Display And Keyboard Backlight - Nokia RM-313 Service Manual

RM-313
System Module

Display and keyboard backlight

The device uses SMPS Led Driver to drive display and S60 keyboard LED's. Three display backlight LED's are
connected in series (located in display module). Three S60 LEDs are also connected in series, parallel to display
LED branch via current mirror. Current feedback is done with display LED current. SMPS (N1151) and related
discrete components are located on system/ RF module. Current mirror and S60 LED's are placed on UI-FPC.
Display LED brightness can be controlled with PWM signal (0-100%, ~293Hz). S60 LEDs can be turned OFF
separately.
ITU keyboard and Side Keys are illuminated with LED's that are driven with charge pump N1150. ITU keys can
be turned on as one group. Side keys will always be turned ON and OFF as a light sequence. Brightness of
charge pump driven LED's cannot be controlled
Figure 53 ITU/S60 display circuitry
Issue 1 COMPANY CONFIDENTIAL Page 6 –25
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