Backlight issue fix?

[megous]

@bcnaz I believe the issues is twofold: how "low" the brightness can go, and PWM strobing.

PWM is only used to generate reference voltage for the stable current source. Backlight brightness is not done by PWM strobing of the backlight LEDs themselves.

Unfortunately the reference voltage for PWM GPIO pin is not completely stable. Any variation in that voltage is quite visible on the LED bightness, especially since at low brightness backlight LEDs are operating in the knee of their V-I characteristic, and are very sensitive to any change in current of the constant current source regulated by that PWM.

The further away from the knee, the less this is an issue.