MIC4724YMME Evaluation Board
3A Buck Regulator
General Description
The Micrel MIC4724 is a high efficiency PWM buck
(step-down) regulator that provides up to 3A of output
current. The MIC4724 operates at 2MHz and has
proprietary internal compensation that allows a closed
loop bandwidth of over 200kHz. The low on-
resistance internal P-Channel MOSFET of the
MIC4724 allows efficiencies up to 94%, reduces
external component count and eliminates the need for
an expensive external current sense resistor. The
MIC4724 operates from a 3V to 6V input and its
output is adjustable down to 1V. The devices can
operate with a maximum duty cycle of 100% for use
in low-dropout applications.
Requirements
The MIC4724 evaluation board requires an input
power source that is able to deliver greater than 3V at
over 3A. The output load can either be an active or
passive load.
Precautions
The evaluation board does not have reverse polarity
protection. Applying a negative voltage to the V
IN
terminal may damage the device. In addition, the
maximum operating voltage of the MIC4724
evaluation board is 6V. Exceeding 6.5V on the input
could damage the device.
For short circuit testing,
an additional input capacitor over 22µF is
required
when using the demo board. This is
preferably an electrolytic, but may be tantalum or
ceramic. The inductance of long test leads connecting
the supply voltage to the demo board can be over
1µH.
During a short circuit condition, the high peak currents
through the test leads may cause the input voltage to
spike high and exceed the absolute maximum rating
of 6V, possibly damaging the device.
Getting Started
1.
Connect an external supply to V
IN
terminal
. Apply desired input voltage to the
V
IN
and ground terminals of the evaluation
board, paying careful attention to polarity
and supply voltage (3V<V
IN
<6.5V). An
ammeter may be placed between the input
supply and the V
IN
terminal to the evaluation
board. Ensure the supply voltage is
monitored at the V
IN
terminal. The ammeter
and/or power lead resistance can reduce the
voltage supplied to the input.
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. Ensure the
output voltage is monitored at the V
OUT
terminal. The default output voltage is set to
1.8V. This can be adjusted by changing the
feedback resistors. See “Output Voltage.”
3.
Enable the MIC4724
. The enable pin is
connected to a pull up resistor. The
MIC4724 turns on when V
IN
exceeds the
UVLO threshold at the V
IN
pin. The MIC4724
may be turned off by shorting the pin to
ground or bringing the enable pin below the
enable threshold. An external connection on
the board provides easy access to the
enable pin.
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax 1 (408) 474-1000 • http://www.micrel.com
June 2008
M9999-062408-A
