MIC3203/MIC3203-1
Evaluation Board
High Brightness LED Driver Controller
with High-Side Current Sense
General Description
The MIC3203/MIC3203-1 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
MIC3203/MIC3203-1 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 4.5V to 42V
input voltage range, and controls an external power
MOSFET to drive high current LEDs. When the input
voltage approaches and crosses UVLO threshold, the
internal 5V VCC is regulated and the external 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 external 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
external 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.
Requirements
This board needs a single bench power source
adjustable over the input voltage of 4.5V < V
IN
< 42V that
can provide at least 1A of current. The loads can either
be active (electronic load) 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.
Under extreme load conditions input transients can be
quite large if long test leads are used. In such cases a
100µF, 63V electrolytic capacitor is needed at the V
IN
terminals to prevent over voltage damage to the IC.
Getting Started
1.
Connect V
IN
supply to the input terminals V
IN
and GND.
With the output of this supply
disabled, set its voltage to the desired input test
voltage (4.5V < V
IN
< 42V). 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
+V
IN
input terminal to accurately measure input
current.
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 current sense resistor R
CS
i.e.,
200mΩ.
Selecting the sense resistor refers to the table
given in data sheet application sub-section.
2.
Enable the input supply.
By default, the
controller is enabled when the input voltage
approaches UVLO threshold and crosses 5V,
the internal 5V VCC is regulated and the
external MOSFET is turned on if EN pin and
DIM pin are high. To use the EN and DIM
functions of the MIC3203/MIC3203-1, a test
point is provided for each of them.
Ordering Information
Part Number
MIC3203YM EV
MIC3203-1YM EV
Description
Evaluation board with
MIC3203YM device
Evaluation board with
MIC3203-1YM device
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (
408
) 944-0800 • fax + 1 (408) 474-1000 •
http://www.micrel.com
January 2011
M9999-011311-B
Micrel, Inc.
MIC3203/3203-1 Evaluation Board
R
CS
is given by
1 V
CS(MAX )
+ V
CS(MIN)
x(
)
Error! Bookmark not
2
I
LED
defined.
I
LED
is LED current required to set.
For V
CS(MAX)
and V
CS(MIN) ,
refers to electrical
characteristics table in the data sheet.
To calculate the frequency spread across input supply:
R
CS
=
F
SW
=
(V
D
+I
LED
×R
CS
+ V
LED
) ×(V
IN
-
I
LED
×R
CS
-
V
LED
)
L ×
Δ
I
L
×(V
D
+ V
IN
)
Other Features
EN Input
The EN pin provides a logic level control of the output
and the voltage has to be 2.0V or higher to enable the
current regulator. The output stage is gated by the DIM
pin. When the EN pin is pulled low, the regulator goes to
off state and the supply current of the device is reduced
to below 1µA. In the off state, the output drive is placed
in a "tri-state" condition, where MOSFET is in an “off” or
non-conducting state. Do not drive the EN pin above the
supply voltage.
DIM Input
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
voltage has to be 2.0V or higher. DIM low disables the
output, regardless of EN high state.
Current Sense Input
The CS pin provides the high-side current sense to set
the LED current with an external sense resistor.
A sense resistor R
CS
is placed between V
IN
and LED+
terminal.
The current flowing through LED is sensed and current
feedback is provided to the hysteretic step-down
regulator.
Δ
I
L
=
V
CS(MAX )
-
V
CS(MIN)
R
CS
where : V
D
is Schottky diode forward drop
V
LED
is total LEDs voltage drop
V
IN
is input voltage
I
LED
is average LED current
According to the above equation, choose the inductor to
make the operating frequency no higher than 1.5MHz.
Refer to the datasheet “Application Information” for more
information on components selection guidelines.
Frequency Dithering
The MIC3203 is designed to modulate the V
CS(MAX)
with
amplitude ±6mV by a pseudo random generator to
generate the ±12% of the switching frequency dithering
to spread the frequency spectrum over a wider range
and reduce the EMI noise peaks
The MIC3203-1 is non-dithering version of the MIC3203.
January 2011
2
M9999-011311-B
Micrel, Inc.
Evaluation Board Performance
Efficiency
vs. Input Voltage
100
MIC3203/3203-1 Evaluation Board
Efficiency
vs Input Voltage
100
90
90
EFFICIENCY (%)
EFFICIENCY (%)
80
4LED
6LED
8LED
70
10LED
80
4LED
6LED
70
8LED
10LED
L=68µH
ILED=1A
L=150µH
ILED=1A
60
0
5
10
15
20
25
30
35
40
45
60
0
5
10
15 20 25 30
INPUT VOLTAGE (V)
35
40
45
INPUT VOLTAGE (V)
Normalized LED Currents
vs. Input Voltage
1.03
Normalized LED Currents
vs Input Voltage
1.03
L=150µH
ILED=1A
NORMALIZED LED CURRENTS (A)
NORMALIZED LED CURRENTS (A)
L=68µH
ILED=1A
1.02
1.02
1.01
1LED
1
2LED
4LED
6LED
10LED
8LED
1.01
1
1LED
0.99
2LED
0.98
4LED
0.99
0.98
6LED
8LED
10LED
0.97
0
5
10
15
20
25
30
35
40
45
0.97
0
5
10
15
20
25
30
35
40
45
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
* With regards to V
IN
January 2011
3
M9999-011311-B
Micrel, Inc.
MIC3203/3203-1 Evaluation Board
Evaluation Board Schematic
Notes:
1.
2.
If bulk capacitor on input rail is away (4 inches or more) from the MIC3203/MIC3203-1, install the 100µF bulk capacitor near V
IN
.
Source impedance should be as low as 10mΩ.
January 2011
4
M9999-011311-B
Micrel, Inc.
MIC3203/3203-1 Evaluation Board
Bill of Materials
Item
C1,
C2, C5
Part Number
12105C475KAZ2A
GRM32ER71H475KA88L
C3225X7S1H475M
08053D105KAT2A
C3
GRM21BR71E105KA99L
C2012X7R1E105K
C4
(Open) 08055A271JAT2A
(Open) GRM2165C2A271JA01D
SK36-TP
D1
L1
M1
R1
R2, R3
R4
R5
R6
SK36
SK36-7-F
SLF10145T-680M1R2
FDS5672
CSR 1/2 0.2 1% I
CRCW08051003FKEA
CRCW08050000FKEA
(Open) CRCW08052R20FKEA
CRCW08051002FKEA
MIC3203YM
U1
MIC3203-1YM
Notes:
1. AVX: www.avx.com
2. Murata: www.murata.com
3. TDK: www.tdk.com
4. MCC: www.mccsemi.com
5. Fairchild: www.fairchildsemi.com
6. Sumida Tel: www.sumida.com
7. Stackpole Electronics: www.seielect.com
8. Vishay: www.vishay.com
9.
Micrel, Inc.: www.micrel.com
Manufacturer
AVX
(1)
Murata
(2)
TDK
(3)
AVX
(1)
Murata
(2)
TDK
(3)
AVX
(1)
(2)
Description
4.7µF/50V, Ceramic Capacitor, X7R, Size 1210
1µF/25V, Ceramic Capacitor, X5R, Size 0805
1µF/25V, Ceramic Capacitor, X7R, Size 0805
1µF/25V, Ceramic Capacitor, X7R, Size 0805
270pF/50V, Ceramic Capacitor NPO, Size 0805
270pF/100V, Ceramic Capacitor NPO, Size 0805
60V, 3A, SMC, Schottky Diode
68µH, 1.2A, SMT, Power Inductor
MOSFET, N-CH, 60V, SO-8
0.2Ω Resistor, 1/2W, 1%, Size 1206
100kΩ Resistor, 1%, Size 0805
0
Ω
Resistor, 1%, Size 0805
2.2
Ω
Resistor, 1%, Size 0805
10kΩ Resistor, 1%, Size 0805
High Brightness LED Driver Controller with
High-Side Current Sense-Frequency Dithering
Qty.
3
1
Murata
1
MCC
(4)
Fairchild
(5)
Diode
(10)
SUMIDA
(6)
Fairchild
(11)
1
1
1
1
2
1
1
1
Stackpole
(7)
Electronics Inc
Vishay
(8)
Vishay
Vishay
(8)
(8)
Vishay
(8)
Micrel, Inc.
(9)
High Brightness LED Driver Controller with
High-Side Current Sense-Frequency Non-
Dithering
1
January 2011
5
M9999-011311-B
stm32/stm8
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