MIC4685-3.3BR [MICROCHIP]
Switching Regulator, Voltage-mode, 1A, 225kHz Switching Freq-Max, PSSO7, SPAK-7;
| 型号： | MIC4685-3.3BR |
| 厂家： | 
MICROCHIP |
| 描述： | Switching Regulator, Voltage-mode, 1A, 225kHz Switching Freq-Max, PSSO7, SPAK-7 开关 |
| 文件： | 总17页 (文件大小：332K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MIC4685
3A SPAK SuperSwitcher™
Buck Regulator
General Description
Features
The MIC4685 is a high-efficiency 200kHz stepdown (buck)
switching regulator. Power conversion efficiency of above
85% is easily obtainable for a wide variety of applications.
The MIC4685 achieves 3A of continuous current in the
7-pin SPAK package.
• Low 2mm profile SPAK package
• 3A continuous output current
• Wide 4V to 30V input voltage range (34V transient)
• Fixed 200kHz PWM operation
• Over 85% efficiency
• Output voltage adjustable to 1.235V
• All surface mount solution
• Internally compensated with fast transient response
• Over-current protection
The thermal performance of the SPAK allows it to replace
TO-220s and TO-263s (D2PAKs) in many applications.
The SPAK saves board space with a 36% smaller footprint
than TO-263.
High-efficiency 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-efficiency, only the ground plane of the PCB is
needed for a heat sink.
• Frequency foldback short-circuit protection
• Thermal shutdown
The MIC4685 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.
Applications
• Point-of-load power supplies
• Simple high-efficiency step-down regulators
• 5V to 3.3V/2A conversion
• 12V to 5V/3.3V/2.5V/1.8V 3A conversion
• Dual-output ±5V conversion
• Base stations
The MIC4685 is available in a 7-pin SPAK package with a
junction temperature range of –40°C to +125°C.
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
• LCD power supplies
• Battery chargers
___________________________________________________________________________________________________________
Typical Application
VIN
8V to 30V
MIC4685_R
CBS
2
5
1
6
3
0.33µF/50V
IN
EN
BS
SW
FB
VOUT
1.8V/3A
L1
R1
3.01k
39mH
CIN
33µF
35V
COUT
330µF
6.3V
D1
R2
6.49k
GND
4, Tab
3A
40V
1.8V Output Converter
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
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Micrel, Inc.
MIC4685
Ordering Information
Part Number
Junction
Temp. Range
Voltage
Package
Standard
RoHS Compliant*
MIC4685BR
MIC4685WR
Adj.
Adj.
–40° to +125°C
7-Pin SPAK
MIC4685WR EV
Evaluation Board
* RoHS compliant with ‘high-melting solder’ exemption.
Pin Configuration
7
NC
SW
EN
GND
FB
6
5
4
3
2
1
IN
BS
7-Pin SPAK (R)
Pin Description
Pin Number
Pin Name
Pin Function
1
BS
Bootstrap Voltage Node (External Component): Connect to external boost
capacitor.
2
3
IN
Supply (Input): Unregulated +4V to 30V supply voltage (34V transient)
FB
Feedback (Input): Outback voltage feedback to regulator. Connect to 1.235V
tap of resistive divider.
4, Tab
GND
EN
Ground
5
6
Enable (Input): Logic high = enable; logic low = shutdown
SW
Switch (Output): Emitter of NPN output switch. Connect to external storage
inductor and Schottky diode.
7
NC
No Connect. Tie this pin-to-ground.
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MIC4685
Bootstrap (BS, Pin 1)
Detailed Pin Description
The bootstrap pin, in conjunction with the external
bootstrap capacitor, provides a bias voltage higher than
the input voltage to the MIC4685’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 rectified and
used to provide additional drive to the main switch; in this
case, a NPN transistor.
Switch (SW, Pin 6)
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 field collapses at turn-off. During the OFF time,
the SW pin is clamped by the output Schottky diode
typically to a –0.5V.
This additional drive reduces the NPN’s saturation voltage
and increases efficiency, from a VSAT of 1.8V, and 75%
Ground (GND, Pin 4, Tab)
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 it’s 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, it is necessary to place the input capacitor
ground lead as close as possible to the switching
regulator’s ground pin.
efficiency to
respectively.
a VSAT of 0.5V and 88% efficiency
Feedback (FB, Pin 3)
The feedback pin is tied to the inverting side of an error
amplifier. The noninverting side is tied to a 1.235V
bandgap reference. An external resistor voltage divider is
required from the output-to-ground, with the center tied to
the feedback pin. See Tables 1 and 2 for recommended
resistor values.
Enable (EN, Pin 5)
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.
Input Voltage (VIN, Pin 2)
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.
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Micrel, Inc.
MIC4685
Absolute Maximum Ratings(1)
Operating Ratings(2)
Supply Voltage (VIN) (1) .................................................+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
EDS Rating(3)..................................................................2kV
Supply Voltage (VIN) (4) ..................................... +4V to +30V
Junction Temperature (TJ) ........................–40°C to +125°C
Package Thermal Resistance
SPAK-7 (θJA)...................................................11.8°C/W
SPAK-7 (θJC).....................................................2.2°C/W
Electrical Characteristics
VIN = VEN = 12V; VOUT 5V; IOUT = 500mA; TA = 25°C, bold values indicate –40°C< TJ < +125°C, unless noted.
Parameter
Condition
Min
Typ
Max
Units
MIC4685 [Adjustable]
Feedback Voltage
(±2%)
(±3%)
1.210
1.198
1.235
1.235
1.260
1.272
V
V
8V ≤ VIN ≤ 30V, 0.1A ≤ ILOAD ≤ 1A, VOUT = 5V, Note 4
1.186
1.173
1.284
1.297
V
V
Feedback Bias Current
Maximum Duty Cycle
Output Leakage Current
50
94
nA
%
VFB = 1.0V
VIN = 30V, VEN = 0V, VSW = 0V
VIN = 30V, VEN = 0V, VSW = 1V
VFB = 1.5V
5
500
20
µA
mA
mA
mA
V
1.4
6
Quiescent Current
12
Bootstrap Drive Current
Bootstrap Voltage
VFB = 1.5V, VSW = 0V
IBS = 10mA, VFB = 1.5V, VSW = 0V
VFB = 0V
250
5.5
30
380
6.2
70
Frequency Fold Back
Oscillator Frequency
Saturation Voltage
120
225
kHz
kHz
V
180
200
0.59
IOUT = 1A
Short Circuit Current Limit
Shutdown Current
VFB = 0V, See Test Circuit
VEN = 0V
3.5
2
6
A
150
200
µA
V
Enable Input Logic Level
regulator on
regulator off
0.8
50
V
Enable Pin Input Current
VEN = 0V (regulator off)
VEN = 0V (regulator on)
16
µA
mA
°C
–1
–0.83
160
Thermal Shutdown @ TJ
Notes:
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5kΩ in series with 100pF.
4. 2.5V of headroom is required between VIN and VOUT. The headroom can be reduced by implementing a bootstrap diode as seen on the 5V to 3.3V
circuit on page 1.
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Micrel, Inc.
MIC4685
Test Circuit
Device Under Test
68µH
+12V
2
5
6
1
VIN
SW
EN
BS
I
GND
FB
4, Tab 3
Current Limit Test Circuit
Shutdown Input Behavior
ON
OFF
0.8V
1.25V
2V
0V
1.4V
VIN(max)
Enable Hysteresis
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MIC4685
Typical Characteristics
(TA = 25°C unless otherwise noted)
Efficiency
vs. Output Current
100
V
IN = 8V
V
IN = 12V
90
80
70
60
50
40
30
20
10
0
VIN = 30V
Standard
Configuration
VOUT = 5.0V
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
OUTPUT CURRENT (A)
Efficiency
vs. Output Current
90
80
70
60
50
40
30
20
10
0
VIN = 8V
VIN = 24V
VIN = 30V
VIN = 12V
Standard
Configuration
VOUT = 1.8V
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
OUTPUT CURRENT (A)
Efficiency
vs. Output Current
Quiescent Current
vs. Input Voltage
90
80
70
60
50
40
30
20
10
0
6.3
6.2
6.1
6
VIN = 5V
VIN = 12V
VIN = 16V
5.9
5.8
5.7
Bootstrap
Configuration
OUT = 1.8V
VEN= 5V
V
0
5
10 15 20 25 30 35 40
INPUT VOLTAGE (V)
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
OUTPUT CURRENT (A)
Minimum Duty Cycle
vs. Input Voltage
Bootstrap Drive Current
vs. Input Voltage
350
300
250
200
150
100
50
12
10
8
6
4
VIN = 12V
VFB = 1.5V
2
VOUT = 1.8V
0
0
0
2 4 6 8 10 12 14 16 18 20
0
5
10 15 20 25 30
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
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MIC4685
Feedback Voltage
vs. Input Voltage
1.250
1.245
1.240
1.235
1.230
1.225
1.220
1.215
1.210
IOUT = 10mA
VOUT = 1.8V
1.205
0
5
10 15 20 25 30
INPUT VOLTAGE (V)
Feedback Voltage
vs. Temperature
1.258
1.248
1.238
1.228
1.218
1.208
1.198
IOUT = 10mA
VIN = 12V
VOUT = 1.8V
-40-20 0 20 40 60 80 100120140
TEMPERATURE°(C)
Enable Threshold
vs. Temperature
1.20
1.18
1.16
1.14
1.12
1.10
1.08
1.06
1.04
1.02
1.00
Upper Threshold
Lower Threshold
VIN = 12V
VOUT = 5V
IOUT = 100mA
TEMPERATURE°(C)
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MIC4685
Typical Safe Operating Area (SOA)
(SOA measured on the MIC4685 Evaluation Board*)
Typical 5V Output SOA
Standard Configuration
Typical 3.3V Output SOA
Typical 2.5V Output SOA
5.0
TA = 25°C
4.5
TJ = 125°C
4.0
D = Max
3.5
3.0
2.5
2.0
TA = 60°C
1.5
TJ = 125°C
1.0
D = Max
0.5
0.0
0
5
10 15 20 25 30 35
INPUT VOLTAGE (V)
Typical 5.0V Output SOA
Typical 1.8V Output SOA
Standard Configuration
Typical 3.3V Output SOA
5.0
TA = 25°C
TJ = 125°C
D = Max
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
TA = 60°C
TJ = 125°C
D = Max
0
5
10 15 20 25 30 35
INPUT VOLTAGE (V)
Typical 2.5V Output SOA
Typical 1.8V Output SOA
* IOUT <3A, D1: Diode Inc. B340 (3A/40V)
OUT <3A, D1: SBM1040 (10A/40V)
I
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MIC4685
Functional Characteristics
Frequency Foldback
The MIC4685 folds the switching frequency back during
a hard short circuit condition to reduce the energy per
cycle and protect the device.
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MIC4685
Functional Diagram
VIN
IN
Bootstrap
Charger
Enable
Internal
Regulator
R1
R2
⎛
⎜
⎝
⎞
⎟
VOUT = VREF
+1
⎠
⎛ VOUT
⎞
R1= R2
–1
⎟
200kHz
Oscillator
Thermal
Shutdown
Current
Limit
⎜
V
⎝
⎠
REF
VREF = 1.235V
Com-
parator
VOUT
COUT
SW
FB
Driver
Reset
R1
R2
Error
Amp
1.235V
Bandgap
Reference
MIC4685
Figure 1. Adjustable Regulator
A higher feedback voltage increases the error amplifier
output voltage. higher error amplifier voltage
Functional Description
The MIC4685 is a variable duty cycle switch-mode
regulator with an internal power switch. Refer to the
above block diagram.
A
(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 MIC4685 uses a voltage-
mode control architecture.
Supply Voltage
The MIC4685 operates from a +4V to +30V (34V
transient) unregulated input. Highest efficiency operation
is from a supply voltage around +12V. See the efficiency
curves in the “Typical Characteristics” section on page 5.
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.
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.
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
.
Feedback
Output Capacitor
In the adjustable version, an external resistive voltage
divider is required from the output voltage to ground,
center tapped to the FB pin. See Table 1 and Table 2 for
recommended resistor values.
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.
Duty Cycle Control
A fixed-gain error amplifier compares the feedback
signal with a 1.235V 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.
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MIC4685
The efficiency is used to determine how much of the
output power (POUT) is dissipated in the regulator circuit
(PD).
Application Information
Adjustable Regulators
Adjustable regulators require a 1.235V feedback signal.
Recommended voltage-divider resistor values for
common output voltages are detailed in Table 1.
POUT
PD
PD
=
=
− POUT
η
For other voltages, the resistor values can be
determined using the following formulas:
7.5W
0.84
− 7.5W
R1
R2
⎛
⎜
⎞
PD = 1.43W
A worst-case rule of thumb is to assume that 80% of the
VOUT = VREF
+ 1
⎟
⎝
⎠
total output power dissipation is in the MIC4685 (PD(IC)
and 20% is in the diode-inductor-capacitor circuit.
)
⎛
⎞
VOUT
VREF
⎜
⎟
− 1
R1 = R2
⎜
⎟
⎝
⎠
PD(IC) = 0.8 PD
PD(IC) = 0.8 × 1.43W
PD(IC) = 1.14W
V
REF = 1.235V
Thermal Considerations
Calculate the worst-case junction temperature:
TJ = PD(IC) θJC + (TC – TA) + TA(max)
where:
The MIC4685 is capable of high current due to the
thermally optimized SPAK package.
One limitation of the maximum output current on any
MIC4685 design is the junction-to-ambient thermal
resistance (θJA) of the design (package and ground
plane).
TJ = MIC4685 junction temperature
PD(IC) = MIC4685 power dissipation
θJC = junction-to-case thermal resistance.
Examining θJA in more detail:
The θJC for the MIC4685’s 7-pin SPAK is approximately
2.2°C/W.
θ
JA = (θJC + θCA)
TC = “pin” temperature measurement taken at
the Tab.
where:
θ
θ
JC = junction-to-case thermal resistance
CA = case-to-ambient thermal resistance
TA = ambient temperature
TA(max) = maximum ambient operating temp-
erature for the specific design.
θJC is a relatively constant 2.2°C/W for a 7-pin SPAK.
θCA is dependent upon layout and is primarily governed
by the connection of pins 4, and Tab to the ground
plane. The purpose of the ground plane is to function as
a heat sink.
Calculating the maximum junction temperature given a
maximum ambient temperature of 60°C:
TJ = 1.14 × 2.2°C + (46°C – 25°C) + 60°C
TJ = 83.5°C
Checking the Maximum Junction Temperature:
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.” Also refer to the
“Typical Safe Operating Area (SOA)” graphs in this
document.
For this example, with an output power (POUT) of 7.5W,
(5V output at 1.5A with VIN = 12V) and 60°C maximum
ambient temperature, what is the junction temperature?
Referring to the “Typical Characteristics: 5V Output
Efficiency” graph, read the efficiency (η) for 1.5A output
current at VIN = 12V or perform you own measurement.
η = 84%
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MIC4685
Layout Considerations
Bootstrap Diode
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.
The bootstrap diode provides an external bias source
directly to the main pass element, this reduces VSAT thus
allowing the MIC4685 to be used in very low head-room
applications i.e., 5VIN to 3.3VOUT with high efficiencies.
Bootstrap diode not for use if VIN exceeds 16V, VIN. See
Figure 2.
To minimize stray inductance and ground loops, keep
trace lengths as short as possible. For example, keep
D1 close to pin 6 and pin 4, and Tab, keep L1 away from
sensitive node FB, and keep CIN close to pin 2 and pin 4,
and Tab. 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 6.
Gerber files are available upon request.
VIN
+4V to +30V
MIC4685_R
(34V transient)
2
5
1
6
IN
EN
BS
L1
VOUT
R1
SW
CIN
39µH
COUT
3
FB
7-pin
SPAK
GND
D1
4,Tab
R2
4, Tab
GND
Figure 2. Critical Traces for Layout
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MIC4685
Recommended Components for a Given Output Voltage (Bootstrap Configuration)
VOUT
IOUT
*
R1
R2
VIN
C1
D1
D2
L1
C4
5.0V
2.1A
3.01k
976Ω
7.5V – 16V
47µF, 20V
Vishay-Dale
595D476X0020D2T + Vishay
B330A
3A, 30V
Schottky
1A, 20V
Schottky
B120-E3
39µH
Sumida
CDRH127R-390MC
330µF, 6.3V
Vishay-Dale
594D337X06R3D2T
3.3V
2.5V
1.8V
2.2A
2.0A
2.0A
3.01k
3.01k
3.01k
1.78k
2.94k
6.49k
6.0V – 16V
5.0V – 16V
5.0V – 16V
47µF, 20V
Vishay-Dale
595D476X0020D2T B330A
3A, 30V
Schottky
1A, 20V
Schottky
B120-E3
39µH
Sumida
CDRH127R-390MC
330µF, 6.3V
Vishay-Dale
594D337X06R3D2T
47µF, 20V
Vishay-Dale
595D476X0020D2T B330A
3A, 30V
Schottky
1A, 20V
Schottky
B120-E3
39µH
Sumida
CDRH127R-390MC
330µF, 6.3V
Vishay-Dale
594D337X06R3D2T
47µF, 20V
Vishay-Dale
595D476X0020D2T + Vishay
B330A
3A, 30V
Schottky
1A, 20V
Schottky
B120-E3
39µH
Sumida
CDRH127R-390MC
330µF, 6.3V
Vishay-Dale
594D337X06R3D2T
*
Maximum output current at minimum input voltage. See SOA curves for maximum output current vs. Input voltage.
Table 1. Recommended Components for Common Output Voltages
D2
MBRX120
1A/20V
JP3
L1
39µH
J1
J2
U1 MIC4685_R
VIN
VOUT
2
5
6
IN
SW
C3
0.33µF
50V
1
3
C2
0.1µF
50V
BS
FB
C4*
optional
R1
R2
C1
ON
47µF
20V
J3
GND
EN
C5
330µF
6.3V
C7
0.1µF
50V
OFF
D1
GND
4, Tab
B330A
or
SS33
J4
GND
* C4 can be used to provide additional stability
and improved transient response.
Note: optimized for 5VOUT
Figure 3. Schematic Diagram
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MIC4685
Recommended Components for a Given Output Voltage (Standard Configuration)
VOUT
IOUT
*
R1
R2
VIN
C1
D1
L1
C5
5.0V
2.0A
3.01k
976Ω
8V – 30V
33µF, 35V
Vishay-Dale
3A, 40V
Schottky
39µH
Sumida
330µF, 6.3V
Vishay-Dale
595D336X0035R2T B340A-E3 CDRH127-390MC
594D337X06R3D2T
3.3V
2.5V
1.8V
2.4A
3.01k
3.01k
3.01k
1.78k
2.94k
6.49k
8V – 26V
7V – 23V
6V – 16V
33µF, 35V
Vishay-Dale
3A, 40V
Schottky
39µH
Sumida
330µF, 6.3V
Vishay-Dale
594D337X06R3D2T
595D336X0035R2T B340A-E3 CDRH127-390MC
2.35A
2.0A
33µF, 35V
Vishay-Dale
3A, 40V
Schottky
39µH
Sumida
330µF, 6.3V
Vishay-Dale
594D337X06R3D2T
595D336X0035R2T B340A-E3 CDRH127-390MC
33µF, 35V
Vishay-Dale
3A, 40V
Schottky
39µH
Sumida
330µF, 6.3V
Vishay-Dale
595D336X0035R2T + Vishay
B340A-E3
CDRH127-390MC
594D337X06R3D2T
*
Maximum output current at minimum input voltage. See SOA curves for maximum output current vs. Input voltage.
Table 2. Recommended Components for Common Output Voltages
D2***
B340
JP3
J1
VIN
J2
VOUT
2A
L1
39µH
U1 MIC4685_R
(34V transient)
2
5
6
IN
SW
C3
0.33µF
50V
1
3
C2
0.1µF
50V
BS
FB
C4*
R1
optional
C1
33µF
35V
J3
GND
3.01k
ON
EN
C5
330µF
6.3V
C7
0.1µF
50V
OFF
D1
B340A
R2
6.49k
R3
2.94k
R4
1.78k
R5
C6**
GND
4, Tab
976W
1
2
3
5
7
JP1a
1.8V
JP1b
2.5V
JP1c
3.3V
JP1d
5.0V
J4
GND
8
4
6
* C4 can be used to provide additional stability
and improved transient response.
Note: optimized for 5VOUT
** C6 Optional
*** D2 is not used for standard configuration and JP3 is open.
Figure 4. Evaluation Board Schematic Diagram
M9999-012610
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Micrel, Inc.
MIC4685
Printed Circuit Board
Figure 5a. Top Layer
Figure 5b. Bottom Layer
M9999-012610
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Micrel, Inc.
MIC4685
Abbreviated Bill of Materials (Critical Components)
Item
C1
Part Number
594D336X0035R2T
VJ0805Y104KXAAB
GRM426X7R334K50
VJ1206Y334KXAAT
Optional
Manufacturer
Vishay Sprague(1)
Vitramon
Description
33µF 35V
Qty.
1
2
C2, C7
0.1µF 50V
Murata(5)
Vishay(1)
0.33µF, 50V ceramic capacitor
0.33µF, 50V ceramic capacitor
1800pF, 50V ceramic
330µF, 6.3V, tantalum
Schottky 3A 40V
C3
C4*
C5
1
1
1
1
1
1
1
594D337X06R3D2T
B340A
Vishay Sprague(1)
Diode Inc(2)
Vishay(1)
B340LA-EA
Schottky 3A 40V
D1
SSA34A
Vishay(1)
Vishay(1)
Vishay(1)
Schottky 3A 40V
B340A
Schottky 3A 40V
B120-EA
Schottky 3A 40V
D2
B340A
Diode Inc(2)
Micro Commercial Component(4)
Sumida(3)
Schottky 3A 40V
1
MBRX120
Schottky 1A 20V
L1
R1
R2
R3
R4
R5
U1
CDRH127-390MC
CRCW08053011FKEY3
CRCW08056491FKEY3
CRCW08052941FKEY3
CRCW08051781FKEY3
CRCW08051781FKEY3
MIC4685BR/WR
39µH
1
1
1
1
1
1
1
Vishay(1)
Vishay(1)
Vishay(1)
Vishay(1)
Vishay(1)
Micrel, Inc.(6)
3K01, 1%, 1/10W, 805
6K49, 1%, 1/10W, 805
2K94, 1%, 1/10W, 805
1K78, 1%, 1/10W, 805
976Ω, 1%, 1/10W, 805
3A 200kHz SPAK Buck Regulator
Notes:
1. Vishay Sprague, Inc.: www.vishay.com
2. Diodes Inc.: www.diodes.com
3. Sumida: www.sumida.com
4. Micro Commercial Component: www.mccsemi.com
5. Murata: www.murata.com
6. Micrel, Inc.: www.website.com
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Micrel, Inc.
MIC4685
Package Information
7-SPAK (R)
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB 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 a Purchaser’s own risk and Purchaser agrees to fully
indemnify Micrel for any damages resulting from such use or sale.
© 2004 Micrel, Incorporated.
M9999-012610
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