross Section
MIC4681
12
April 2005
MIC4681
Micrel
TA = ambient temperature
TA(max) = maximum ambient operating temperature
for the specific design.
Calculating the maximum junction temperature given a
maximum ambient temperature of 65°C:
TJ = 1.064 × 20°C/W + (45°C – 25°C) + 65°C
TJ = 106.3°C
This value is within the allowable maximum operating junction temperature of 125°C as listed in “Operating Ratings.”
Typical thermal shutdown is 160°C and is listed in “Electrical
Characteristics.”
Layout Considerations
Layout is very important when designing any switching regulator. Rapidly changing currents through the printed circuit
board traces and stray inductance can generate voltage
transients which can cause problems.
To minimize stray inductance and ground loops, keep trace
lengths, indicated by the heavy lines in Figure 5, as short as
possible. For example, keep D1 close to pin 3 and pins 5
through 8, keep L1 away from sensitive node FB, and keep
MIC4681BM
2
IN
SW
3
FB
4
L1
VOUT
68µH
COUT
CIN
1
SHDN
Power
SOP-8
D1
GND
R1
Load
VIN
+4V to +30V
CIN close to pin 2 and pins 5 though 8. See “Applications
Information: Thermal Considerations” for ground plane layout.
The feedback pin should be kept as far way from the switching
elements (usually L1 and D1) as possible.
A circuit with sample layouts are provided. See Figures 6a
though 6e. Gerber files are available upon request.
R2
5 6 7 8
GND
Figure 5. Critical Traces for Layout
J1
VIN
4V to +30V
C1
22µF
35V
J3
GND
2
C2
0.1µF
50V
OFF
ON
1
U1 MIC4681BM
IN
SW
SHDN
JP1
FB
GND
SOP-8
5–8
3
J2
VOUT
1A
L1
68µH
R1
3.01k
4
D1
R6
B340A optional
or
1
SS36
2
* C3 can be used to provide additional stability
and improved transient response.
R2
6.49k
3
JP2a
1.8V
4
C3* 1800pF / 50V
optional
R3
2.94k
5
JP2b
2.5V
R4
1.78k
7
JP2c
3.3V
6
8
R5
976Ω
JP2d
5.0V
C4
220µF
10V
C5
0.1µF
50V
J4
GND
Figure 6a. Evaluation Board Schematic Diagram
April 2005
13
MIC4681
MIC4681
Micrel
Printed Circuit Board Layouts
Figure 6b. Top-Side Silk Screen
Figure 6d. Bottom-Side Silk Screen
Figure 6c. Top-Side Copper
Figure 6e. Bottom-Side Copper
Abbreviated Bill of Material (Critical Components)
Reference
C1
C4
1
Part Number
593D226X035E2T
594D227X0010D2
Manufacturer
Description
Qty
Vishay
Dale1
22µF / 35V
1
Vishay
Dale1
220µF / 10V
1
Dale1
0.1 / 50V
1
C2,C5
VJ0805Y104KXXMB
Vishay
D1
340A
Diodes Inc.2
Schottky Diode 3A, 40V
1
L1
CDRH127-680MC
Sumida3
68µH, ISAT 2.1A, shielded
1
U1
MIC4681BM
Micrel Semiconductor4
200kHz Super Switcher™SOIC 8 pin
1
Vishay Dale, Inc., tel: 1 877-847-4291, http://www.vishay.com
2
Diodes Inc, tel: (805) 446-4800, http://www.diodes.com
3
Sumida, tel: (408) 982-9960, http://www.sumida.com
4
Micrel, tel: (408) 944-0800, http://www.micrel.com
MIC4681
14
April 2005
MIC4681
Micrel
Applications Circuits*
For continuously updated circuits using the MIC4681, see Application Hint 37 at www.micrel.com.
2
U1 MIC4681
IN
SW
L1
3
100µH
C2
100nF
OFF
ON
1
SHDN
S1
NKK G12AP
FB
4
R7
4.99k
C3
220µF
10V
D1
MMBR140LT3
4
GND
SOP-8
J2
5V ±2%
800mA ±5%
5–8
R4
16.2k
U2
D2
1N4148
5
3
2
R5
221k
LM4041DIM3-1.2
C4
10nF
To Cellular Telephone
C1
22µF
35V
J3
GND
C5
220nF
R1
0.100Ω
D3
1N4148
J1
+30V max.
R2
3.01k
R3
976Ω
U3
MIC6211BM5
R6
10k
J4
GND
Figure 7. Constant Current and Constant Voltage Battery Charger
J1
+12V
2
C4
68µF
20V
C5
33µF
35V
1
U1 MIC4681
IN
SW
SHDN
FB
33µH
C3
0.022µF
50V
4
D1
ES1B
1A 100V
GND
SOP-8
J2
GND
J3
GND
L1
3
5–8
R1
8.87k
C1
68µF
20V
R2
1k
C2
0.1µF
J4
–12V/150mA
Figure 8. +12V to –12V/150mA Buck-Boost Converter
+4.5V to +17V
2
C1
100µF
20V
C6
0.1µF
50V
1
U2
U1 MIC4681 MIC4417BM4
IN
SW 3
SHDN
SHUTDOWN
ENABLE
FB
GND
SOP-8
5–8
Q1
4
R1
1k
1%
* ISAT = 7.5A
Si4425DY
L1*
D1
5A
50µH
C2
470µF
6.3V
R2
20mΩ
C3
470µF
6.3V
3.3V/5A
C4
1000pF
R3
1k
1%
R4
1k
1%
R5
16k
1%
R6
16k 1%
R7
3.01k
1%
D2
1N4148
U3
R8
MIC6211BM5 1.78k
1%
C5
0.1µF
GND
Figure 9. 5V to 3.3V/5A Power Supply
* See Application Hint 37 at www.micrel.com for bills of material.
April 2005
15
MIC4681
MIC4681
Micrel
Package Information
0.026 (0.65)
MAX)
PIN 1
0.157 (3.99)
0.150 (3.81)
DIMENSIONS:
INCHES (MM)
0.020 (0.51)
0.013 (0.33)
0.050 (1.27)
TYP
0.064 (1.63)
0.045 (1.14)
45°
0.0098 (0.249)
0.0040 (0.102)
0.197 (5.0)
0.189 (4.8)
0°–8°
SEATING
PLANE
0.010 (0.25)
0.007 (0.18)
0.050 (1.27)
0.016 (0.40)
0.244 (6.20)
0.228 (5.79)
8-Lead SOP (M)
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131
TEL
+ 1 (408) 944-0800
FAX
+ 1 (408) 474-1000
WEB
USA
http://www.micrel.com
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use.
Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can
reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into
the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s
use or sale of Micrel Products for use in life support appliances, devices or systems is at Purchaser’s own risk and Purchaser agrees to fully indemnify
Micrel for any damages resulting from such use or sale.
© 2005 Micrel, Incorporated.
MIC4681
16
April 2005