MIC24054 Evaluation Board
9A, High-Efficiency, Synchronous DC/DC
Buck Regulator with HyperLight Load
®
SuperSwitcher II™
General Description
The MIC24054 DC/DC synchronous buck regulator operates
over an input supply range of 4.5V to 19V and provides a
regulated output at up to 9A 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 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 MIC24054 uses 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 MIC24051 evaluation board
are a VIN supply of 5V to 19V, output voltage of 0.8V to 5V
(1)
at 6A , and 600kHz switching frequency.
Note:
1. Refer to the temperature curves shown in
Evaluation Board
Performance.
The typical minimum input voltage to maximum output
voltage conversion is limited by the maximum duty cycle.
®
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 MIC24054 evaluation board is 19V. The
evaluation board has two different layout designs, one
optimized for evaluation (Figure
1)
and another one
optimized for smaller footprint (Figure
2).
The evaluation
board is only populated with components shown in
schematic
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. Make sure 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 V
OUT
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 V
OUT
terminal. Make sure
that the output voltage is monitored at the V
OUT
terminal.
3.
Enable Input.
An EN connector is provided on the evaluation board
so that users can easily access the enable feature.
The output of the MIC24054 turns on when VDD
exceeds the UVLO threshold. The output of the
MIC24054 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 MIC24054 evaluation board requires only a single
power supply with at least 10A current capability. The
MIC24054 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 be either active or passive.
HyperLight Load is a registered trademark of Micrel, Inc.
Ordering Information
Part Number
MIC24054YJL EV
Description
9A HLL DC/DC Buck Regulator
Evaluation Board
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 1.1
Micrel, Inc.
MIC24054 Evaluation Board
Output Voltage
The output voltage on the MIC24054 evaluation board is
adjustable. It is set by adjusting the feedback resistors, as
shown in Equation 1:
V
OUT
=
V
FB
×
1
+
R
BOTTOM
R4
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, respectively. Leaving
R
BOTTOM
open gives a 0.8V output voltage. The output
voltage is set at the factory for a 1.8V output, but it can
easily be changed by moving the jumper to the
corresponding position to get an indicated voltage on the
board. If a desired voltage is not shown on the board, it is
easily changed by removing R
BOTTOM
and replacing it with
the values that yield the desired output voltage. After R4 is
selected, R
BOTTOM
can be calculated using Equation 2.
R
BOTTOM
=
R4
×
V
FB
V
OUT
−
V
FB
Eq. 2
For V
FB
= 0.8V:
R
BOTTOM
=
R4
×
0.8V
V
OUT
−
0.8V
Eq. 3
Do not set the output voltage to exceed 5V because of the
6.3V rating of the output capacitor and the limitation of the
line regulation. Please refer to the “Setting Output Voltage”
and “Ripple Injection” subsections of the “Application
Information” section of the MIC24054 datasheet for
detailed information.
February 11, 2013
2
Revision 1.1
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