Micrel MIC24056 User manual

MIC24056 Evaluation Board
12A, High-Efficiency, Synchronous DC/DC
Buck Regulator with HyperLight Load
®
SuperSwitcher II™
HyperLight Load is a registered trademark of Micrel, Inc.
Hyper Speed Control, SuperSwitcher II, and Any Capacitor are trademarks of Micrel, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel [phone] • fax + 1 [phone] • http://www.micrel.com
February 11, 2013
Revision 1.0
General Description
The MIC24056 DC/DC synchronous buck regulator operates
over an input supply range of 4.5V to 19V and provides a
regulated output at up to 12A of load current. The output
voltage is adjustable down to 0.8V with a typical accuracy of
±1%.
Micrel’s HyperLight Load®architecture maintains high
efficiency under light load conditions by transitioning to
variable frequency, discontinuous mode operation. The
Hyper Speed Controlallows using smaller output
capacitance. The device operates at a switching frequency of
600kHz, which remains relatively constant with changes in
input voltage and output load.
The MIC24056 utilizes an adaptive TON ripple control
architecture. An undervoltage lockout feature is provided to
ensure proper operation under power-sag conditions. An
internal soft-start feature is provided to reduce the inrush
current. Foldback current limit and “hiccup” mode short-circuit
protection and thermal shutdown ensures protection of the IC
during fault conditions.
The HyperLight Load and Hyper Speed Control features
allow ideal transition from light load to full load and vice versa.
The 19V operating rating of the device provides ample design
safety margin for 12V input applications.
The basic parameters of the MIC24056 evaluation board are
a VIN supply of 5V to 19V, output voltage of 0.8V to 5V at
12A(1), and 600kHz switching frequency.
Note:
1. Refer to the temperature curves presented in the Evaluation Board
Performance section. Also, note that the typical minimum input
voltage to maximum output voltage conversion is limited by the
maximum duty cycle.
Datasheets and support documentation are available on
Micrel’s web site at: www.micrel.com.
Requirements
The MIC24056 evaluation board requires only a single
power supply with at least 10A current capability. The
MIC24056 has internal VDD LDO so no external linear
regulator is required to power the internal biasing of the IC.
When VIN < 5.5V, VDD should be tied to PVIN pins to
bypass the internal linear regulator by a jumper. The
output load can either be an active or passive load.
Power-Up Precautions
The evaluation board does not have reverse polarity
protection. Applying a negative voltage to the VIN terminal
may damage the device. The maximum VIN operating
voltage of the MIC24056 evaluation board is 19V. It has
two different layout designs, one (Figure 1) optimized for
evaluation and a second (Figure 2) optimized for a smaller
footprint. The evaluation board is only populated with
components shown in Figure 1.
Getting Started
1. VIN Supply.
Connect a supply to the VIN and GND terminals,
paying careful attention to the polarity and the supply
range (5V < VIN < 19V). An ammeter may be placed
between the input supply and the VIN terminal to the
evaluation board. Ensure that the supply voltage is
monitored at the VIN terminal. The ammeter and/or
power lead resistance can reduce the voltage supplied
to the input. Do not apply power until Step 4.
2. Connect the load to the VOUT and ground
terminals.
The load can be either passive (resistive) or active (as
in an electronic load). An ammeter can be placed
between the load and the VOUT terminal. Ensure that
the output voltage is monitored at the VOUT terminal.
3. Enable Input.
An EN connector is provided on the evaluation board
for users to easily access the enable feature. The
output of the MIC24056 turns on when VDDexceeds
the UVLO threshold. The output of the MIC24056 may
be turned off by shorting the EN pin to ground.
4. Turn on the power.
Turn on VIN power supply and verify that the output
voltage is regulated to 1.8V.
Ordering Information
Part Number Description
MIC24056YJL EV 12A HLL DC/DC Buck Regulator
Evaluation Board

Micrel, Inc.
MIC24056 Evaluation Board
February 11, 2013
2 Revision 1.0
Output Voltage
The output voltage on the MIC24056 evaluation board is
adjustable. It is set by adjusting the feedback resistors,
referring Equation 1:







+×=
BOTTOM
FBOUT RR4
1VV
Eq. 1
where VFB = 0.8V and RBOTTOM is one of the R5, R6, R7,
R8, R9, R10, R11, R12 which corresponds to 0.9V, 1.0V,
1.2V, 1.5V, 1.8V, 2.5V, 3.3V, or 5V. Leaving the RBOTTOM
open gives a 0.8V output voltage. The output voltage
above is set at the factory for a 1.8V output, but it can
easily be changed by moving the jumper to a respective
position to get an indicated voltage on the board. If a
desired voltage is not shown on the board, it is easily
modified by removing RBOTTOM and replacing it with the
values that yield the desired output voltage. Once R4 is
selected, RBOTTOM can be calculated using Equation 2:
FBOUT
FB
BOTTOM VV
VR4
R−
×
=
Eq. 2
For VFB = 0.8V, as in Equation 3:
0.8VV 0.8VR4
ROUT
BOTTOM −
×
=
Eq. 3
The output voltage should not be set to exceed 5V due to
the 6.3V rating of the output capacitor and limitation on line
regulation. Please refer to the “Setting the Output Voltage”
and Ripple Injection” subsections in the Application
Information section of the MIC24056 datasheet for more
detailed information.

Micrel, Inc.
MIC24056 Evaluation Board
February 11, 2013
3 Revision 1.0
Evaluation Board Performance
Die Temperature* : The temperature measurement was taken at the hottest point on the MIC24056 case mounted on a 5 square inch 4 layer, 0.62 inch,
FR-4 PCB with 2oz finish copper weight per layer, see the Thermal Measurement section in the MIC24056 datasheet. Actual results will depend upon
the size of the PCB, ambient temperature and proximity to other heat-emitting components.
50
55
60
65
70
75
80
85
90
95
100
0 3 6 9 12 15
EFFICIENCY (%)
OUTPUT CURRENT (A)
Efficiency (VIN = 5V)
vs. Output Current
3.3V
2.5V
1.8V
1.5V
1.2V
1.0V
0.9V
0.8V
VIN = 5V
50
55
60
65
70
75
80
85
90
95
100
0 3 6 9 12 15
EFFICIENCY (%)
OUTPUT CURRENT (A)
Efficiency (VIN = 12V)
vs. Output Current
5.0V
3.3V
2.5V
1.8V
1.5V
1.2V
1.0V
0.9V
0.8V
VIN = 12V
0
20
40
60
80
100
0246810 12
DIE TEMPERATURE (°C)
OUTPUT CURRENT (A)
Die Temperature* (VIN = 5V)
vs. Output Current
VIN = 5V
V
OUT
= 1.8V
0
20
40
60
80
100
0 2 4 6 8 10 12
DIE TEMPERATURE (°C)
OUTPUT CURRENT (A)
Die Temperature* (VIN = 12V)
vs. Output Current
VIN = 12V
V
OUT
= 1.8V

Micrel, Inc.
MIC24056 Evaluation Board
February 11, 2013
4 Revision 1.0
Evaluation Board Schematic
Figure 1. Schematic of MIC24056 Evaluation Board
(J11, R13, and R15 are for testing purposes)

Micrel, Inc.
MIC24056 Evaluation Board
February 11, 2013
5 Revision 1.0
Evaluation Board Schematic (Continued)
Figure 2. Schematic of MIC24056 Evaluation Board
−
Optimized for Smaller Footprint
(J11, R13, and R15 are for testing purposes)

Micrel, Inc.
MIC24056 Evaluation Board
February 11, 2013
6 Revision 1.0
Bill of Materials
Item Part Number Manufacturer Description Qty.
C1 Open
C2, C3
12103C475KAT2A
AVX(1)
4.7µF Ceramic Capacitor, X7R, Size 1210, 25V 2
GRM32DR71E475KA61K
Murata(2)
C3225X7R1E475K
TDK(3)
C4, C5, C13
12106D107MAT2A
AVX
100µF Ceramic Capacitor, X5R, Size 1210, 6.3V 3
GRM32ER60J107ME20L
Murata
C3225X5R0J107M
TDK
C15
Open
C6, C7, C10
06035C104KAT2A
AVX
0.1µF Ceramic Capacitor, X7R, Size 0603, 50V 3
GRM188R71H104KA93D
Murata
C1608X7R1H104K
TDK
C8
0603ZC105KAT2A
AVX
1.0µF Ceramic Capacitor, X7R, Size 0603, 10V 1
GRM188R71A105KA61D
Murata
C1608X7R1A105K
TDK
C9
0603ZD225KAT2A
AVX
2.2µF Ceramic Capacitor, X5R, Size 0603, 10V 1
GRM188R61A225KE34D
Murata
C1608X5R1A225K
TDK
C12
06035C472KAZ2A
AVX
4.7nF Ceramic Capacitor, X7R, Size 0603, 50V 1
GRM188R71H472K
Murata
C1608X7R1H472K
TDK
C14
B41851F7227M
EPCOS(4)
220µF Aluminum Capacitor, 35V
1
C11, C16
Open
D1
SD103AWS
MCC(5)
40V, 350mA, Schottky Diode, SOD323 1
SD103AWS-7
Diodes Inc.(6)
SD103AWS
Vishay(7)
L1
HCF1305-2R2-R
Cooper Bussmann(8)
2.2µH Inductor, 15A Saturation Current
1
R1
CRCW06032R21FKEA
Vishay Dale
2.21Ω Resistor, Size 0603, 1%
1
R2
CRCW06032R00FKEA
Vishay Dale
2.00Ω Resistor, Size 0603, 1%
1
R3
CRCW060319K6FKEA
Vishay Dale
19.6kΩResistor, Size 0603, 1%
1
R4
CRCW06032K49FKEA
Vishay Dale
2.49kΩResistor, Size 0603, 1%
1
R5
CRCW060320K0FKEA
Vishay Dale
20.0kΩResistor, Size 0603, 1%
1
Notes:
1. AVX:www.avx.com.
2. Murata: www.murata.com.
3. TDK: www.tdk.com.
4. EPCOS: www.epcos.com.
5. MCC: www.mccsemi.com.
6. Diodes, Inc.: www.diodes.com.
7. Vishay: www.vishay.
8. Cooper Bussmann: www.cooperbussmann.com.

Micrel, Inc.
MIC24056 Evaluation Board
February 11, 2013
7 Revision 1.0
Bill of Materials (Continued)
Item Part Number Manufacturer Description Qty.
R6, R14, R17
CRCW060310K0FKEA
Vishay Dale
10.0kΩResistor, Size 0603, 1%
3
R7
CRCW06034K99FKEA
Vishay Dale
4.99kΩResistor, Size 0603, 1%
1
R8
CRCW06032K87FKEA
Vishay Dale
2.87kΩResistor, Size 0603, 1%
1
R9
CRCW06032K006FKEA
Vishay Dale
2.00kΩResistor, Size 0603, 1%
1
R10
CRCW06031K18FKEA
Vishay Dale
1.18kΩResistor, Size 0603, 1%
1
R11
CRCW0603806RFKEA
Vishay Dale
806Ω Resistor, Size 0603, 1%
1
R12
CRCW0603475RFKEA
Vishay Dale
475Ω Resistor, Size 0603, 1%
1
R13
CRCW06030000FKEA
Vishay Dale
0ΩResistor, Size 0603, 5%
1
R15
CRCW060349R9FKEA
Vishay Dale
49.9ΩResistor, Size 0603, 1%
1
R16, R18
CRCW06031R21FKEA
Vishay Dale
1.21Ω Resistor, Size 0603, 1%
2
R20
Open
All Reference
designators ending
with “A”
Open
U1 MIC24056YJL Micrel. Inc.(9)
12A, High-Efficiency, Synchronous DC/DC
Buck Regulator with Hyper Light Load
1
Note:
9. Micrel, Inc.: www.micrel.com.

Micrel, Inc.
MIC24056 Evaluation Board
February 11, 2013
8 Revision 1.0
PCB Layout Recommendations(1)
Top Layer
Mid-Layer 1
Note:
1. Refer to “PCB Layout Guideline” section for component placement and layout in MIC24056 datasheet on Micrel web page (www.micrel.com)

Micrel, Inc.
MIC24056 Evaluation Board
February 11, 2013
9 Revision 1.0
PCB Layout Recommendations(1)(Continued)
Mid-Layer 2
Bottom Layer

Micrel, Inc.
MIC24056 Evaluation Board
February 11, 2013
10 Revision 1.0
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TEL [phone] FAX [phone] WEB http://www.micrel.com
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A
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