MIC24056 Evaluation Board
12A, High-Efficiency, Synchronous DC/DC
Buck Regulator with HyperLight Load
®
SuperSwitcher II™
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.
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 T
ON
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
(1)
12A , 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.
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 VDD exceeds
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.
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.
Ordering Information
Part Number
MIC24056YJL EV
Description
12A HLL DC/DC Buck Regulator
Evaluation Board
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 +1 (408) 944-0800 • fax + 1 (408) 474-1000 •
http://www.micrel.com
February 11, 2013
Revision 1.0
Micrel, Inc.
MIC24056 Evaluation Board
Output Voltage
The output voltage on the MIC24056 evaluation board is
adjustable. It is set by adjusting the feedback resistors,
referring Equation 1:
V
OUT
R4
1
+
=
V
×
FB
R
BOTTOM
Eq. 1
where V
FB
= 0.8V and R
BOTTOM
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 R
BOTTOM
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 R
BOTTOM
and replacing it with the
values that yield the desired output voltage. Once R4 is
selected, R
BOTTOM
can be calculated using Equation 2:
R
BOTTOM
=
R4
×
V
V
OUT
FB
FB
−
V
Eq. 2
For V
FB
= 0.8V, as in Equation 3:
R
BOTTOM
=
R4
×
0.8V
V
OUT
−
0.8V
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.
February 11, 2013
2
Revision 1.0
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