MIC3202/MIC3202-1
Evaluation Board
High-Brightness LED Driver with Integrated
MOSFET and High-Side Current Sense
General Description Getting Started
1. Connect V supply to the input VIN and GND
The MIC3202/MIC3202-1 is a hysteretic step-down, IN
terminals. With the output of this supply disabled,
constant-current, High-Brightness LED (HB LED) driver.
set the supply voltage to the desired input test
It provides an ideal solution for interior/exterior lighting,
voltage (6V < V < 37V). This supply voltage should
IN
architectural and ambient lighting, LED bulbs, and other
be monitored at the test boards input terminals to
general illumination applications.
allow voltage drops in the test cables (and ammeter
This board enables the evaluation of the
if used) to be accounted for. An ammeter can be
MIC3202/MIC3202-1 for 1A LED current. The board is
added inline with the +VIN input terminal to
optimized for ease of testing, with all the components on
accurately measure input current.
a single side. The device operates from a 6V to 37V
2. Connect the LEDs to the output terminals
input voltage range, and includes an integrated 1.0A
between LED+ and LED. This LED voltage drop
MOSFET. When the input voltage approaches and
depends on manufacturer tolerance and number of
crosses UVLO threshold, the internal 5V V is
CC
LEDs. The LED current can be measured using an
regulated and the integrated MOSFET is turned on if EN
ammeter or current probe. A 4.7F ceramic
pin and DIM pin are high. The inductor current builds up
capacitor helps to reduce the current ripple through
linearly. When the CS pin voltage hits the V with
CS(MAX)
the LED. The LED current is set to 1A by a 200m
respect to V , the internal MOSFET is turned off and the
IN
current-sense resistor (R ).
Schottky diode takes over and returns the current to V . CS
IN
Then the current through inductor and LEDs starts
3. Enable the input supply. By default, the IC is
decreasing. When CS pin hits V , the internal
CS(MIN) enabled when the input voltage crosses the VIN
MOSFET is turned on and the cycle repeats.
threshold (4V) and the internal VCC regulator and
internal MOSFET are turned on with the EN and
Since the control scheme does not need loop
DIM pins are high. To use the EN and DIM functions
compensation, it makes for a very simple design and
of the MIC3202/MIC3202-1, a test point is provided
avoids problems of instability.
for each of them.
Datasheets and support documentation can be found on
Micrels web site at: www.micrel.com.
Ordering Information
Requirements
Part Number Description
This board needs a single-bench power source
adjustable over the input voltage of 6V < V < 37V that MIC3202YME EV MIC3202YME Evaluation Board
IN
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 <70C.
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.
Micrel Inc. 2180 Fortune Drive San Jose, CA 95131 USA tel +1 (408) 944-0800 fax + 1 (408) 474-1000 Micrel, Inc. MIC3202/MIC3202-1 Evaluation Board
Other Features
EN Input Frequency of Operation
The EN pin provides a logic level control of the output To calculate the frequency spread across input supply:
and the voltage has to be 2.0V or higher to enable the
current regulator. The output stage is gated by the DIM
(V +I R +V )(V -I R - V )
D LED CS LED IN LED CS LED
pin. When the EN pin is pulled low, the regulator goes to
F =
SW
L I (V +V )
off-state and the supply current of the device is reduced L D IN
to below 1A. Do not drive the EN pin above the supply
voltage.
V - V
CS(MAX) CS(MIN)
DIM Input
I =
L
R
CS
The DIM pin provides a logic level control for brightness
of the LED. A PWM input can be used to control the
brightness of LED. DIM high enables the output and its
where:
voltage has to be 2.0V or higher. DIM low disables the
V is Schottky diode forward drop
D
output, regardless of EN high-state.
V is total LEDs voltage drop
LED
Current-Sense Input
V is input voltage
IN
The CS pin provides the high-side current sense to set
I is average LED current
the LED current with an external sense resistor. LED
A sense resistor R is placed between V and LED+
CS IN
terminals.
According to the above equation, choose the inductor to
make the operating frequency no higher than 1MHz.
The current through LED is sensed by the sense resistor
(R ). The sensed voltage is fed back to the MIC3202 to
Refer to the datasheet Application Information for more
CS
regulate the LED current
information on components selection guidelines.
R is given by:
Frequency Dithering
CS
The MIC3202 is designed to modulate the V with
CS(MAX)
amplitude 6mV by a pseudo random generator to
V + V
1
CS(MAX) CS(MIN)
R = x( ) Error! generate the 12% of the switching frequency dithering.
CS
2 I
LED
This spreads the frequency spectrum over a wider range
Bookmark not defined.
and reduce the EMI noise peaks.
The MIC3202-1 is non-dithering version of the MIC3202.
I is LED current required to set.
LED
2
R () I (A) I R (W) Size (SMD)
CS LED
1.33 0.15 0.03 0603
0.56 0.35 0.07 0805
0.4 0.5 0.1 0805
0.28 0.7 0.137 0805
0.2 1.0 0.2 1206
For V and V refers to the Electrical
CS(MAX) CS(MIN)
Characteristics table.
October 2010 2 M9999-102810