January 2010 1 M9999-012610
MIC4684 Micrel, Inc.
MIC4684
2A High-Efciency SuperSwitcher™ Buck Regulator
General Description
The MIC4684 is a high-efciency 200kHz stepdown (buck)
switching regulator. Power conversion efciency of above
85% is easily obtainable for a wide variety of applications.
The MIC4684 achieves 2A of continuous current in an 8-lead
SO (small outline) package at 60°C ambient temperature.
High efciency is maintained over a wide output current range
by utilizing a boost capacitor to increase the voltage available
to saturate the internal power switch. As a result of this high
efciency, no external heat sink is required. The MIC4684,
housed in an SO-8, can replace larger TO-220 and TO-263
packages in many applications.
The MIC4684 allows for a high degree of safety. It has a wide
input voltage range of 4V to 30V (34V transient), allowing
it to be used in applications where input voltage transients
may be present. Built-in safety features include over-current
protection, frequency-foldback short-circuit protection, and
thermal shutdown.
The MIC4684 is available in an 8-lead SO package with a
junction temperature range of –40°C to +125°C.
Typical Application
BSVIN
4
1
5
2, 6, 7
3
8
SW
FB
EN
GND
MIC4684BM C
BS
0.33µF/50V
C
IN
33µF
35V
330µF
6.3V
3A
40V
R1
3.01k
R2
3.01k
68µH
V
IN
6.5V to 25V V
OUT
2.5V/1.5A
Adjustable Buck Converter
Features
• SO-8 package with 2A continuous output current
• Over 85% efciency
• Fixed 200kHz PWM operation
• Wide 4V to 30V input voltage range
• Output voltage adjustable to 1.235V
• All surface mount solution
• Internally compensated with fast transient response
• Over-current protection
• Frequency foldback short-circuit protection
• Thermal shutdown
Applications
• Simple high-efciency step-down regulator
• 5V to 3.3V/1.7A converter (60°C ambient)
• 12V to 1.8V/2A converter (60°C ambient)
• On-card switching regulator
• Dual-output ±5V converter
• Battery charger
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
0
20
40
60
80
100
00.5 1 1.5 2
)%(YCNEICIFFE
OUTPUT CURRENT (A)
Efficiency
vs. Output Current
V
OUT
= 1.8V V
OUT
= 2.5V
V
OUT
= 3.3V
V
IN
= 5.0V
Efciency vs. Output Current
Ordering Information
Part Number Voltage Junction Temp. Range Package
Standard Pb-Free
MIC4684BM MIC4684YM Adj -40°C to +125°C SOP-8
SuperSwitcher is a trademark of Micrel, Inc.
Micrel, Inc. MIC4684
January 2010 2 M9999-012610
Pin Description
Pin Number Pin Name Pin Function
1 SW Switch (Output): Emitter of NPN output switch. Connect to external storage
inductor and Shottky diode.
2, 6, 7 GND Ground
3 IN Supply (Input): Unregulated +4V to 30V supply voltage (34V transient)
4 BS Booststrap Voltage Node (External Component): Connect to external boost
capacitor.
5 FB Feedback (Input): Outback voltage feedback to regulator. Connect to output
of supply for xed versions. Connect to 1.23V tap of resistive divider for
adjustable versions.
8 EN Enable (Input): Logic high = enable; logic low = shutdown
Pin Conguration
1SW
GND
VIN
BS
8 EN
GND
GND
FB
7
6
5
2
3
4
8-Pin SOP (M)
Detailed Pin Description
Switch (SW, pin 1)
The switch pin is tied to the emitter of the main internal NPN
transistor. This pin is biased up to the input voltage minus the
VSAT of the main NPN pass element. The emitter is also driven
negative when the output inductor’s magnetic eld collapses
at turn-off. During the OFF time the SW pin is clamped by
the output schottky diode to a –0.5V typically.
Ground (GND, pins 2,6,7)
There are two main areas of concern when it comes to the
ground pin, EMI and ground current. In a buck regulator
or any other non-isolated switching regulator the output
capacitor(s) and diode(s) ground is referenced back to the
switching regulator’s or controller’s ground pin. Any resistance
between these reference points causes an offset voltage/IR
drop proportional to load current and poor load regulation.
This is why its important to keep the output grounds placed
as close as possible to the switching regulator’s ground pin.
To keep radiated EMI to a minimum its necessary to place
the input capacitor ground lead as close as possible to the
switching regulators ground pin.
Input Voltage (VIN, pin 3)
The VIN pin is the collector of the main NPN pass element.
This pin is also connected to the internal regulator. The output
diode or clamping diode should have its cathode as close as
possible to this point to avoid voltage spikes adding to the
voltage across the collector.
Bootstrap (BS, pin 4)
The bootstrap pin in conjunction with the external bootstrap
capacitor provides a bias voltage higher than the input volt-
age to the MIC4684’s main NPN pass element. The bootstrap
capacitor sees the dv/dt of the switching action at the SW
pin as an AC voltage. The bootstrap capacitor then couples
the AC voltage back to the BS pin plus the dc offset of VIN
where it is rectied and used to provide additional drive to
the main switch, in this case a NPN transistor.
This additional drive reduces the NPN’s saturation voltage and
increases efciency, from a VSAT of 1.8V, and 75% efciency
to a VSAT of 0.5V and 88% efciency respectively.
Feedback (FB, pin 5)
The feedback pin is tied to the inverting side of a GM error
amplier. The noninverting side is tied to a 1.235V bandgap
reference. Fixed voltage versions have an internal voltage
divider from the feedback pin. Adjustable versions require an
external resistor voltage divider from the output to ground,
with the center tied to the feedback pin.
Enable (EN, pin 8)
The enable (EN) input is used to turn on the regulator and is
TTL compatible. Note: connect the enable pin to the input if
unused. A logic-high enables the regulator. A logic-low shuts
down the regulator and reduces the stand-by quiescent
input current to typically 150µA. The enable pin has an up-
per threshold of 2.0V minimum and lower threshold of 0.8V
maximum. The hysterisis provided by the upper and lower
thresholds acts as an UVLO and prevents unwanted turn on
of the regulator due to noise.
January 2010 3 M9999-012610
MIC4684 Micrel, Inc.
Electrical Characteristics
VIN = VEN = 12V, VOUT = 5V; IOUT = 500mA; TA = 25°C, unless otherwise noted. Bold values indicate –40°C ≤ TJ ≤ +125°C.
Parameter Condition Min Typ Max Units
Feedback Voltage (±2%) 1.210 1.235 1.260 V
(±3%) 1.198 1.272 V
8V ≤ VIN ≤ 30V, 0.1A ≤ ILOAD ≤ 1A, VOUT = 5V 1.186 1.235 1.284 V
1.173 1.297 V
Feedback Bias Current 50 nA
Maximum Duty Cycle VFB = 1.0V 94 %
Output Leakage Current VIN = 30V, VEN = 0V, VSW = 0V 5 500 µA
V
IN = 30V, VEN = 0V, VSW = –1V 1.4 20 mA
Quiescent Current VFB = 1.5V 6 12 mA
Bootstrap Drive Current VFB = 1.5V, VSW = 0V 250 380 mA
Bootstrap Voltage IBS = 10mA, VFB = 1.5V, VSW = 0V 5.5 6.2 V
Frequency Fold Back VFB = 0V 30 50 120 kHz
Oscillator Frequency 180 200 225 kHz
Saturation Voltage IOUT = 1A 0.59 V
Short Circuit Current Limit VFB = 0V, See Test Circuit 2.2 A
Shutdown Current VEN = 0V 150 µA
Enable Input Logic Level regulator on 2 V
regulator off 0.8 V
Enable Pin Input Current VEN = 0V (regulator off) 16 50 µA
V
EN = 12V (regulator on) –1 –0.83 mA
Thermal Shutdown @ TJ 160 °C
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. Devices are ESD sensitive. Handling precautions recommended.
Note 4. 2.5V of headroom is required between VIN and VOUT. The headroom can be reduced by implementing a feed-forward diode a seen on the 5V
to 3.3V circuit on page 1.
Note 5. Measured on 1” square of 1 oz. copper FR4 printed circuit board connected to the device ground leads.
Absolute Maximum Ratings (Note 1)
Supply Voltage (VIN), Note 3 ....................................... +34V
Enable Voltage (VEN)......................................–0.3V to +VIN
Steady-State Output Switch Voltage (VSW) .........–1V to VIN
Feedback Voltage (VFB) .............................................. +12V
Storage Temperature (TS) ........................ –65°C to +150°C
ESD Rating ............................................................... Note 3
Operating Ratings (Note 2)
Supply Voltage (VIN) Note 4 ............................ +4V to +30V
Ambient Temperature (TA) .......................... –40°C to +85°C
Junction Temperature (TJ) ........................ –40°C to +125°C
Package Thermal Resistance
θJA, Note 5 .......................................................... 75°C/W
θ
JC, Note 5 .......................................................... 25°C/W
Micrel, Inc. MIC4684
January 2010 4 M9999-012610
Test Circuit
SW
68µH
I
VIN
BS
FB
EN
Device Under Test
+12V
SOP-8 5
GND
2,6,7
4
13
8
Current Limit Test Circuit
Shutdown Input Behavior
ON
OFF
GUARANTEED
ON
TYPICAL
ON
GUARANTEED
OFF
TYPICAL
OFF
0.8V
1.25V0V 1.4V V
IN(max)
2V
Enable Hysteresis
January 2010 5 M9999-012610
MIC4684 Micrel, Inc.
Typical Characteristics
(TA = 25°C unless otherwise noted)
0
10
20
30
40
50
60
70
80
90
100
00.5 11.5 22.5 3
EFFICIENCY (%)
OUTPUT CURRENT (A)
with Feed Forward Diode
5VOUT
1.8VOUT
2.5VOUT
3.3VOUT
VIN =12V
Efficiency vs. Output Current
0
50
100
150
200
250
300
350
0 10 12 14 16 18 20
BOOTSTRAP CURRENT (mA)
INPUT VOLTAGE (V)
Bootstrap Drive Current
vs. Input Voltage
VIN =12V
VFB =1.5V
2 4 6 8
10.3
10.4
10.5
10.6
10.7
10.8
10.9
0 10 15 20 25 30 35 40
DUTY CYCLE (%)
INPUT VOLTAGE (V)
Minimum Duty Cycle
vs. Input Voltage
VIN =12V
VOUT =5V
V
FB
=1.3V
5
1.225
1.230
1.235
1.240
1.245
1.250
1.255
0 10 15 20 25 30 35 40
REFERENCE VOLTAGE (V)
INPUT VOLTAGE (V)
Reference Voltage
vs. Input Voltage
VIN =12V
VOUT =VREF
IOUT = 500mA
5
0
1
2
3
4
5
6
7
0 10 15 20 25 30
BOOTSTRAP VOLTAGE (V)
INPUT VOLTAGE (V)
Bootstrap Voltage
vs. Input Voltage
VIN =12V
VFB =1.5V
5
0
20
40
60
80
100
120
140
160
180
200
10 15 20 25 30 35 40
INPUT CURRENT (µA)
INPUT VOLTAGE (V)
Shutdown Current
vs. Input Voltage
VEN =0V
05
570
575
580
585
590
595
600
605
10 15 20 25 30 35 40
SATURATION VOLTAGE (mV)
INPUT VOLTAGE (V)
Saturation Voltage
vs. Input Voltage
IOUT =1A
VOUT =5V
05
48.5
49
49.5
50
50.5
51
51.5
10 15 20 25 30 35 40
FREQUENCY (kHz)
INPUT VOLTAGE (V)
Foldback Frequency
vs. Input Voltage
VFB =0V
05
5.7
5.8
5.9
6
6.1
6.2
6.3
0 10 15 20 25 30 35 40
INPUT CURRENT (mA)
INPUT VOLTAGE (V)
Quiescent Current
vs. Input Voltage
VEN=5V
5
50
55
60
65
70
75
80
85
90
95
100
00.2 0.4 0.6 0.8 11.2 1.4 1.6
EFFICIECNY (%)
OUTPUT CURRENT (A)
5VOUT Efficiency without Feed
Forward Diode
VOUT =5V
VIN =8V
VIN = 12V
VIN = 24V
50
55
60
65
70
75
80
85
90
95
100
00.2 0.4 0.6 0.8 11.2 1.4 1.6
EFFICIECNY (%)
OUTPUT CURRENT (A)
3.3VOUT Efficiency without
Feed Forward Diode
VOUT =3.3V
VIN =8V
VIN = 12V
VIN = 24V
50
55
60
65
70
75
80
85
90
95
100
00.5 11.5 2
EFFICIENCY (%)
OUTPUT CURRENT (A)
5VIN Efficiency with Feed
Forward Diode
VOUT =1.8V
VOUT =2.5V
VOUT =3.3V
VIN =5.0V
Micrel, Inc. MIC4684
January 2010 6 M9999-012610
5.000
5.002
5.004
5.006
5.008
5.010
5.012
5.014
5.016
5.018
5.020
00.2 0.4 0.6 0.8 11.2 1.4
OUTPUT VOLTAGE (V)
OUTPUT CURRENT (A)
Load Regulation
VIN =12V
4.98
4.99
5
5.01
5.02
5.03
5.04
5.05
5.06
5.07
5.08
10 15 20 25 30 35 40
OUTPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Line Regulation
IOUT = 500mA
05
1
1.02
1.04
1.06
1.08
1.1
1.12
1.14
1.16
1.18
1.2
-60
-40
-20
0
20
40
60
80
100
120
140
THRESHOLD TRIP POINTS
TEMPERATURE (°C)
Enable Threshold
vs. Temperature
Upper Threshold
Lower Threshold
VIN =12V
VOUT =5V
IOUT = 100mA
1.200
1.201
1.202
1.203
1.204
1.205
1.206
1.207
1.208
1.209
1.210
-60
-40
-20
0
20
40
60
80
100
120
140
FEEDBACK VOLTAGE (V)
TEMPERATURE (°C)
Feedback Voltage
vs. Temperature
VIN =12V
VOUT =V FB
IOUT = 100mA
-1
0
1
2
3
4
5
6
-50 0 50 100 150 200
OUTPUT VOLTAGE (V)
TEMPERATURE (°C)
Shutdown Hysteresis
vs. Temperature
ON
OFF
January 2010 7 M9999-012610
MIC4684 Micrel, Inc.
0
0.5
1
1.5
2
2.5
0 5 10 15 20 25 30 35
CONTINUOUS OUTPUT CURRENT (A)
INPUT VOL T AGE (V)
Typical 5VOUT SOA with
Standard Configuration
VOUT = 5V
TA = 60°C
TJ = 125°C
TA = 25°C
SOA Measured on the MIC4684 Evaluation Board.
SOA Measured on the MIC4684 Evaluation Board.
SOA measured on the MIC4684 Evaluation Board.
0
0.5
1
1.5
2
2.5
010 15 20
OUTPUT CURRENT (A)
INPUT VOLTAGE (V)
VOUT =2.5V
TA=60°C
TJ=125°C
5
Typical 2.5VOUT SOA with
Feed Forward Diode
SOA measured on the MIC4684 Evaluation Board.
0
0.5
1
1.5
2
2.5
010 15 20
OUTPUT CURRENT (A)
INPUT VOLTAGE (V)
VOUT =1.8V
TA=60°C
TJ=125°C
5
Typical 1.8VOUT SOA with
Feed Forward Diode
Micrel, Inc. MIC4684
January 2010 8 M9999-012610
Functional Characteristics
Switching Frequency Foldback
TIME
Normal
Operation
Short
Circuit
Operation
V
SW
(SHORTED)
12V IN, 0V OUT
V
SW
(NORMAL)
12V IN, 5V/1A OUT
200kHz
70kHz
Frequency Foldback
The MIC4684 folds the switching frequency back during a hard short
circuit condition to reduce the energy per cycle and protect the device.
Load Transient
V
IN
= 12V
V
OUT
= 5V
I
OUT
= 1.0A to 0.1A
TIME (100ms/div.)
I
OUT
(500mA/div.)
V
OUT
(100mV/div.)
5.1V
5V
1A
0A
January 2010 9 M9999-012610
MIC4684 Micrel, Inc.
Block Diagrams
SW
FB
R1
R2
C
OUT
V
IN
IN
V
OUT
MIC4684
Internal
Regulator
Bootstrap
Charger
Enable
200kHz
Oscillator
Thermal
Shutdown
Reset
Current
Limit
Com-
parator
Error
Amp
Driver
1.235V
Bandgap
Reference
V V R1
R2 1
R1 R2 V
V1
V 1.235V
OUT REF
OUT
REF
REF
=+
= -
=
( )
( )
Adjustable Regulator
Functional Description
The MIC4684 is a variable duty cycle switch-mode regula-
tor with an internal power switch. Refer to the above block
diagram.
Supply Voltage
The MIC4684 operates from a +4V to +30V (34V transient)
unregulated input. Highest efciency operation is from a supply
voltage around +12V. See the efciency curves on page 5.
Enable/Shutdown
The enable (EN) input is TTL compatible. Tie the input high
if unused. A logic-high enables the regulator. A logic-low
shuts down the internal regulator which reduces the current
to typically 150µA when VEN = 0V.
Feedback
Fixed-voltage versions of the regulator have an internal resis-
tive 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 Table 1 and Table 2 for recommended resis-
tor values.
Duty Cycle Control
A xed-gain error amplier compares the feedback signal
with a 1.235V bandgap voltage reference. The resulting error
amplier 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 amplier output
voltage. A higher error amplier voltage (comparator invert-
ing 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 MIC4684 uses a voltage-mode control architecture.
Output Switching
When the internal switch is ON, an increasing current ows
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 eld in L1 forces current to ow through fast recovery
diode D1, charging COUT.
Output Capacitor
External output capacitor COUT provides stabilization and
reduces ripple.
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.
Micrel, Inc. MIC4684
January 2010 10 M9999-012610
Applications Information
Adjustable Regulators
Adjustable regulators require a 1.23V feedback signal. Rec-
ommended voltage-divider resistor values for common output
voltages are included in Table 1.
For other voltages, the resistor values can be determined
using the following formulas:
VV
R1
R2
1
R1 R2 V
V
1
V1.235V
OUT REF
OUT
REF
REF
=+
=−
=
Minimum Pulse Width
The minimum duty cycle of the MIC4684 is approximately
10%. See Minimum Duty Cycle Graph. If this input-to-output
voltage characteristic is exceeded, the MIC4684 will skip
cycles to maintain a regulated VOUT.
0
5
10
15
20
25
30
35
40
012345 6
)V(EGATLOVTUPNI.XAM
OUTPUT VOLTAGE (V)
Max. V
IN
for a Given V
OUT
for
Constant-Frequency Switchin
g
Figure 1. Minimum Pulse Width Characteristic
Thermal Considerations
The MIC4684 SuperSwitcher™ features the power-SOP-8.
This package has a standard 8-lead small-outline package
prole, but with much higher power dissipation than a standard
SOP-8. Micrel’s MIC4684 SuperSwitcher™ family are the rst
dc-to-dc converters to take full advantage of this package.
The reason that the power SOP-8 has higher power dissipa-
tion (lower thermal resistance) is that pins 2, 6, and 7 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 signicantly 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 MIC4684
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
θ
CA = case-to-ambient thermal resistance
θJC is a relatively constant 25°C/W for a power SOP-8.
θCA is dependent on layout and is primarily governed by the
connection of pins 2, 6, and 7 to the ground plane. The pur-
pose of the ground plane is to function as a heat sink.
θJA is ideally 75°C/W, but will vary depending on the size of
the ground plane to which the power SOP-8 is attached.
Determining Ground-Plane Heat-Sink Area
Make sure that MIC4684 pins 2, 6, and 7 are connected to
a ground plane with a minimum area of 6cm2. This ground
plane should be as close to the MIC4684 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 2, 6, and 7. This ground plane area is more than suf-
cient for most designs.
θJA
θJC θCA
AMBIENT
printed circuit board
ground plane
heat sink area
SOP-8
Figure 2. Power SOP-8 Cross Section
When designing with the MIC4684, it is a good practice to
connect pins 2, 6, and 7 to the largest ground plane that is
practical for the specic design.
Checking the Maximum Junction Temperature:
For this example, with an output power (POUT) of 5W, (5V
output at 1A with VIN = 12V) and 60°C maximum ambient
temperature, what is the junction temperature?
Referring to the “Typical Characteristics: 5V Output Efciency”
graph, read the efciency (η) for 1A output current at VIN =
12V or perform you own measurement.
η = 84%
The efciency is used to determine how much of the output
power (POUT) is dissipated in the regulator circuit (PD).
P=
P
P
D
OUT
OUT
η−
P=
5W
0.84
5W
D−
P
D = 0.95W
January 2010 11 M9999-012610
MIC4684 Micrel, Inc.
A worst-case rule of thumb is to assume that 80% of the total
output power dissipation is in the MIC4684 (PD(IC)) and 20%
is in the diode-inductor-capacitor circuit.
P
D(IC) = 0.8 PD
P
D(IC) = 0.8 × 0.95W
P
D(IC) = 0.76W
Calculate the worst-case junction temperature:
T
J = PD(IC)
θJC + (TC – TA) + TA(max)
where:
T
J = MIC4684 junction temperature
P
D(IC) = MIC4684 power dissipation
θJC = junction-to-case thermal resistance.
The θJC for the MIC4684’s power-SOP-8 is approximately
25°C/W.
T
C = “pin” temperature measurement taken at the
entry point of pins 2, 6 or 7
T
A = ambient temperature
T
A(max) = maximum ambient operating temperature
for the specic design.
Calculating the maximum junction temperature given a
maximum ambient temperature of 60°C:
T
J = 0.76 × 25°C/W + (41°C – 25°C) + 60°C
T
J = 95°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 Charac-
teristics. Also see SOA curves on pages 7 through 8.
Layout Considerations
Layout is very important when designing any switching regu-
lator. 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 as short as possible. For example, keep D1 close
to pin 1 and pins 2, 6, and 7, keep L1 away from sensitive
node FB, and keep CIN close to pin 3 and pins 2, 6, and 7.
See Applications Information: Thermal Considerations for
ground plane layout.
The feedback pin should be kept as far way from the switch-
ing elements (usually L1 and D1) as possible.
A circuit with sample layouts are provided. See Figure 7.
Gerber les are available upon request.
Feed Forward Diode
The FF diode (feed forward) provides an external bias source
directly to the main pass element, this reduces VSAT thus
allowing the MIC4684 to be used in very low head-room ap-
plications I.E. 5VIN to 3.3VOUT.
Load
BS L1
68µH
IN
FB
GND
COUT
R1
R2
D1
VOUT
MIC4684BM
GND
CIN
VIN
+4V to +30V
(34V transient)
Power
SOP-8 267
5
43
SWEN 18
Figure 5. Critical Traces for Layout
Micrel, Inc. MIC4684
January 2010 12 M9999-012610
VIN = 4V to 16V (in feed-forward conguration)
V
OUT I
OUT R1 R2 VIN C
IN D1 D2 L1 COUT
5.0V 1.6A 3.01k 976kΩ 6.5V–16V 47µF, 20V 2A, 30V 1A, 20V 27µH 120µF, 6.3V
Vishay-Dale Schottky Schottky Sumida Vishay-Dale
595D476X0020D2T SS23 MBRX120 CDH74-270MC 594D127X06R3C2T
3.3V 1.7A 3.01k 1.78k 4.85V–16V 47µF, 20V 2A, 30V 1A, 20V 27µH 220µF, 6.3V
Vishay-Dale Schottky Schottky Sumida Vishay-Dale
595D476X0020D2T SS23 MBRX120 CDH74-270MC 594D227X06R3C2T
2.5V 1.8A 3.01k 2.94k 4.5V–16V 47µF, 20V 2A, 30V 1A, 20V 27µH 330µF, 6.3V
Vishay-Dale Schottky Schottky Sumida Vishay-Dale
595D476X0020D2T SS23 MBRX120 CDH74-270MC 594D337X06R3D2T
1.8V 2A 3.01k 6.49k 4.2V–16V 47µF, 20V 2A, 30V 1A, 20V 27µH 330µF, 6.3V
Vishay-Dale Schottky Schottky Sumida Vishay-Dale
595D476X0020D2T SS23 MBRX120 CDH74-270MC 594D337X06R3D2T
Note 1. This bill of materials assumes the use of feedforward schotty diode from VIN to the bootstrap pin.
Table 1. Recommended Components for Common Ouput Voltages
(VIN = 4V to 16V)
Recommended Components for a Given Output Voltage (Feed-Forward Conguration)
SW
L1
47µH
VIN
FB
GND
EN
D1
B340A
or
SS34
J2
VOUT
2A
J4
GND
U1 MIC4684BM
C2
0.1µF
50V
C1
15µF
35V
J1
VIN
4V to +16V
D2
MBRX120
1A/20V
J3
GND SOP-8 2, 6, 7
5
BS 4
13
8
ON
OFF C4
330µF
6.3V
C3*
optional
C5
0.1µF
50V
C6
0.33µF
50V R1
3.01k
R2
6.49k
JP1a
1.8V
R3
2.94k
R4
1.78k
R5
976Ω
JP1b
2.5V
JP1c
3.3V
JP1d
5.0V
1
2
3
4
5
6
7
8
* C3 can be used to provide additional stability
and improved transient response.
Note: optimized for 5VOUT
Figure 6. 4V - 16V Input Evaluation Board Schematic Diagram
January 2010 13 M9999-012610
MIC4684 Micrel, Inc.
Abbreviated Bill of Material (Critical Components)
Reference Part Number Manufacturer Description Qty
C1 594D156X0035D2T Vishay Sprague(1) 15µF 35V 1
C2, C5 VJ0805Y104KXAAB Vitramon 0.1µF 50V 2
C6 GRM426X7R334K50 Murata 0.33µF, 50V ceramic capacitor
C3 Optional 1800pF, 50V ceramic (1)
C4 594D337X06R3D2T Vishay Sprague(2) 330µF, 6.3V, tantalum 1
D1 B340A Diode Inc(3) Schottky 3A, 40V 1
D2 MBRX120 Micro Com. Components(5) Schottky 1A, 20V 1
L1 CDRH104R-470MC Sumida(4) 47µH, 2.1A ISAT 1
U1 MIC4684BM Micrel, Inc.(6) 1A 200kHz power-SO-8 buck regulator 1
Notes:
1. Vishay Dale, Inc., tel: 1 402-644-4218, http://www.vishay.com
2. Vishay Sprague, Inc., tel: 1 207-490-7256, http://www.vishay.com
3. Diodes Inc, tel: (805) 446-4800, http://www.diodes.com
4. Sumida, tel: (408) 982-9960, http://www.sumida.com
5. Micro Commercial Components, tel: (800) 346-3371
6. Micrel, Inc. tel: (408) 944-0800, http://www.micrel.com
Figure 7a. Bottom Side Copper
Figure 7c. Bottom Side Silk Screen
Figure 7b. Top Side Copper
Figure 7d. Top Side Silk Screen
Printed Circuit Board
Evaluation Board Optimized for Low Input Voltage by using Feed-Forward Diode Conguration (VIN = 4V to 16V)
Micrel, Inc. MIC4684
January 2010 14 M9999-012610
VIN = 4V to 30V
VOUT I
OUT R1 R2 VIN C
IN D1 L1 COUT
5.0V 1.7A 3.01k 976kΩ 8V–30V 33µF, 35V 3A, 40V 68µH 120µF, 6.3V
Vishay-Dale Schotty Sumida Vishay-Dale
595D336X0035R2T SS34 CDRH104R-680MC 594D127X06R3C2T
3.3V 1.5A 3.01k 1.78k 7V–28V 33µF, 35V 3A, 40V 68µH 220µF, 6.3V
Vishay-Dale Schotty Sumida Vishay-Dale
595D336X0035R2T SS34 CDRH104R-680MC 594D227X06R3C2T
2.5V 1.5A 3.01k 2.94k 6.5V–23V 33µF, 35V 3A, 40V 68µH 330µF, 6.3V
Vishay-Dale Schotty Sumida Vishay-Dale
595D336X0035R2T SS334 CDRH104R-680MC 594D337X06R3D2T
1.8V 1.5A 3.01k 6.49k 6V–17V 47µF, 25V 3A, 40V 68µH 330µF, 6.3V
Vishay-Dale Schotty Sumida Vishay-Dale
595D476X0025D2T SS334 CDRH104R-680MC 594D337X06R3D2T
Table 2. Recommended Components for Common Ouput Voltages
(VIN = 4V to 30V)
Recommended Components for a Given Output Voltage (Standard Conguration)
SW
L1
47µH
VIN
FB
GND
EN
D1
B340A
or
SS34
J2
VOUT
2A
J4
GND
U1 MIC4684BM
C2
0.1µF
50V
C1
15µF
35V
J1
V
IN
4V to +30V
(34V transient)
J3
GND
SOP-8 2, 6, 7
5
BS
4
13
8
ON
OFF
C4
330µF
6.3V
C3*
optional
C5
0.1µF
50V
C6
0.33µF
50V R1
3.01k
R2
6.49k
JP1a
1.8V
R3
2.94k
R4
1.78k
R5
976Ω
JP1b
2.5V
JP1c
3.3V
JP1d
5.0V
1
2
3
4
5
6
7
8
* C3 can be used to provide additional stability
and improved transient response.
Note: optimized for 5V
OUT
Figure 8. 4V - 30V Input Evaluation Board Schematic Diagram
January 2010 15 M9999-012610
MIC4684 Micrel, Inc.
Abbreviated Bill of Material (Critical Components)
Reference Part Number Manufacturer Description Qty
C1 594D156X0035D2T Vishay Sprague(1) 15µF 35V 1
C2, C5 VJ0805Y104KXAAB Vitramon 0.1µF 50V 2
C6 GRM426X7R334K50 Murata 0.33µF, 50V ceramic capacitor
C3 Optional 1800pF, 50V ceramic (1)
C4 594D337X06R3D2T Vishay Sprague(2) 330µF, 6.3V, tantalum 1
D1 B340A Diode Inc(3) Schottky 3A 40V 1
L1 CDRH104R-470MC Sumida(4) 47µH, 2.1A ISAT 1
U1 MIC4684BM Micrel, Inc.(5) 1A 200kHz power-SO-8 buck regulator 1
Notes:
1. Vishay Dale, Inc., tel: 1 402-644-4218, http://www.vishay.com
2. Vishay Sprague, Inc., tel: 1 207-490-7256, http://www.vishay.com
3. Diodes Inc, tel: (805) 446-4800, http://www.diodes.com
4. Sumida, tel: (408) 982-9960, http://www.sumida.com
5. Micrel, Inc. tel: (408) 944-0800, http://www.micrel.com
Printed Circuit Board
General Purpose Evaluation Board (VIN = 4V to 30V)
Figure 9a. Bottom Side Copper
Figure 9c. Bottom Side Silk Screen
Figure 9b. Top Side Copper
Figure 9d. Top Side Silk Screen
Micrel, Inc. MIC4684
January 2010 16 M9999-012610
Package Information
8-Lead SOP (M)
MICREL INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
tE l + 1 (408) 944-0800 fa x + 1 (408) 474-1000 w E b http://www.micrel.com
This 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 specications at any time without notication to the customer.
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