MICREL MIC4680

MIC4680
Micrel
MIC4680
1A 200kHz SuperSwitcher™ Buck Regulator
Final Information
General Description
Features
The MIC4680 SuperSwitcher™ is an easy-to-use fixed or
adjustable output voltage step-down (buck) switch-mode
voltage regulator. The 200kHz MIC4680 achieves up to 1.3A
of continuous output current over a wide input range in a
8-lead SOP (small outline package).
The MIC4680 is available in 3.3V and 5V fixed output versions or adjustable output down to 1.25V.
The MIC4680 has an input voltage range of 4V to 34V, 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 2µA of standby current.
The MIC4680 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 MIC4680 is available in the 8-lead SOP with a
–40°C to +125°C junction temperature range.
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•
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•
•
•
•
•
•
•
•
SO-8 package with up to 1.3A output current
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 34V operating input voltage range
Less than 2µA typical shutdown-mode current
Up to 90% efficiency
Thermal shutdown
Overcurrent protection
Applications
•
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Simple 1A high-efficiency step-down (buck) regulator
Replacement of TO-220 and TO-263 designs
Efficient preregulator (5V to 2.5V, 12V to 3.3V, etc.)
On-card switching regulators
Positive-to-negative converter (inverting buck-boost)
Simple battery charger
Negative boost converter
Higher output current regulator using external FET
Typical Applications
+6V to +34V
C1
15µF
35V
SHUTDOWN
2
1
ENABLE
MIC4680-3.3BM
IN
SW
SHDN
FB
3.3V/1A
68µH
C2
220µF
16V
4
D1
B260A or
SS26
GND
Power
SOP-8
L1
3
5–8
Fixed Regulator Circuit
+5V to +34V
C1
15µF
35V
SHUTDOWN
ENABLE
Power
SOP-8
2
1
MIC4680BM
IN
SW
SHDN
FB
3
L1
68µH
4
D1
B260A or
SS26
GND
5–8
2.5V/1A
R1
3.01k
C2
220µF
16V
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) 944-0970 • http://www.micrel.com
June 2000
1
MIC4680
MIC4680
Micrel
Ordering Information
Part Number
Voltage
Junction Temp. Range
Package
MIC4680BM
Adjustable
–40°C to +125°C
8-lead SOP
MIC4680-3.3BM
3.3V
–40°C to +125°C
8-lead SOP
MIC4680-5.0BM
5.0V
–40°C to +125°C
8-lead SOP
Pin Configuration
SHDN 1
8 GND
IN 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 +34V 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 output on fixed output voltage versions, or to
1.23V-tap of voltage-divider network for adjustable version.
5–8
GND
MIC4680
Pin Function
Shutdown (Input): Logic low enables regulator. Logic high (>1.6V) shuts
down regulator.
Ground
2
June 2000
MIC4680
Micrel
Absolute Maximum Ratings (Note 1)
Operating Ratings (Note 2)
Supply Voltage (VIN), Note 3 ...................................... +38V
Shutdown Voltage (VSHDN) .......................... –0.3V to +38V
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), Note 4 .......................... +4V to +34V
Junction Temperature (TJ) ...................................... +125°C
Package Thermal Resistance (θJA), Note 6 ............ 63°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
(±1%)
(±2%)
1.217
1.205
1.230
1.243
1.255
V
V
8V ≤ VIN ≤ 34V, 0.1A ≤ ILOAD ≤ 1A, VOUT = 5V
1.193
1.180
1.230
1.267
1.280
V
V
93
97
MIC4680 [Adjustable]
Feedback Voltage
Maximum Duty Cycle
VFB = 1.0V
Output Leakage Current
VIN = 34V, VSHDN = 5V, VSW = 0V
50
500
µA
VIN = 34V, VSHDN = 5V, VSW = –1V
4
20
mA
VFB = 1.5V
7
12
mA
Quiescent Current
%
MIC4680-3.3
Output Voltage
(±1%)
(±3%)
3.266
3.201
3.3
3.333
3.399
V
V
6V ≤ VIN ≤ 34V, 0.1A ≤ ILOAD ≤ 1A
3.168
3.135
3.3
3.432
3.465
V
V
93
97
Maximum Duty Cycle
VFB = 2.5V
Output Leakage Current
VIN = 34V, VSHDN = 5V, VSW = 0V
50
500
µA
VIN = 34V, VSHDN = 5V, VSW = –1V
4
20
mA
VFB = 4.0V
7
12
mA
Quiescent Current
%
MIC4680-5.0
Output Voltage
(±1%)
(±3%)
4.950
4.85
5.0
5.05
5.15
V
V
8V ≤ VIN ≤ 34V, 0.1A ≤ ILOAD ≤ 1A
4.800
4.750
5.0
5.200
5.250
V
V
93
97
Maximum Duty Cycle
VFB = 4.0V
Output Leakage Current
VIN = 34V, VSHDN = 5V, VSW = 0V
50
500
µA
VIN = 34V, VSHDN = 5V, VSW = –1V
4
20
mA
VFB = 6.0V
7
12
mA
Quiescent Current
June 2000
3
%
MIC4680
MIC4680
Parameter
Micrel
Condition
Min
Typ
Max
Units
Frequency Fold Back
30
50
100
kHz
Oscillator Frequency
180
200
220
kHz
1.4
1.8
V
V
1.8
2.5
A
MIC4680/-3.3/-5.0
Saturation Voltage
IOUT = 1A
Short Circuit Current Limit
VFB = 0V, see Test Circuit
Standby Quiescent Current
VSHDN = VIN
1.5
VSHDN = 5V (regulator off)
30
Shutdown Input Logic Level
1.3
regulator off
2
regulator on
Shutdown Input Current
µA
100
1.6
µA
V
1.0
0.8
V
VSHDN = 5V (regulator off)
–10
–0.5
10
µA
VSHDN = 0V (regulator on)
–10
–1.5
10
µA
Thermal Shutdown
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.
°C
Test Circuit
+12V
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
2V
1V
1.6V
GUARANTEED
OFF
TYPICAL
OFF
VIN(max)
Shutodwn Hysteresis
MIC4680
4
June 2000
MIC4680
Micrel
Typical Characteristics
Line Regulation
5.04
100
5.04
5.03
5.02
5.01
5.00
4.99
4.98
4.97
0
5
10 15 20 25 30
INPUT VOLTAGE (V)
5.00
4.98
4.96
35
VIN = 12V
VOUT = 5V
5.02
0
2.5
2.0
1.5
1.0
0.5
0
-50 -25 0 25 50 75 100 125
TEMPERATURE (°C)
6
202
5
201
4
3
2
1
0
1.238
1.236
1.234
1.232
VIN = 12V
VOUT = 5V
IOUT = 1A
1.230
1.228
-50 -25 0 25 50 75 100 125 150
TEMPERATURE (°C)
1.2
1.0
0.8
0.6
0.4
0.2
5V Output
Efficiency
12V Output
Efficiency
80
60
70
90
80
20
10
0
EFFICIENCY (%)
70
30
7V
60
12V
24V
50
40
30
20
10
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4
OUTPUT CURRENT (A)
June 2000
VIN = 12V
VOUT = 5V
ILOAD = 1A
0
-50 -25 0 25 50 75 100 125
TEMPERATURE (°C)
100
40
0
35
1.4
90
24V 6V
5 10 15 20 25 30
SUPPLY VOLTAGE (V)
1.6
1.240
3.3V Output
Efficiency
12V
0
Saturation Voltage
vs. Temperature
SATURATION VOLTAGE (V)
FEEDBACK VOLTAGE (V)
FREQUENCY (kHz)
198
80
50
35
199
196
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
OUTPUT CURRENT (A)
1.242
180
-50 -25 0 25 50 75 100 125
TEMPERATURE (°C)
10 15 20 25 30
INPUT VOLTAGE (V)
200
Feedback Voltage
vs. Temperature
220
5
197
VIN = 12V
Frequency vs.
Temperature
190
0
Frequency vs.
Supply Voltage
FREQUENCY (kHz)
3.0
EFFICIENCY (%)
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4
OUTPUT CURRENT (A)
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4
OUTPUT CURRENT (A)
5
EFFICIENCY (%)
CURRENT (µA)
OUTPUT VOLTAGE (V)
VIN = 12V
VSHDN = VIN
200
40
Current Limit
Characteristic
4.0
210
60
20
Shutdown Current
vs. Temperature
3.5
80
CURRENT (µA)
IOUT = 1.0A
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
5.06
5.05
4.96
Shutdown Current
vs. Input Voltage
Load Regulation
70
60
15V
24V
50
40
30
20
10
0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
OUTPUT CURRENT (A)
MIC4680
MIC4680
Micrel
Safe
Operating Area
1.5
Minimum
Current Limit
1.4
1.3
1.2
Note
OUTPUT CURRENT (A)
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
VOUT = 5V
TA = 60°C
Demonstration
board layout
0.3
0.2
0.1
0
0
5
10
15
20
25
INPUT VOLTAGE (V)
30
35
Note. For increased output current, see “Applications Information:
Increasing the Maximum Output Current” and Figure 3.
Functional Characteristics
VSW (NORMAL)
12V IN, 5V/1A OUT
Switching Frequency Foldback
Load Transient
VOUT
(100mV/div.)
Normal
Operation
Short
Circuit
Operation
5.1V
5V
1A
IOUT
(500mA/div.)
VSW (SHORTED)
12V IN, 0V OUT
200kHz
VIN = 12V
VOUT = 5V
IOUT = 1.0A to 0.1A
0A
60kHz
TIME (100ms/div.)
TIME
Frequency Foldback
The MIC4680 folds the switching frequency back during a hard
short-circuit condition to reduce the energy per cycle and
protect the device.
MIC4680
6
June 2000
MIC4680
Micrel
Bode Plots
The following bode plots show that the MIC4680 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 = 106°
Full-Load Stability
Phase Margin = 114°
L = 68µF
COUT = 220µF
L = 68µF
COUT = 220µF
VIN = 7V
VOUT = 5.0V
IOUT = 0.0A
VIN = 7V
VOUT = 5.0V
IOUT = 1.0A
TIME (100ms/div.)
TIME (100ms/div.)
No-Load Stability
Phase Margin = 117°
Full-Load Stability
Phase Margin = 69°
L = 68µF
COUT = 220µF
L = 68µF
COUT = 220µF
VIN = 12V
VOUT = 5.0V
IOUT = 0.0A
VIN = 12V
VOUT = 5.0V
IOUT = 1.0A
TIME (100ms/div.)
TIME (100ms/div.)
No-Load Stability
Phase Margin = 125°
Full-Load Stability
Phase Margin = 71°
L = 68µF
COUT = 220µF
L = 68µF
COUT = 220µF
VIN = 34V
VOUT = 5.0V
IOUT = 1.0A
VIN = 34V
VOUT = 5.0V
IOUT = 1.0A
TIME (100ms/div.)
June 2000
TIME (100ms/div.)
7
MIC4680
MIC4680
Micrel
Block Diagrams
VIN
IN
SHDN
Internal
Regulator
200kHz
Oscillator
Current
Limit
Thermal
Shutdown
Comparator
VOUT
SW
Driver
Reset
1A
Switch
COUT
FB
Error
Amp
1.23V
Bandgap
Reference
MIC4680-x.x
GND
Fixed Regulator
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
1A
Switch
COUT
R1
FB
Error
Amp
1.23V
Bandgap
Reference
R2
MIC4680 [adj.]
Adjustable Regulator
MIC4680
8
June 2000
MIC4680
Micrel
A higher feedback voltage increases the error amplifier
output voltage. A higher error amplifier voltage (comparator
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 MIC4680 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 MIC4680 is a variable duty cycle switch-mode regulator
with an internal power switch. Refer to the block diagrams.
Supply Voltage
The MIC4680 operates from a +4V to +34V unregulated
input. Highest efficiency operation is from a supply voltage
around +15V. See the efficiency curves.
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 1.5µA when VSHDN = VIN = 12V and 30µA
when VSHDN = 5V. See “Shutdown Input Behavior: Shutdown
Hysteresis.”
Feedback
Fixed-voltage versions of the regulator have an internal
resistive divider from the feedback (FB) pin. Connect FB
directly to the output voltage.
Adjustable versions require an external resistive voltage
divider from the output voltage to ground, center tapped to the
FB pin. See Figure 6b 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.
June 2000
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MIC4680
MIC4680
Micrel
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
MIC4680BM
2
IN
SW
3
FB
4
L1
R1
CIN
SHUTDOWN
ENABLE
VOUT
1
SHDN
 R1 
VOUT = VREF 
+ 1
 R2 
GND
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
68µH 1.5A
1.8V 3.01k 6.49k
2A 60V Schottky
2.5V 3.01k 2.94k
3.3V 3.01k 1.78k
5.0V 3.01k 976Ω
COUT
15µF 35V
AVX TPSE156035R0200
6.0V 3.01k 787Ω
Coiltronics UP2B-680
220µF 10V
B260A Vishay-Diode, Inc.***
or
AVX TPSE227010R0060
or
Sumida CDRH125-680MC**
SS26 General Semiconductor
or
Sumida CDRH124-680MC**
* All resistors 1%
** shielded magnetics for low RFI applications
*** Vishay-Diode, Inc. (805) 446-4800
Figure 1b. Recommended Components for Common Ouput Voltages
MIC4680
10
June 2000
MIC4680
Micrel
Minimum Copper/Maximum Current Method
Using Figure 3, for a given input voltage range, determine the
minimum ground-plane heat-sink area required for the
application’s maximum output current. Figure 3 assumes a
constant die temperature of 75°C above ambient.
Thermal Considerations
The MIC4680 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. The MIC4680 SuperSwitcher is the first dc-to-dc
converter 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 though 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 of the limitation of the maximum output current on any
MIC4680 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.
1.5
OUTPUT CURRENT (I)
8V
Minimum Current Limit = 1.3A
0
5
10
15
20
25
Figure 3. Output Current vs. Ground Plane Area
When designing with the MIC4680, 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 =
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 MIC4680 (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 = MIC4680 junction temperature
PD(IC) = MIC4680 power dissipation
θJC = junction-to-case thermal resistance.
The θJC for the MIC4680’s power-SOP-8 is
approximately 20°C/W. (Also see Figure 1.)
TC = “pin” temperature measurement taken at the
entry point of pins 6 or 7 into the plastic package
PD =
SOP-8
θJA
AM
BIE
TA = 50°C
0.5
AREA (cm2)
There are two methods of determining the minimum ground
plane area required by the MIC4680.
Quick Method
Make sure that MIC4680 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 MIC4680 as possible. The
area maybe disributed 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.
θCA
24V
34V
0
Determining Ground-Plane Heat-Sink Area
θJC
1.0
12V
ground plane
heat sink area
NT
printed circuit board
Figure 2. Power SOP-8 Cross Section
June 2000
11
MIC4680
MIC4680
Micrel
at the ambient temperature (TA) at which TC is
measured.
TA = ambient temperature at which TC is measured.
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 less than 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.”
Increasing the Maximum Output Current
The maximum output current at high input voltages can be
increased for a given board layout. The additional three
MIC4680BM
IN
SW
components shown in Figure 4 will reduce the overall loss in
the MIC4680 by about 20% at high VIN and high IOUT.
Even higher output current can be achieved by using the
MIC4680 to switch an external FET. See Figure 9 for a 5A
supply with current limiting.
Layout Considerations
Layout is very important when designing any switching regulator. Rapidly changing switching 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
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 Figure 6a
though 6e.
3
1N4148 82Ω
SHDN
D1
FB
2.2nF
GND
5 6 7 8
Figure 4. Increasing Maximum Output Current at High Input Voltages
MIC4680BM
2
IN
SW
3
FB
4
L1
VOUT
68µH
COUT
CIN
1
SHDN
Power
SOP-8
D1
GND
R1
Load
VIN
+4V to +34V
R2
5 6 7 8
GND
Figure 5. Critical Traces for Layout
J1
VIN
4V to +34V
C1
15µF
35V
J3
GND
2
OFF
ON
C2
0.1µF
50V
1
U1 MIC4680BM
IN
SW
SHDN
S1
NKK G12AP
FB
GND
SOP-8
5–8
3
J2
VOUT
1A
L1
68µH
R1
3.01k
4
D1
R6
B260A optional
or
1
SS26
2
* C3 can be used to provide additional stability
and improved transient response.
R2
6.49k
3
JP1a
1.8V
4
C3*
optional
R3
2.94k
5
JP1b
2.5V
R4
1.78k
7
JP1c
3.3V
6
8
R5
976Ω
JP1d
5.0V
C4
220µF
10V
C5
0.1µF
50V
J4
GND
Figure 6a. Evaluation Board Schematic Diagram
MIC4680
12
June 2000
MIC4680
Micrel
Printed Circuit Board Layouts
Figure 6d. Bottom-Side Silk Screen
Figure 6b. Top-Side Silk Screen
Figure 6c. Top-Side Copper
Figure 6e. Bottom-Side Copper
Abbreviated Bill of Material (Critical Components)
Reference
C1
C4
Manufacturer
Description
TPSD156M035R0300
ECE-A1HFS470
AVX1
15µF 35V
47µF 50V, 8mm × 11.5mm
1
Panasonic2
TPSD227M010R0150
AVX
220µF 10V
1
Inc.3
Qty
D1
B260A
SS26
Vishay-Diodes,
General Semiconductor
Schottky
1
L1
UP2B-680
CDH115-680MC
CDRH124-680MC
Coiltronics4
Sumida5
Sumida5
68µH, 1.5A, nonshielded
68µH, 1.5A, nonshielded
68µH, 1.5A, shielded
1
U1
MIC4680BM
Micrel Semiconductor6
1A 200kHz power-SO-8 buck regulator
1
1 AVX:
2
Part Number
http://www.avxcorp.com
Panasonic: http://www.maco.panasonic.co.jp/eccd/index.html
3
Vishay-Diodes, Inc., tel: (805) 446-4800, http://www.diodes.com
4
Coiltronics, tel: (561) 241-7876, http://www.coiltronics.com
5
Sumida, tel: (408) 982-9960, http://www.sumida.com
6
Micrel, tel: (408) 944-0800, http://www.micrel.com
June 2000
13
MIC4680
MIC4680
Micrel
Applications Circuits*
For continuously updated circuits using the MIC4680, see Application Hint 37 at www.micrel.com.
2
MIC4680BM
IN
SW
L1
3
100µH
C2
100nF
OFF
ON
1
SHDN
S1
NKK G12AP
FB
4
D1
MMBR140LT3
R7
4.99k
C3
220µF
10V
4
GND
SOP-8
5–8
U2
J2
5V ±2%
800mA ±5%
R4
16.2k
D2
1N4148
5
3
2
R5
221k
LM4041DIM3-1.2
C4
10nF
U3
MIC6211BM5
To Cellular Telephone
C1
22µF
35V
J3
GND
C5
220nF
R1
0.100Ω
D3
1N4148
J1
+34V max.
R2
3.01k
R3
976Ω
R6
10k
J4
GND
Figure 7. Constant Current and Constant Voltage Battery Charger
J1
+12V
2
C4
68µF
20V
C5
33µF
35V
1
U1 MIC4680BM
IN
SW
SHDN
FB
3
33µH
4
C3
0.022µF
50V
D1
ES1B
1A 100V
GND
SOP-8
J2
GND
J3
GND
L1
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
SHUTDOWN
ENABLE
C1
330µF
25V
1
U2
U1 MIC4680BM MIC4417BM4
IN
SW 3
SHDN
FB
GND
SOP-8
5–8
Si4425DY
L1*
4
R1
1k
D1
5A
50µH
C2
220µF
16V
R2
20mΩ
C3
220µF
16V
3.3V/5A
C4
1000pF
R3
1k
1%
R4
1k
1%
* ISAT = 8A
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 for bills of material.
MIC4680
14
June 2000
MIC4680
June 2000
Micrel
15
MIC4680
MIC4680
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. 1849 FORTUNE DRIVE SAN JOSE, CA 95131
TEL
+ 1 (408) 944-0800
FAX
+ 1 (408) 944-0970
WEB
USA
http://www.micrel.com
This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or
other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc.
© 2000 Micrel Incorporated
MIC4680
16
June 2000