MIC2103/04 Evaluation Board
75V, Synchronous Buck Controllers
featuring Adaptive On-Time Control
Hyper Speed Control™ Family
General Description
The Micrel MIC2103/04 are constant-frequency,
synchronous buck controllers featuring a unique
adaptive
on-time
control
architecture.
The
MIC2103/04 operates over an input supply range of
4.5V to 75V and can be used to supply up to 15A of
output current. The output voltage is adjustable down
to 0.8V with a guaranteed accuracy of ±1%. The
device operates with programmable switching
frequency from 200kHz to 600kHz.
The MIC2103 has Hyper Light Load
®
architecture, so it
can operate in pulse skipping mode at light load.
However, from medium load to heavy load, it operates in
fixed frequency CCM mode. The MIC2104 has Hyper
Speed Control architecture which operates in fixed
frequency CCM mode under all load conditions.
The basic parameters of the evaluation board are:
1. Input: 12V to 75V
2. Output: 0.8V to 5V at 10A
(1)
3. 200kHz Switching Frequency (Adjustable 200kHz
to 600kHz)
Note:
1. Refer to temperature curves shown in Typical Characteristics
section.
the device. The maximum VIN of the board is rated at
75V. Exceeding 75V on the VIN could damage the
device.
Getting Started
1.
VIN Supply
Connect a supply to the VIN and GND terminals,
paying careful attention to the polarity and the supply
range (12V < VIN < 75V). Monitor I
IN
with a current
meter and input voltage at VIN and GND terminals
with voltmeter. Do not apply power until step 4.
2.
Connect Load and Monitor Output
Connect a load to the VOUT 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 VOUT terminal and load to
monitor the output current. Ensure the output voltage
is monitored at the VOUT terminal.
3.
Enable Input
The EN pin has an on board 100k pull-up resistor
(R22) to VIN, 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 MIC2103/04 evaluation board.
4.
Turn on the Power
Turn on the VIN supply and verify that the output
voltage is regulated to 5.0V.
Datasheets and support documentation can be found
on Micrel’s web site at:
www.micrel.com.
Requirements
The MIC2103 and MIC2104 evaluation board requires
only a single power supply with at least 10A current
capability. The MIC2103/04 has internal VDD LDO so
no external linear regulator is required to power the
internal biasing of the IC. In the applications with
VIN < +5.5V, VDD should be tied to VIN to by-pass
the internal linear regulator. The output load can either
be a passive or an active load.
Precautions
The MIC2103/04 evaluation board does not have
reverse polarity protection. Applying a negative
voltage to the VIN and GND terminals may damage
Hyper Speed Control is a trademark of Micrel, Inc
Ordering Information
Part Number
MIC2103YML 10A EV
MIC2104YML 10A EV
Description
MIC2103 Evaluation Board up
to 5V Output
MIC2104 Evaluation Board up
to 5V Output
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 •
http://www.micrel.com
October 2012
M9999-100512
Micrel, Inc.
MIC2103/04 10A Evaluation Board
through the value of the resistor (R17). If the absolute
value of the voltage drop on the bottom FET is greater
than V
CL
, the V(ILIM) is lower than PGND and a short
circuit event is triggered. A hiccup cycle to treat the
short event is generated. The hiccup sequence,
including the soft start, reduces the stress on the
switching FETs and protects the load and supply for
severe short conditions.
Features
Feedback Resistors
The output voltage on the MIC2103/04 evaluation
board, which is preset to 5.0V, is determined by the
feedback divider:
V
OUT
½
V
REF
1
R
BOTTOM
R1
(Eq. 1)
where V
REF
= 0.8V, and R
BOTTOM
is one of R4, R5, R6,
R7, R8, R9, R10, R11 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:
R
BOTTOM
½
R1
V
REF
V
OUT
V
REF
(Eq. 2)
Figure 1. MIC2103/04 Current Limiting Circuit
Note that the output voltage should not be set to
exceed 5V due to the 6.3V voltage rating on the
output capacitors.
SW Node
Test point J1 (VSW) is placed for monitoring the
switching waveform, which is one of the most critical
waveforms for the converter.
The short circuit current limit can be programmed by
using the following formula.
(Eq. 3)
I
CL
Where I
CLIM
= Desired Current limit
Δ
PP
= Inductor current peak to peak
R
DS (ON)
= On resistance of low-side power MOSFET
V
CL
= Current limit threshold, the typical value is 14mV
in EC table
I
CL
= Current Limit source current, the typical value is
80µA in EC table.
In case of a hard short, the short limit is folded down
to allow an indefinite hard short on the output without
any destructive effect. It is mandatory to make sure
that the inductor current used to charge the output
capacitance during soft start is under the folded short
limit. Otherwise, the supply will go in hiccup mode and
may not be finishing the soft start successfully.
The MOSFET R
DS(ON)
varies 30% to 40% with
temperature; therefore, it is recommended to add a
50% margin to I
CL
in the above equation to avoid false
current limiting due to increased MOSFET junction
temperature rise. It is also recommended to connect
SW pin directly to the drain of the low-side MOSFET
to accurately sense the MOSFETs R
DS(ON)
.
R17
½
(
I
CLIM
PP
0.5)
R
DS
(
ON
)
V
CL
Current Limit
The MIC2103/04 uses the R
DS(ON)
and external
resistor connected from ILIM pin to SW node to
decide the current limit.
In each switching cycle of the MIC2103/04 converter,
the inductor current is sensed by monitoring the low-
side MOSFET in the OFF period. The sensed voltage
V(ILIM) is compared with the power ground (PGND)
after a blanking time of 150ns. In this way the drop
voltage over the resistor R17 (V
CL
) is compared with
the drop over the bottom FET generating the short
current limit. The small capacitor (C18) connected
from ILIM pin to PGND filters the switching node
ringing during the off time to allow a better short limit
measurement. The time constant created by R17 and
C18 should be much less than the minimum off time.
The V
CL
drop allows programming of short limit
October 2012
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M9999-100512
Micrel, Inc.
Loop Gain Measurement
The resistor, R14, 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 20
Ω
to 50
Ω
.
Setting the Switching Frequency
The
MIC2103/04
are
adjustable-frequency,
synchronous buck controllers featuring a unique
adaptive on-time control architecture. The switching
frequency can be adjusted between 200kHz and
600kHz by changing the resistor divider network
consisting of R19 and R20.
MIC2103/04 10A Evaluation Board
Switching Frequency
700
R19 = 100k, I
OUT
=10A
600
500
VIN = 48V
VIN = 12V
SW FREQ (kHz)
400
300
200
100
0
10.00
VIN =75V
V
DD
1µF
C7
MIC2103/04
VDD/PVDD
AGND
BST
100.00
1000.00
10000.00
R20 (k Ohm)
Figure 3. Switching Frequency vs. R20
V
IN
2.2µF
x3
C2, C3, C4
R19
FREQ
R20
PGND
FB
VIN
SW
CS
.
Figure 2. Switching Frequency Adjustment
The following formula gives the estimated switching
frequency:
f
SW
_
ADJ
½
f
O
R
20
R
19
R
20
(Eq. 4)
Where f
O
= Switching Frequency when R19 is 100k
and R20 being open, f
O
is typically 600kHz at 12V
input voltage. For more precise setting, it is
recommended to use the following graph:
October 2012
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M9999-100512
Micrel, Inc.
MIC2103/04 10A Evaluation Board
MIC2103/04 0.8V to 5V/10A Evaluation Board Typical Characteristics
100
90
80
Efficiency (V
IN
=12V)
vs. Output Current (MIC2103)
5.0V
3.3V
2.5V
1.8V
1.2V
0.8V
100
90
80
Efficiency (V
IN
= 18V)
vs. Output Current (MIC2103)
5.0V
3.3V
2.5V
1.8V
1.2V
0.8V
100
90
80
Efficiency (V
IN
= 24V)
vs. Output Current (MIC2103)
5.0V
3.3V
2.5V
1.8V
1.2V
0.8V
EFFICIENCY (%)
EFFICIENCY (%)
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0
1
2
3
4
5
6
7
8
70
60
50
40
30
20
10
0
0
1
2
3
4
5
6
7
8
70
60
50
40
30
20
f
SW
= 200kHz (CCM)
f
SW
= 200kHz (CCM)
9 10 11 12 13 14
10
0
0
1
2
3
4
5
6
f
SW
= 200kHz (CCM)
9 10 11 12 13 14
7 8
9 10 11 12 13 14
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
100
90
80
Efficiency (V
IN
= 38V)
vs. Output Current (MIC2103)
5.0V
3.3V
2.5V
1.8V
1.2V
0.8V
100
90
80
Efficiency (V
IN
= 48V)
vs. Output Current (MIC2103)
5.0V
3.3V
2.5V
1.8V
1.2V
0.8V
100
90
80
Efficiency (V
IN
= 75V)
vs. Output Current (MIC2103)
EFFICIENCY (%)
EFFICIENCY (%)
60
50
40
30
20
10
0
0
1
2
3
4
5
6
7
8
f
SW
= 200kHz (CCM)
60
50
40
30
20
10
0
0
1
2
3
4
5
6
EFFICIENCY (%)
70
70
70
60
50
40
30
20
5.0V
3.3V
2.5V
1.8V
1.2V
0.8V
f
SW
= 200kHz (CCM)
10
0
0
1
2
3
4
5
f
SW
= 200kHz (CCM)
9 10 11 12 13 14
7
8
9 10 11 12 13 14
6
7
8
9 10 11 12 13 14
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
October 2012
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M9999-100512
Micrel, Inc.
MIC2103/04 10A Evaluation Board
MIC2103/04 0.8V to 5V/10A Evaluation Board Typical Characteristics (Continued)
100
90
80
Efficiency (V
IN
=12V)
vs. Output Current (MIC2104)
5.0V
3.3V
2.5V
1.8V
1.2V
0.8V
100
90
80
Efficiency (V
IN
= 18V)
vs. Output Current (MIC2104)
5.0V
3.3V
2.5V
1.8V
1.2V
0.8V
100
90
80
Efficiency (V
IN
= 24V)
vs. Output Current (MIC2104)
5.0V
3.3V
2.5V
1.8V
1.2V
0.8V
EFFICIENCY (%)
70
60
50
40
30
20
60
50
40
30
20
10
0
0
1
2
3
4
5
6
7
8
EFFICIENCY (%)
EFFICIENCY (%)
70
70
60
50
40
30
20
f
SW
= 200kHz
9 10 11 12 13 14
10
0
0
1
2
3
4
5
6
7
8
f
sw
= 200kHz
9 10 11 12 13 14
10
0
0
1
2
3
4
5
6
7
8
f
SW
= 200kHz
9 10 11 12 13 14
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
100
90
80
Efficiency (V
IN
= 38V)
vs. Output Current (MIC2104)
100
90
Efficiency (V
IN
= 48V)
vs. Output Current (MIC2104)
5.0V
3.3V
2.5V
1.8V
1.2V
0.8V
100
90
80
Efficiency (V
IN
= 75V)
vs. Output Current (MIC2104)
EFFICIENCY (%)
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0
1
2
3
4
5
6
7
8
70
60
50
40
30
20
EFFICIENCY (%)
5.0V
3.3V
2.5V
1.8V
1.2V
0.8V
80
70
60
50
40
30
20
10
5.0V
3.3V
2.5V
1.8V
1.2V
0.8V
f
SW
= 200kHz
9 10 11 12 13 14
10
0
0
1
2
3
4
5
6
7
8
f
SW
= 200kHz
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14
f
SW
= 200kHz
9 10 11 12 13 14
0
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
Die Temperature* (V
IN
= 12V)
vs. Output Current
140
Die Temperature* (V
IN
= 48V)
vs. Output Current
140
DIE TEMPERATURE (°C)
DIE TEMPERATURE (°C)
120
100
80
60
40
20
10
140
120
100
80
60
40
20
0
Die Temperature* (V
IN
= 75V)
vs. Output Current
DIE TEMPERATURE (°C)
120
100
80
60
40
V
IN
= 12V
20
0
0
1
2
3
4
5
6
V
OUT
= 5.0V
f
SW
= 200kHz
7
8
9
`
V
IN
= 48V
V
OUT
= 5.0V
f
SW
= 200kHz
V
IN
= 75V
V
OUT
= 5.0V
f
SW
= 200kHz
0
0
1
2
3
4
5
6
7
8
9
10
OUTPUT CURRENT (A)
0
1
2
3
4
5
6
7
8
9 10
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
Die Temperature* :
The temperature measurement was taken at the hottest point on the MIC2103/04 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.
October 2012
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M9999-100512
Embedded System
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