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 2010
M9999-102810
General Description
The MIC3202/MIC3202-1 is a hysteretic step-down,
constant-current, High-Brightness LED (HB LED) driver.
It provides an ideal solution for interior/exterior lighting,
architectural and ambient lighting, LED bulbs, and other
general illumination applications.
This board enables the evaluation of the
MIC3202/MIC3202-1 for 1A LED current. The board is
optimized for ease of testing, with all the components on
a single side. The device operates from a 6V to 37V
input voltage range, and includes an integrated 1.0A
MOSFET. When the input voltage approaches and
crosses UVLO threshold, the internal 5V V
CC
is
regulated and the integrated MOSFET is turned on if EN
pin and DIM pin are high. The inductor current builds up
linearly. When the CS pin voltage hits the V
CS(MAX)
with
respect to V
IN
,
the internal
MOSFET is turned off and the
Schottky diode takes over and returns the current to V
IN
.
Then the current through inductor and LEDs starts
decreasing. When CS pin hits V
CS(MIN)
, the internal
MOSFET is turned on and the cycle repeats.
Since the control scheme does not need loop
compensation, it makes for a very simple design and
avoids problems of instability.
Datasheets and support documentation can be found on
Micrel’s web site at: www.micrel.com
.
Requirements
This board needs a single-bench power source
adjustable over the input voltage of 6V < V
IN
< 37V that
can provide at least 1A of current. The loads can either
be active (electronic load in CV mode) or passive
(LEDs) with the ability to dissipate the maximum load
power while keeping accessible surfaces ideally <70°C.
Precautions
There is no reverse input protection on this board. When
connecting the input sources, ensure that the correct
polarity is observed.
In the line transient condition, such as hot plug-in, an
electrolytic capacitor may be required at the VIN and
GND terminals in order to prevent IC damage from a
surge voltage.
Getting Started
1. Connect V
IN
supply to the input VIN and GND
terminals. With the output of this supply disabled,
set the supply voltage to the desired input test
voltage (6V < V
IN
< 37V). This supply voltage should
be monitored at the test boards input terminals to
allow voltage drops in the test cables (and ammeter
if used) to be accounted for. An ammeter can be
added inline with the +VIN input terminal to
accurately measure input current.
2. Connect the LEDs to the output terminals
between LED+ and LED−. This LED voltage drop
depends on manufacturer tolerance and number of
LEDs. The LED current can be measured using an
ammeter or current probe. A 4.7µF ceramic
capacitor helps to reduce the current ripple through
the LED. The LED current is set to 1A by a 200mΩ
current-sense resistor (R
CS
).
3. Enable the input supply. By default, the IC is
enabled when the input voltage crosses the VIN
threshold (4V) and the internal VCC regulator and
internal MOSFET are turned on with the EN and
DIM pins are high. To use the EN and DIM functions
of the MIC3202/MIC3202-1, a test point is provided
for each of them.
Ordering Information
Part Number Description
MIC3202YME EV MIC3202YME Evaluation Board
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