ST STEVAL-ILL009V1, Примечание к применению

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AN2531 How to drive many LEDs
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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 several different
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