MIC3203YM Evaluation Board User Guide

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 VCS(MAX) with respect to VIN, the external MOSFET is
turned off and the Schottky diode takes over and returns
the current to VIN. Then the current through inductor and
LEDs starts decreasing. When CS pin hits VCS(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 < VIN < 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 VIN
terminals to prevent over voltage damage to the IC.
Getting Started
1. Connect VIN supply to the input terminals VIN
and GND. With the output of this supply
disabled, set its voltage to the desired input test
voltage (4.5V < VIN < 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
+VIN 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 RCS 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
Description
MIC3203YM EV
Evaluation board with
MIC3203YM device
MIC3203-1YM EV
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
RCS is given by
Other Features
1 VCS(MAX ) + VCS(MIN)
x(
) Error! Bookmark not
2
ILED
defined.
ILED is LED current required to set.
For VCS(MAX) and VCS(MIN) , refers to electrical
characteristics table in the data sheet.
To calculate the frequency spread across input supply:
R CS =
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.
FSW =
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.
ΔIL =
VCS(MAX ) - VCS(MIN)
RCS
where : VD is Schottky diode forward drop
VLED is total LEDs voltage drop
VIN is input voltage
ILED 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.
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 RCS is placed between VIN and LED+
terminal.
The current flowing through LED is sensed and current
feedback is provided to the hysteretic step-down
regulator.
January 2011
(VD +ILED×RCS + VLED) ×(VIN - ILED×RCS - VLED)
L × ΔIL ×(VD + VIN)
Frequency Dithering
The MIC3203 is designed to modulate the VCS(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.
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Micrel, Inc.
MIC3203/3203-1 Evaluation Board
Evaluation Board Performance
Efficiency
vs Input Voltage
100
100
90
90
EFFICIENCY (%)
EFFICIENCY (%)
Efficiency
vs. Input Voltage
80
4LED
6LED
8LED
10LED
70
10
15
20
25
30
35
40
6LED
8LED
10LED
L=68µH
ILED=1A
60
60
5
4LED
70
L=150µH
ILED=1A
0
80
0
45
5
10
INPUT VOLTAGE (V)
35
40
45
Normalized LED Currents
vs Input Voltage
Normalized LED Currents
vs. Input Voltage
1.03
1.03
L=150µH
ILED=1A
NORMALIZED LED CURRENTS (A)
NORMALIZED LED CURRENTS (A)
15 20 25 30
INPUT VOLTAGE (V)
1.02
10LED
1.01
1LED
2LED
4LED
6LED
8LED
1
0.99
0.98
0.97
L=68µH
ILED=1A
1.02
1.01
1
1LED
0.99
2LED
4LED
0.98
6LED
8LED
10LED
0.97
0
5
10
15
20
25
30
35
40
45
0
INPUT VOLTAGE (V)
5
10
15
20
25
30
35
40
45
INPUT VOLTAGE (V)
* With regards to VIN
January 2011
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M9999-011311-B
Micrel, Inc.
MIC3203/3203-1 Evaluation Board
Evaluation Board Schematic
Notes:
1.
If bulk capacitor on input rail is away (4 inches or more) from the MIC3203/MIC3203-1, install the 100µF bulk capacitor near VIN.
2.
Source impedance should be as low as 10mΩ.
January 2011
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Micrel, Inc.
MIC3203/3203-1 Evaluation Board
Bill of Materials
Item
Part Number
12105C475KAZ2A
C1,
C2, C5
GRM32ER71H475KA88L
C3
TDK
1
1µF/25V, Ceramic Capacitor, X7R, Size 0805
AVX(1)
270pF/50V, Ceramic Capacitor NPO, Size 0805
(2)
Murata
Fairchild(5)
FDS5672
1µF/25V, Ceramic Capacitor, X7R, Size 0805
(3)
SK36
SLF10145T-680M1R2
M1
Murata
MCC(4)
SK36-7-F
3
1µF/25V, Ceramic Capacitor, X5R, Size 0805
(2)
SK36-TP
D1
4.7µF/50V, Ceramic Capacitor, X7R, Size 1210
(3)
AVX(1)
(Open) GRM2165C2A271JA01D
L1
Murata(2)
TDK
(Open) 08055A271JAT2A
Qty.
AVX
08053D105KAT2A
GRM21BR71E105KA99L
Description
(1)
C3225X7S1H475M
C2012X7R1E105K
C4
Manufacturer
270pF/100V, Ceramic Capacitor NPO, Size 0805
1
60V, 3A, SMC, Schottky Diode
1
68µH, 1.2A, SMT, Power Inductor
1
MOSFET, N-CH, 60V, SO-8
1
0.2Ω Resistor, 1/2W, 1%, Size 1206
1
(10)
Diode
SUMIDA(6)
Fairchild
(11)
R1
CSR 1/2 0.2 1% I
Stackpole
(7)
Electronics Inc
R2, R3
CRCW08051003FKEA
Vishay(8)
100kΩ Resistor, 1%, Size 0805
2
R4
CRCW08050000FKEA
Vishay(8)
0 Ω Resistor, 1%, Size 0805
1
R5
(Open) CRCW08052R20FKEA
Vishay(8)
2.2 Ω Resistor, 1%, Size 0805
1
(8)
10kΩ Resistor, 1%, Size 0805
1
R6
CRCW08051002FKEA
Vishay
High Brightness LED Driver Controller with
High-Side Current Sense-Frequency Dithering
MIC3203YM
Micrel, Inc.(9)
U1
MIC3203-1YM
High Brightness LED Driver Controller with
High-Side Current Sense-Frequency NonDithering
1
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
January 2011
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M9999-011311-B
Micrel, Inc.
MIC3203/3203-1 Evaluation Board
PCB Layout Recommendations
Top Assembly
Top Layer
Bottom Layer
January 2011
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M9999-011311-B
Micrel, Inc.
MIC3203/3203-1 Evaluation Board
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com
Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This
information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry,
specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual
property rights is granted by this document. Except as provided in Micrel’s terms and conditions of sale for such products, Micrel assumes no liability
whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or warranties
relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product
can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical
implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user.
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© 2010 Micrel, Incorporated.
January 2011
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M9999-011311-B