To control the backlight of the LCD you can input value from 0 (LCD completely closed) to 255 (maximum brightness) in: /sys/class/backlight/backlight/brightness
If you are using pico-SAM9G45 without a LCD attached the backlight booster (L11) will get very hot due to the fact that the booster has no current load.
How to disable the booster circuit:
1) To disable backlight booster circuit, you will need to input 0 to backlight control.
echo 0 > /sys/class/backlight/backlight/brightness
2) Alternatively, if your OS build does not have this kind of control capabilities, you can simply remove the L11 inductor. L11 is located near the 40pin ZIFF connector.
3) If you're using "console only" version of Angstrom OS the backlight booster is disabled automatically.