STEVAL-ILL071V1 STMicroelectronics

S T E VA L - I L L 0 7 1 V 1 LED backlight demonstration based on the STP04CM05, ST1S40 and STM32F030 Data brief 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 Features feedback pin of the ST1S40 (via PWM) to adjust 24 1-Watt LEDs for ~ 25 W total rail voltage until the LED driver comes out of Scalable solution capable of cascading constant current mode. This knee point of multiple boards for larger systems (pinouts operation is detected and the DC-DC converter for connection to other boards) output is locked to the minimum voltage at which Preset demo mode for adaptive voltage the LED driver is able to maintain constant control, error representation and brightness current operation. This ensures minimum drop control across the driver channels and thus minimum Adaptive rail voltage correction for minimal loss within them, improving efficiency, reducing device dissipation and higher efficiency power comsumption and increasing reliability. March 2015 DocID027640 Rev 1 1/6 www.st.com For further information contact your local STMicroelectronics sales office Schematic diagrams STEVAL-ILL071V1 1 Schematic diagrams Figure 1: STEVAL-ILL071V1 circuit schematic (1 of 6) Figure 2: STEVAL-ILL071V1 circuit schematic (2 of 6) 2/6 DocID027640 Rev 1