Ui Illumination - Nokia RX-44 Service Manual

RX-44
System Module
Figure 39 Main flex layout

UI illumination

Display backlight power supply is implemented with Betty's current regulated step-up converter. The most
important edge conditions are sufficient high output power and efficiency of the converter. Dimming of
backlights is implemented with traditional PWM control.
Qwerty keyboard and Rocker button backlights are supplied by two TPS75105 converters that are controlled
by PWM signal fed from Keyboard controller. Keypad illumination conditions are controlled by OMAP2420POP
according the device state and ambient light conditions.
Keypad controller communicates with OMAP2420POP through GEN_I2C bus. RGB LED which is placed in top
left corner of the device is used to indicate the status of the device mainly when the display has been turned
off.
The on / off control for indication LED is implemented using integrated RGB LED driver LP5521. RGB controller
communicates with OMAP2420POP through GEN_I2C bus.
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