Figure 78 Display block diagram
Backlight and illumination
This device has two backlighting systems; one for the display and one for the HW keys and other illumination
zones.
Backlighting for HW keys
The L5521 LED contoller is used for backlighting the HW keys . There are two LP5521 in the reference HW
making it possible to have up to three LED zones each.
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.
RM-555
System Module and User Interface
Issue 1
COMPANY CONFIDENTIAL
Page 6 –25
Copyright © 2009 Nokia. All rights reserved.
Содержание RM-555
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