Nokia RM-506 Service Manual page 226

RM-505; RM-506
System Module and User Interface
Figure 77 Backlight control for HW keys
Display backlights
Display backlights consist of two LED chains, each containing three LEDs in series powered by TPA61061
switching mode power supply. Display backlight brightness is controlled by the CABC signal, and the equality
of the current (and thus the brightness) through the two LED chains is ensured by a current mirror.
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