MIC28510 Evaluation Board
75V/4A Hyper Speed Control™
Synchronous DC/DC Buck Regulator
General Description
The MIC28510 DC/DC regulator operates over an
input supply range of 4.5V to 75V and provides a
regulated output at up to 4A of output current. The
output voltage is adjustable down to 0.8V with a
typical accuracy of ±1%. The switching frequency is
adjustable and once adjusted the switching frequency
remains fairly constant with changes in input voltage
and output load.
The basic parameters of the evaluation board are:
•
•
•
Input Voltage
−
5V to 75V
Output Voltage
−
0.8V to 5V at 4A
(1)
(2)
12V at up to 4A
250kHz Switching Frequency
(Adjustable from 100kHz to 500kHz)
Getting Started
1.
V
IN
Supply.
Connect a power supply to the VIN
and GND terminals, paying careful attention to the
polarity and supply voltage range (5V
<
VIN
<
75V). The input current IIN can be monitored with
a current meter. Do not apply power until Step 4.
2.
Connect Load and Monitor Output.
Connect a
load to the V
OUT
and GND terminals. The load can
be either a passive (resistive) or an active (as in
an electronic load) type. A current meter may be
placed between the V
OUT
terminal and load to
monitor the output current. Ensure the output
voltage is monitored at the V
OUT
terminal.
3.
Enable Input.
The EN pin has an internal 100k
pull-up resistor to VDD, which allows the output to
be turned on when VDD exceeds its UVLO
threshold. An EN connector is provided on the
evaluation board for users to easily access the
enable feature. Applying an external logic signal
on the EN pin to pull it low or using a jumper to
short the EN pin to GND will shut off the output of
the MIC28510 evaluation board.
4.
Turn On the Power.
Turn on the VIN supply and
verify that the output voltage is regulated to 3.3V.
Notes:
1, 2. Refer to thermal de-rating curves shown in Typical
Characteristics section.
Datasheets and support documentation can be found
on Micrel’s web site at:
www.micrel.com
Requirements
The MIC28510 evaluation board requires only a single
power supply with at least 10A current capability. A
linear regulator, which includes a Zener and an NPN
transistor, has been installed on the board to provide
housekeeping (V
DD
) for the MIC28510. The output
load can either be a passive or an active load.
Precautions
The MIC28510 evaluation board does not have
reverse polarity protection. Applying a negative
voltage to the PVIN and GND terminals may damage
the device. The maximum PVIN of the board is rated
at 75V. Exceeding 75V on the PVIN could damage the
device.
Ordering Information
Part Number
MIC28510 5V EV
MIC28510 12V EV
Description
Evaluation Board up to 5V Output
Evaluation Board 12V Output
Hyper Speed Control 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
March 2012
M9999-030712
hbwhelp@micrel.com
or (408) 955-1690
Micrel, Inc.
MIC28510 4A Evaluation Board
The switching frequency can be adjusted between
100kHz and 500kHz by changing the resistor divider
connected network consisting of R18 and R19 from
PVIN to PGND.
Features
Feedback Resistors
The output voltage on the MIC28510 evaluation
board, which is preset to 3.3V, is determined by the
feedback divider, shown in Equation 1:
⎛
R4
V
OUT
=
V
REF
× ⎜
1
+
⎜
R
BOTTOM
⎝
⎞
⎟
⎟
⎠
Eq. 1
where V
REF
= 0.8V, and R
BOTTOM
is one of R5-R12,
which corresponds to 0.9V, 1.0V, 1.2V, 1.5V, 1.8V,
2.5V, 3.3V, or 5V. Leaving the R
BOTTOM
open gives a
0.8V output voltage. All other voltages not listed
above can be set by modifying R
BOTTOM
value
according to Equation 2:
R
BOTTOM
=
R4
×
V
REF
V
OUT
−
V
REF
Eq. 2
Figure 1. Switching Frequency Adjustment
Note that the output voltage should not be set to
exceed 5V due to the 6.3V voltage rating on the
output capacitors.
If higher than 5V output is desired, it is recommended
to use the designs shown in the MIC28510 12V/4A
output evaluation board schematic, where the output
capacitors, L1, R3, and R17 are optimized for 12V
output.
SW Node
Test point J11 (V
SW
) is placed for monitoring the
switching waveform, one of the most critical
waveforms for the converter.
Current Limit
The MIC28510 has internal FETs, and the current limit
is implemented by sensing the R
DS-ON
of bottom FET.
The MIC28510 has a fixed current limit of 6.5A
(typical).
Loop Gain Measurement
The resistor, R13, is placed in series with the regulator
feedback path. The control loop gain can be
measured by connecting an impedance analyzer
across the resistor and selecting the resistor value in
between 20Ω to 50Ω.
Setting the Switching Frequency
The
MIC28510
is
an
adjustable-frequency,
synchronous buck regulator featuring a unique
digitally
modified
adaptive
on-time
control
architecture.
Equation 3 illustrates the estimated switching frequency:
f
SW_ADJ
=
f
O
×
R19
R18
+
R19
Eq. 3
where f
O
= Switching Frequency when R18 is 100k
and R19 being open, f
O
should be typically 450kHz.
For more precise setting, it is recommended to use
Figure 2:
Figure 2. Switching Frequency vs. R19
The evaluation board design is optimized for a
switching frequency of 250kHz. If the switching
frequency is programmed to either lower end or higher
end, the design needs optimization.
2
M9999-030712
hbwhelp@micrel.com
or (408) 955-1690
March 2012
Micrel, Inc.
MIC28510 4A Evaluation Board
MIC28510 0.8V to 5V/4A Evaluation Board Typical Characteristics
Efficiency (V
IN
= 48V)
vs. Output Current
100
90
Thermal Derating
4
V
OUT
= 3.3V
fsw = 250kHz
L = 10µH
T
j_MAX
=125°C
4
Thermal Derating
V
IN
= 8V
LOAD CURRENT (A)
LOAD CURRENT (A)
80
EFFICIENCY (%)
70
60
50
40
30
20
f
SW
= 250kHz
5.0V
3.3V
2.5V
1.8V
1.5V
1.2V
1.0V
0.9V
0.8V
3
3
V
IN
= 48V
2
V
IN
= 75V
1
V
IN
= 48V
V
IN
= 5V
0
2
V
IN
= 75V
V
OUT
= 5V
f
SW
= 250kHz
L = 10µH
T
j_MAX
= 125°C
25
40
55
70
85
100
1
0
25
40
55
70
85
100
10
0
1
2
3
4
5
6
OUTPUT CURRENT (A)
MAXIMUM AMBIENT TEMPERATURE
(°C)
MAXIMUM AMBIENT TEMPERATURE
(°C)
Thermal Derating
4
V
OUT
= 5V
f
SW
= 250kHz
L = 10µH
T
j_MAX
= 125°C
Thermal Derating
4
V
OUT
= 3.3V
f
SW
= 250kHz
L = 10µH
T
j_MAX
= 125°C
4
Thermal Derating
V
OUT
= 2.5V
LOAD CURRENT (A)
LOAD CURRENT (A)
3
3
LOAD CURRENT (A)
V
IN
=18V
V
IN
= 12V
3
f
SW
= 250kHz
L = 10µH
T
j_MAX
= 125°C
V
IN
= 12V
V
IN
=18V
2
2
V
IN
=18V
2
V
IN
= 24V
1
1
V
IN
= 24V
1
V
IN
= 24V
V
IN
= 12V
0
25
40
55
70
85
100
0
25
40
55
70
85
100
0
25
40
55
70
85
100
MAXIMUM AMBIENT TEMPERATURE
(°C)
MAXIMUM AMBIENT TEMPERATURE
(°C)
MAXIMUM AMBIENT TEMPERATURE
(°C)
Die Temperature* :
The temperature measurement was taken at the hottest point on the MIC28510 case mounted on a 5 square inch 4 layer, 0.62”,
FR-4 PCB with 2oz. finish copper weight per layer, see Thermal Measurement section. Actual results will depend upon the size of the PCB, ambient
temperature and proximity to other heat emitting components.
March 2012
3
M9999-030712
hbwhelp@micrel.com
or (408) 955-1690
Micrel, Inc.
MIC28510 4A Evaluation Board
MIC28510 0.8V to 5V/4A Output Evaluation Board Schematic
MIC28510 Evaluation Board for 0.8V to 5V/4A Output
March 2012
4
M9999-030712
hbwhelp@micrel.com
or (408) 955-1690
Micrel, Inc.
MIC28510 4A Evaluation Board
Bill of Materials 0.8V to 5V/4A Output
Item
C1
C2, C3
C13
Part Number
EEU-FC2A101B
GRM32ER72A225KA35L
C3225X7R2A225KT5
GRM32ER60J107ME20L
12106D107MAT2A
06035C104KAT2A
GRM188R71H104KA93D
C1608X7R1H104K
GRM188R72A104KA35D
C1608X7S2A104K
0805ZC225MAT2A
GRM21BR71A225KA01L
C2012X7R1A225K
GRM188R72A102KA01D
C1608X7R2A102K
06031C102KAT2A
GRM188R71H472KA01D
C1608X7R2A472K
06035C472KAT2A
GRM21BR71A105KA01L
C2012X7R1A105K
Open
BAT46W-TP
BAT46W-7-F
MMXZ5232B-TP
CMDZ5L6
DR125-100-R
FCX493
CRCW06034R75FKEA
CRCW08051R21FKEA
CRCW060316K5FKEA
CRCW060310K0FKEA
CRCW060380K6FKEA
CRCW060340K2FKEA
MCC
(5)
Diodes Inc.
(6)
MCC
(5)
Central Semi
(7)
Cooper Bussmann
(8)
Diodes Inc/ZETEX
(6)
Vishay Dale
(9)
Vishay Dale
(9)
Vishay Dale
(9)
Vishay Dale
(9)
Vishay Dale
(9)
Vishay Dale
(9)
Small Signal Schottky Diode
5.6V Zener Diode
10µH Inductor, 5.35A RMS, 7A Saturation Current
100V NPN Transistor
4.75Ω Resistor, Size 0603, 1%
1.21Ω Resistor, Size 0805, 1%
16.5kΩ Resistor, Size 0603, 1%
10kΩ Resistor, Size 0603, 1%
80.6kΩ Resistor, Size 0603, 1%
40.2kΩ Resistor, Size 0603, 1%
1
1
1
1
1
2
1
1
1
1
Manufacturer
Panasonic
(1)
Murata
(2)
(3)
TDK
Murata
(2)
(4)
AVX
AVX
(4)
Murata
(2)
(3)
TDK
Murata
(2)
(3)
TDK
AVX
(4)
Murata
(2)
TDK
(3)
Murata
(2)
TDK
(3)
(4)
AVX
Murata
(2)
TDK
(3)
(4)
AVX
Murata
(2)
(3)
TDK
Description
100µF Aluminum Capacitor, SMD, 100V
2.2µF Ceramic Capacitor, X7R, Size 1210, 100V
100µF Ceramic Capacitor, X5R, Size 1210, 6.3V
Qty.
1
2
1
C6
0.1µF Ceramic Capacitor, X7R, Size 0603, 50V
1
C10
0.1µF Ceramic Capacitor, X7R, Size 0603, 100V
1
C8, C9
2.2µF Ceramic Capacitor, X7R, Size 0805, 10V
2
C11
1nF Ceramic Capacitor, X7R, Size 0603, 100V
1
C12
4.7nF Ceramic Capacitor, X7R, Size 0603, 50V
1
C16
C4, C5, C7,
C14, C15
D1
D2
L1
Q1
R1
R2, R16
R3
R4
R5
R6
1µF Ceramic Capacitor, X7R, Size 0805, 10V
1
March 2012
5
M9999-030712
hbwhelp@micrel.com
or (408) 955-1690
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