STEVAL-ILL071V1 Datasheet, PDF (1/6 Pages) STMicroelectronics – Periodic self-tuning possible

STEVAL-ILL071V1
LED backlight demonstration based on the STP04CM05,
ST1S40 and STM32F030
Data brief
Features
 24 1-Watt LEDs for ~ 25 W total
 Scalable solution capable of cascading
multiple boards for larger systems (pinouts
for connection to other boards)
 Preset demo mode for adaptive voltage
control, error representation and brightness
control
 Adaptive rail voltage correction for minimal
device dissipation and higher efficiency
 All channels monitored and worst-case
corrected
 Periodic self-tuning possible
 Self-tuning at each startup corrects aging
behavior of LEDs
 Double-layered PCB
 RoHS compliant
Description
The STEVAL-ILL071V1 demonstrates how to
implement LED backlighting based on the
STP04CM05 high current LED driver, the
ST1S40 step-down DC-DC converter and the
STM32F030 ARM Cortex-M0 microcontroller.
This board features 24 LEDs (8 LED strings with
3 LEDs per string) but additional modules can be
cascaded for a larger backlight area. Possible
application may be extended to any LED lighting
system based on integrated LED drivers. The
design optimizes the LED driver rail voltage such
that dissipation within the driver is minimized. It
employs an adaptive process to compensate for
aging effects of the LEDs (forward LED voltage
increases with time). This is achieved by tracking
the drop across the LED string using the ADC of
the STM32F030, and acting accordingly on the
feedback pin of the ST1S40 (via PWM) to adjust
rail voltage until the LED driver comes out of
constant current mode. This knee point of
operation is detected and the DC-DC converter
output is locked to the minimum voltage at which
the LED driver is able to maintain constant
current operation. This ensures minimum drop
across the driver channels and thus minimum
loss within them, improving efficiency, reducing
power comsumption and increasing reliability.
March 2015
DocID027640 Rev 1
For further information contact your local STMicroelectronics sales
office
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