ST STEVAL-ILL009V1 Installation and operating instructions

September 2008 Rev 2 1/40
AN2531
Application note
Generating multicolor light using RGB LEDs
Introduction
The new high power and brightness RGB LEDs are going to be used in many different
lighting applications as backlighting, general lighting systems, traffic signals, automotive
lighting, advertising signs, etc. They are becoming popular mainly because it is possible to
generate an easy multicolor light with special lighting effects and their brightness can be
easy changed. On top of this, their long lifetime and small size make them the light source of
the future.
This document describes how to drive RGB LEDs, how to calculate a power dissipation,
how to design an over temperature protection, how to use a software PWM modulation and
why over voltage protection should be implemented for this kind of application.
STEVAL-ILL009V1 reference board shown in Figure 1 was developed in order to
demonstrate this design concept. This board was designed for driving super high brightness
multicolor RGB LEDs with current up to 700 mA per LED. The LED brightness and color can
be very easy changed by potentiometers and an automatic color change mode continuously
modulates the color of the LED to generate multicolor light. The LED over temperature
protection is designed on this board and therefore the power delivered to the LED can be
automatically limited to prevent LED overheating.
The STEVAL-ILL009V1 is a mother board assembled without LEDs. To evaluate light effect
features, it is necessary to order a load board (additional board with assembled RGB LEDs).
Two load boards are available for easy performance evaluation. The first one with the
OSTAR
®
Projection Module (refer to Chapter 12, point 1) has ordering code STEVAL-
ILL009V3 and the second one with the Golden DRAGON
®
LEDs (refer to Chapter 12,
point 2) has ordering code STEVAL-ILL009V4. All technical information about these
reference boards such as bill of materials, schematics, software, temperature protection and
so on are described in the sections below.
Note: A new reference board STEVAL-ILL009V5 was designed in order to replace the former
STEVAL-ILL009V1. The main reason why the new board was developed is to demonstrate
a new DC/DC converter capabilities using the ST1S10 and new improved LED drivers
STP04CM05 and STP08CP05. Thanks to the ST1S10 the size of the inductor is extremely
decreased, efficiency improved and board size significantly reduced. The STEVAL-
ILL009V5 reference design is described in Chapter 9.
Figure 1. STEVAL-ILL009V1 reference board
www.st.com

Contents AN2531
2/40
Contents
1 Driving concept for RGB LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 How to drive many LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3 How to set high current for LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4 Color control - software modulation . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5 Power dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6 Over voltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.2 Type of solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
7 LED temperature protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
8 STEVAL-ILL009V1 reference board . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
8.1 General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
8.2 Getting started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
8.3 Schematic description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
8.4 Bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
8.5 Design calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8.5.1 LED supply voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8.5.2 Temperature protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8.5.3 SW PWM frequency calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
8.6 Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
9 STEVAL-ILL009V5 reference board . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
9.1 STEVAL-ILL009V5 schematic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 31
9.2 Bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
10 STEVAL-ILL009V3 load board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
10.1 Schematic description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
10.2 Bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

AN2531 Contents
3/40
11 STEVAL-ILL009V4 load board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
11.1 Schematic description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
11.2 Bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
12 Reference and related materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
13 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

List of tables AN2531
4/40
List of tables
Table 1. BOM - STEVAL-ILL009V1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Table 2. Temperature limit setting using STLM20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Table 3. Temperature limit setting using NTC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Table 4. STEVAL-ILL009V5 bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Table 5. STEVAL-ILL009V3 bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Table 6. STEVAL-ILL009V4 bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Table 7. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

AN2531 List of figures
5/40
List of figures
Figure 1. STEVAL-ILL009V1 reference board. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Figure 2. Driving concept for RGB LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Figure 3. LED driver connection - serial configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Figure 4. LED driver connection - parallel configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Figure 5. Common drain configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Figure 6. Software brightness modulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Figure 7. RGB LED configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Figure 8. Over voltage on STP04CM596. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Figure 9. Possible over voltage protections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Figure 10. Temperature protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Figure 11. Components position on the STEVAL-ILL009V1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Figure 12. STEVAL-ILL009V1 schematics - LED drivers part. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Figure 13. STEVAL-ILL009V1 power sources schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Figure 14. Send data time diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Figure 15. Main program flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Figure 16. Blink function flowchart - first part. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Figure 17. Blink function flowchart - second part. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Figure 18. Manual color modulation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Figure 19. Blink function flowchart - third part . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Figure 20. STEVAL-ILL009V5 reference board. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Figure 21. STEVAL-ILL009V5 power sources schematic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Figure 22. STEVAL-ILL009V3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Figure 23. STEVAL-ILL009V3 schematic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Figure 24. STEVAL-ILL009V4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Figure 25. STEVAL-ILL009V4 schematic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Driving concept for RGB LEDs AN2531
6/40
1 Driving concept for RGB LEDs
RGB refers to the three primary colors, red, green, and blue. Different colors can be
generated by controlling the power to each LED. In this application, the microcontroller
provides three software PWM signals (principle is described below in Chapter 4) for LED
drivers STP04CM596 so the color can be regulated.
The STP04CM596 is a high-power LED driver with 4-bit shift register designed for power
LED applications. In the output stage, four regulated current sources provide 80-500 mA
constant current to drive high power LEDs.
Figure 2 shows the driving concept for RGB LEDs using an STP04CM596 LED driver. The
LED supply voltage is connected to anodes of RGB LED and LEDs cathodes are connected
to the ground through constant current sources. The supply voltage value is very important
due to the power dissipation on drivers (detail explanation is described in Chapter 5).
The value of the constant current is set by only one external resistor for all the four driver
channels. The control unit in this application is a microcontroller, which sends data through
serial peripheral interface (SPI) to the shift registers inside STP04CM596. The data are
shifted bit by bit to the next drivers in a cascade with falling edge of the clock frequency (the
maximum communication frequency for this drivers is 25 MHz). When all data are
transmitted to the drivers through SPI, the micro sets latch input terminal (LE) pin “log 1" to
rewrite the data to the storage registers and to turn on or off the LEDs. More details on
timings and features are available in Application Note AN2141 (refer to Chapter 12, point 3)
and Datasheet of the STP04CM596 (refer to Chapter 12, point 4).
Temperature protection is designed in order to protect LEDs and increase their lifetime.
A sensor (STLM20) is assembled close to the RGB LEDs and informs the microcontroller
about RGB LED temperature. If the temperature is above its limit, the microcontroller
decreases LED brightness (LED power) through PWM signal.
An easy and user friendly hardware interface (potentiometers and buttons) was designed to
demonstrate features such as color set, brightness regulation, mode changes, etc.
Figure 2. Driving concept for RGB LEDs
AM00285
IC supply
voltage
CONTROL PANEL
MODE COLOR
Micro SPI
STP04CM596
Constant
current
Control
and
logic
part
I - reg.
LED supply
voltage Temperature sensor
Full color pixel

AN2531 How to drive many LEDs
7/40
2 How to drive many LEDs
In several applications not only one RGB LED, but many of them must be driven. There are
at least two possible ways to drive many RGB LEDs using the STP04CM596 LED driver,
depending on the specific lighting application.
If the request is to control each RGB LED independently, a serial configuration (drivers in
cascade connection) must be used as shown in Figure 3. The data are sent through all LED
drivers via the SPI and then latched to the outputs. The main advantage is that current in
each channel can be regulated by software PWM modulation, which in fact means color
control of each RGB LED. The disadvantage of this solution is lower PWM resolution for
a higher number of RGB LEDs, because it needs time to send data to all drivers. More
information about this principle is described in Chapter 4: Color control - software
modulation.
If the request is to build up a high power light with many LEDs of the same color, drivers can
be connected in parallel as shown in Figure 4. Main advantages are a simpler solution and
better PWM resolution, because only four bits are sent through the SPI and it takes a short
time. Color is also regulated by software PWM signals as described in Chapter 4.
Note: It is also possible to mix serial and parallel configurations in order to provide severaldifferent
colors with high lighting power. For example, two different colors using 10 RGB LEDs can be
implemented using two STP04CM596 connected in series and five such blocks connected
in parallel.
Figure 3. LED driver connection - serial configuration
AM00286
Micro
SPI
LED supply
voltage
STP04CM596
Control
and
logic
part
STP04CM596
Control
and
logic
part
Serial connection
SPI

How to drive many LEDs AN2531
8/40
Figure 4. LED driver connection - parallel configuration
AM00287
Micro
SPI
LED supply
voltage
STP04CM596
Control
and
logic
part
STP04CM596
Control
and
logic
part
Parallel connection

AN2531 How to set high current for LEDs
9/40
3 How to set high current for LEDs
The STP04CM596 is focused on driving high brightness and power LEDs and its output
constant current can be set between 80 and 500 mA. In case a LED with even higher
current is used, there is still a solution to control such LED using the STP04CM596. Thanks
to a common drain configuration, the outputs can be connected together as shown in
Figure 5. This increases the performance and current capability of this driver. This
configuration allows driving the whole range of HB LEDs available on the market. For
example, this principle is also used in the STEVAL-ILL009V1 presented in this application
note, because the board has maximum current capability of 700 mA (2 channels x 350 mA).
Figure 5. Common drain configuration
AM00288
STP04CM596 Rext
I-REG
Vo
Vo
Vo
Vf+ Vc

Color control - software modulation AN2531
10/40
4 Color control - software modulation
Software control modulation allows adjusting power to each channel of the STP04CM596
driver (i.e. LED brightness). Figure 6 explains the principle showing an example of how to
set an 8% duty cycle for red, 28% duty cycle for blue, 6% duty cycle for green and 98% duty
cycle for a fourth LED. For one complete dimming cycle, the microcontroller sends a certain
number of “0”s and “1”s to each LED. First, the microcontroller sends four bits in “logical 1"
(i.e. 1111b or Fh) to the driver in order to turn ON all the output channels. Then
microcontroller sends the same data (1111) until an output should be turned OFF
(depending on desired preset color). (Each bit of the 4-bit frame controlling its
corresponding output.) In this example, it is output 3 with green LED (6% duty cycle
required). From that moment, the microcontroller keeps sending 1101. In the next step the
output 1 with red LED (8% duty cycle) should be turned OFF and so data frame changes to
0101. This frame is sent until output 2 with blue LED (28% duty cycle) should be turned OFF
and when the frame 0001 is used. Finally, the output 4 with another LED (usually second
green LED) is turned OFF with 98% duty cycle, which means than 0000 is being sent until
maximum time for one cycle is reached. After that, the entire period for all outputs can start
again.
Figure 6. Software brightness modulation
The resolution of the LED dimming defines how many steps are possible to change the duty
cycle from 0% to 100% (e.g. 6-bit means 64 steps; 7-bit means 128 steps and so on). It is
obvious that it is preferred to design the control signal with a resolution as high as possible,
but several limitations should be taken into account. Limitations concern mainly the speed of
the serial communication interface inside the microcontroller (SPI) and the general
calculation power of the microcontroller. First, the general LED frequency should be
selected. This value is recommended to be above 100 Hz in order to avoid flickering as at
AM00289
DATA
Output 1
Output 2
Output 3
Output 4 98 % duty cycle
1111 1111 or new data1101 0101 0001 0000
T SW_PWM
LEVELS
6 % duty cycle
T SEND_DATA
8 % duty cycle
28 duty cycle
t
t
t
t

AN2531 Color control - software modulation
11/40
100 Hz and above it is not detected by the human eye and is considered as a stable light.
Using Equation 1 and Equation 2, the resolution can be obtained as shown in Equation 3.
Equation 1
Equation 2
Equation 3
In order to have a good resolution, the time for sending data (t
SEND_DATA
) must be as short
as possible. In an ideal case, this time takes into account the number of sent bits and the
speed of the SPI clock (one bit is sent during one SPI period). As described in Figure 6, the
number of sent bits corresponds to the number of driven LEDs, therefore in Equation 4, the
number of driven LEDs is the same as number of bits sent (BITS = LEDS).
Equation 4
The maximum number of used LEDs is (assumption BITS = LEDS):
Equation 5
Note: The above calculation is only valid only when the data are sent to the driver through the SPI
without any delay. This means the data (BYTES) are sent thought the SPI and at the end of
this communication the next data (BYTES) are immediately sent, etc.
In case the data are sent through the SPI and then microcontroller executes some other
instructions (checking temperature, checking ADC in order to set next PWM signal,etc.), the
period (t
SEND_DATA
) for sending data is longer and it decreases the real maximum
resolution.
SW_PWM
SW_PWM
f1
t=
LEVELS
t
t
SW_PWM
SEND_DATA
=
SEND_DATASW_PWM
tf 1
LEVELS × =
BITSt
fBITS
t
SPI_CLK
SPI_CLK
SEND_DATA
×==
LEVELStf 1
LEDS
SPI_CLKSW_PWM
××
=

Power dissipation AN2531
12/40
5 Power dissipation
The maximum power dissipation can be calculated with ambient temperature and thermal
resistance of the chip. The thermal resistance depends on the type of package and can be
found together with maximum junction temperature in the datasheet. The maximum
allowable power consumption without a heatsink is calculated as follows:
Equation 6
P
d max
……. maximum power dissipation [W]
T
a
……….…. ambient temperature [°C]
T
j max
……... maximum junction temperature [°C]
R
thja
………. junction to ambient thermal resistance [°C/W].
A high power RGB LED is in fact driven in linear mode with STP LED driver family. The
current flowing through each channel of the LED driver is constant and so power dissipation
depends on the voltage on each channel, which is the difference between the supply voltage
(DC bus) and the forward voltage drop on the LEDs. Therefore it is recommended to keep
the supply voltage as low as possible, but always above the maximum LED forward voltage.
Figure 7 shows the RGB LED connection to the driver. Total power dissipation in this case is
calculated using the following equation:
Equation 7
P
tot
……….…….power dissipation on chip [W]
I…………………constant LED current set by external resistor [A]
V
c
………………LED supply voltage [V]
V
f_red
………….red LED forward voltage [V]
V
f_blue
….…….blue LED forward voltage [V]
V
f_green
……....green LED forward voltage [V].
thja
ajmax
dmax
RT–T
P=
()( )
(
)
f_greenCf_blueCf_redCtot
V–VI*2V–V*IV–V*IP ++=

AN2531 Power dissipation
13/40
Figure 7. RGB LED configuration
Note: Red, blue and green LEDs have different forward voltages (refer to Chapter 2). In general,
the red LED has a lower forward voltage and therefore the power dissipation on the red LED
channel is the highest. There is quite simple way to decrease this power dissipation by using
a serial resistor with the red LED. Calculation example is shown in Section 10.1 and 11.1.
AM00290
STP04CM596 Rext
I-REG
Vo
Vo
Vo
Vf_red Vc
Vf_blue
Vf_green
Vo
Vf_green

Over voltage protection AN2531
14/40
6 Over voltage protection
6.1 Description
The maximum voltage on the output channels of STP04CM596 is 16 V. Any wire or PCB
track connection between LEDs and STP04CM596 driverpresents a parasitic inductance as
shown in Figure 8. This parasitic inductance produces voltage spikes on the outputs of the
driver when the driver is turning off the LEDs and it can be dangerous for the STP04CM596
as it can exceed the maximum output voltage rating. Generally, higher current and higher
parasitic inductance (long cable) means higher voltage peaks. Therefore over voltage
protection is very important for high brightness LEDs in case of long connections between
the driver and LEDs.
Figure 8. Over voltage on STP04CM596
AM00291
SPI
STP04CM596
Control
and
logic
part
4 V at 3 A Temperature sensor
Full color pixel
Over voltage
Maximum output
voltage 16 V
Lp
Lp
Lp Lp

AN2531 Over voltage protection
15/40
6.2 Type of solutions
Figure 9 shows possible types of over voltage protection. The first solution proposes
a Transil™ or a Zener diode connected between each channel of the LED driver and
ground. Unidirectional Transils with break down voltage lower than 16 V such as the SMAJ
Transil family (refer to Chapter 12, point 5) can be used.
The second solution proposes to use a standard diode or Schottky diode as a freewheeling
diode. Diodes are connected between the LED supply voltage (DC bus) and driver's channel
and so limit the voltage on the channels.
The third solution is the most cost effective and uses only a single Zener diode which
protects all channels. It can be used only if the connection between the LED driver and LED
cathodes is a quite short and if the connection between LED supply voltage and anodes is
long. This protection limits over voltage peaks on LED anodes.
Figure 9. Possible over voltage protections
AM00292
SPI
STP04CM596
Control
and
logic
part
4 V at 3 A Temperature sensor
Full color pixel
Maximum output
voltage 16 V
Lp
Lp
Lp Lp
Lp
3D
21
Transil Zener
diode
4
Zener
diode

LED temperature protection AN2531
16/40
7 LED temperature protection
The STEVAL-009V1 was designed for high power RGB LEDs with a nominal power even
higher then ten watts. As the lifetime of LEDs significantly decreases with temperature, the
proper temperature management must be implemented to check and limit its maximum
values.
Two different temperature protections are used in this design as shown in Figure 10 - the
STLM20 temperature sensor and NTC (negative temperature coefficient) resistor. The
STEVAL-ILL009V3 uses an NTC resistor directly assembled on the aluminum LED board
(OSTAR projection module). The STEVAL-ILL009V4 has assembled the STLM20
temperature sensor in the middle of LEDs on the PCB. The microcontroller checks the
voltage from the sensors and sets the correct output PWM signal on the OE pin of the LED
drivers. The microcontroller can increase the duty cycle of the PWM signal (0% duty cycle is
max bright and 100% duty cycle is no bright) or can turn OFF the RGB LED if over
temperature occurs. Software implementation is up to designers. Temperature protection
calculation using the STLM20 or NTC is presented in Chapter 8.5.2.
Figure 10. Temperature protection
AM00293
STEVAL - ILL009V4 STEVAL - ILL009V3
STLM20 Micro ADC
Vc
R
NTC

AN2531 STEVAL-ILL009V1 reference board
17/40
8 STEVAL-ILL009V1 reference board
STEVAL-ILL009V1 reference board shown in Figure 1 was designed to demonstrate how
high power and high brightness RGB LEDs can be driven and to confirm the principles
described in the paragraphs above.
This board has the following main features:
● Different LEDs as a load can be used (additional boards connected through 30 pin
connector)
● 8 LEDs with 350 mA can be driven (e.g. Golden DRAGON module - STEVAL-
ILL009V4)
● 4 LEDs with 700 mA can be driven (e.g. OSTAR module - STEVAL-ILL009V3)
● LED over temperature protection using STLM20 or NTC resistor
● LED temperature limit set by software
● 3 A at 4 V DC/DC converter using L4973D3.3 for user friendly input (8 - 30 V)
● Color regulation (manual / auto)
● Brightness PWM regulation with 64 levels using OE pin (dimming all LEDs)
● Red, Green, Blue individual tuning
● White color preset mode
● LED frequency = 100 Hz
● 64 levels of brightness for each LED with software color control
● 262144 color variations (64 x 64 x 64)
● SW startup implemented (200 ms)
● Over voltage protection implemented using clamp Schottky diodes (BAT46)
● 6 different light MODES available
● Input over voltage protection done by Transil (SMAJ33A)
● Over temperature signalization
● I
CC
connector for SW evaluation and change.
8.1 General description
Figure 11 shows components position on the STEVAL-ILL009V1. On the left side there is
DC/DC converter with L4973D3.3 (ref. to Chapter 12, point 6) with power capability 3 A
at 4 V. The input voltage range is from 8 to 30 V and it is connected through input connector.
The L78L05 (ref. to Chapter 12, point 7) provides 5 V supply voltage for the microcontroller
and LED drivers (signal diode D8 is used to show connected power). Potentiometers P1 and
P2 are used to set brightness for all LEDs or tuning each of them separately. High power
RGB LEDs are driven by STP04CM596 and STP08CL596 is used to control signal LEDs
(D1-D7) which are implemented to show which of the several lighting modes is currently set.
30 pins load connector provides better flexibility, because different types of LEDs can be
connected to the same board. As an example two load boards with LEDs were designed -
STEVAL-ILL009V3 and STEVAL-ILL009V4.

STEVAL-ILL009V1 reference board AN2531
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Figure 11. Components position on the STEVAL-ILL009V1
8.2 Getting started
Getting started chapter briefly describes how to use the STEVAL-ILL009V1 as a step by
step guide in order to quickly start with the evaluation.
1. Connect LED board to the STEVAL-ILL009V1 reference board using the 30-pin load
connector2. STEVAL-ILL009V3 or STEVAL-ILL009V4 is LED boards.
2. Connect the supply voltage between 8 to 30 V on the board using J1 connector. The
power capability of the adapter must be higher then 14 W in order to have enough
energy for the application.
Note: The maximum channel current is set to 350 mA and so the LEDs and driver power
consumption is P
LEDout
= 4V x 0.35 mA x 8 = 11.2 W. The efficiency of the DC/DC converter
is approximately 80 % (P
LEDin
= 13.44 W). Considering the microcontroller and LED drivers
themselves must be also supplied (consumption is less than 0.5 W) the total consumption is
~14 W and therefore the power capability of the adapter must be higher then 14 W in order
to have enough energy for the application.
3. If the application is supplied, the green LED (D8) is lighted ON. It shows that there is
a supply voltage for the micro and the drivers. Also LED D5 is turned ON at the start-up
as the Automatic Color Control mode is set. Color automatically changes from blue to
green, green to red and red to blue. During this mode, the brightness of all LEDs can be
changed by potentiometer P2, but the function of the potentiometer P1 is disabled in
this mode.
4. Press the button (S2) to change the mode. The next mode is White Color Control
mode. LED D7 is turned ON. The brightness of all LEDs can be changed by
potentiometer P2 and the function of the potentiometer P1 is disabled in this mode.
5. Press the button (S2) to set the next mode. It is Red Color Control mode. In this mode
the brightness for the Red LED can be changed by potentiometer P1. There are 64
levels of brightness implemented. LED D1 is turned ON and the potentiometer P2 has
the same function as in point 4 - changing the brightness of all LEDs.
6. Press the button (S2) to set brightness for the Green LED. In this mode the brightness
for the Green LED can be changed by potentiometer P1. LED D2 is turned ON. The
potentiometer P2 has again the same function - changing the brightness of all LEDs.

AN2531 STEVAL-ILL009V1 reference board
19/40
Note: The brightness level of the RED light is set by previous mode and stored in the memory and
so the effect of the GREEN color is added to the RED one.
7. Press the button (S2) to set brightness for the Blue LED. In this mode the brightness for
the Blue LED can be changed by potentiometer P1. LED D3 is turned ON. The
potentiometer P2 has the same function - changing the brightness of all LEDs.
Note: The brightness levels of the RED and GREEN lights were set by previous modes and stored
in the memory and so the BLUE color is added to the RED and GREEN one.
8. The next mode (press button S2) is a Manual Color Control mode. It means the color
can be set as requested (going through predefined R-G-B curve) by the potentiometer
P1. LED D4 is turned ON. The potentiometer P2 has the same function - changing the
brightness of all LEDs.
9. During all modes described above, LED temperature control is implemented. If
over temperature occurs,the brightness of all LEDs is decreased by PWM signal on the
general OE/ pin (64 levels). The temperature is checked every 2.55 s and if it is still
above the limit, the duty cycle of PWM is further increased (OE/ pin has a “not output
enable” function, i.e. higher the duty cycle lower the brightness and vice versa). The
maximum temperature on the LED board is set to 50 °C for the Golden DRAGON LEDs
and 72 °C for the OSTAR Projection module. Note that the higher temperature limit can
be very easily set by software.
10. How to demonstrate over temperature protection? Set full brightness by
potentiometer P2 in White Color Control mode and wait approximately 3 minutes with
STEVAL-ILL009V3 (board with heatsink) or 1½ minutes with STEVAL-ILL009V4 (board
without heatsink). Temperature on LEDs is increased and if the over temperature is
detected, LED D6 is turned ON and the PWM duty cycle is increased and the
brightness decreased overcoming the potentiometer settings. The temperature of LED
board then should go down and if no over temperature is detected after the period of
time, the duty cycle is decreased again and normal operation is resumed.
8.3 Schematic description
The STEVAL-ILL009V1 reference board schematic diagram is shown in Figure 12 and
Figure 13. It is divided into two figures for easier understanding.
Figure 12 shows the components needed for LED driving. Resistors R2 and R3 set a
maximum constant current 350 mA for each output channel of the STP04CM596. Thanks to
this configuration, eight high brightness LEDs with the forward current 350 mA or 4 LEDs
with the forward current 700 mA (two outputs are in parallel) can be driven. The
STP08CL596 drives signal LED diodes with the constant current set to approximately 8 mA.
The signal coming from the NTC resistor or STLM20 temperature sensor assembled in
additional board (load boards) is filtered by a low-pass filter using capacitor C7 and resistor
R6.
Figure 13 shows the power sources for the application. A 12W DC-DC SMPS converter is
built on L4973D3.3 and design calculations are described in the datasheet (ref. to
Chapter 12, point 6) or in the AN938 (ref. to Chapter 12, point 8). The L78L05 is a linear
voltage regulator with output voltage set to 5 V used for microcontroller and drivers supply.

STEVAL-ILL009V1 reference board AN2531
20/40
Figure 12. STEVAL-ILL009V1 schematics - LED drivers part
VCC
Vd
Brightness
Color
LED0 - RED LED CONTROL LED1 - GREEN LED CONTROL LED2 - BLUE LED CONTROL LED3 - MANUAL COLOR CONTROL LED4 - AUTOMATIC COLOR CONTROL LED5 - OVER TEMPERATURE LED6 - WHITE COLOR
INFORMATION SIGNALS
LED0 LED1 LED2 LED3 LED4 LED5 LED6
PROTECTION
D13 B AT46
C5
100 nF
1
2
3 4
5 6
7
8
9
10
CONNECTOR1
S2
SWITCH
D18 B AT46
P2
R1 3 KΩ
VSS
1
2
RESET
3
AIN0
4
SCK
5
AIN2
6
MOSI
7
CLKIN
8PA7 9
ICCCLK 10
ICCDATA 11
NC 12 NC 13
PA2 14 PA1 15 PA0 16
IO1
ST7FLITE09
LI
D12 B AT46
R6 470
R1 1
R1 2
G1a
3
G1a
4
G1b
5
G1b
6
B1
7
B1
8
R2
9
R2
10
G2a
11
G2a
12
G2b
13
G2b
14
B2
15
B2
16
NC
17
NC
18
GND
19
GND
20
NC
21
Vo
22
NC
23
VCC
24
NC
25
NC
26
Vd
27
Vd
28
Vd
29
Vd
30
S1
Switch
/LE
5
OUT0
6
OUT1
7
NC
8NC 9
OUT2 10 OUT3 11
NC 12
/OE 13
SDO 14
R_ext 15
16
GND
1
GND
2
SDI
3
CLK
4
IO3
STP04CM596
GND
1
SDI
2
CLK
3
/LE
4
OUT0
5
OUT1
6
OUT2
7
OUT3
8
16
R-EXT 15
SDO 14
/OE 13
OUT7 12 OUT6 11 OUT5 10 OUT4 9
IO4
STP08CL596
10 KΩ
P1 R3
220
R2
220
R5 10 KΩ
/LE
5
OUT0
6
OUT1
7
NC
8NC 9
OUT2 10 OUT3 11
NC 12
/OE 13
SDO 14
R_ext 15
16
GND
1
GND
2
SDI
3
CLK
4
IO2
STP04CM596
D16 B AT46
C1 10 nF C1
R4
4.7 KΩ
C4 100 nF
D17 B AT46 D15 B AT46 D14 B AT46 D11 B AT46
AM00294
VCC
VCC
10 KΩ
VCC
ICC
VCC
VCC
VDD
VCC
VCC
VCC
VDD VDD
VDD
C7
100 nF
C6 10 nF
C2 100 nF C3 100 nF
CONNCON ECTOR2