Nokia 5140 Manuales De Servicio
Nokia Customer Care
System Module and User Interface
NPL-4/5
Issue 1 05/04
Copyright © 2004 Nokia Corporation. All rights reserved.
Page 69
Figure 29: Keyboard Led Driver and Control Diagram
Display and air bubble LED driver
LEDs are supplied from VLED voltage throught current limiting circuit. Display and air
bubble illumination is controlled by DLIGHT –line (UEMEK). BJT driver controls the con-
stant current generator.
bubble illumination is controlled by DLIGHT –line (UEMEK). BJT driver controls the con-
stant current generator.
-
Driver will work as constant current generator increase or decrease the output voltage
for LEDs to keep the current stable. Serial resistance 33R is used to create the current
limit with transistor Vbe voltage.
limit with transistor Vbe voltage.
-
Air bubble led is located under the air bubble. Its current consumption will be ~3.8mA.
Figure 30: Display and Air Bubble LEDs driver and Control Diagram
Flashlight LEDs driver
LED is supplied from VLED voltage throught current limiting circuit. Flashlight is con-
trolled by CallLED2 line (UEMEK). BJT driver controls the constant current generator.
CallLED2 line needs voltage matching for higher VLED voltage than battery voltage. Cur-
rent consumption will be 20mA.
trolled by CallLED2 line (UEMEK). BJT driver controls the constant current generator.
CallLED2 line needs voltage matching for higher VLED voltage than battery voltage. Cur-
rent consumption will be 20mA.
R=39Ω
VLED
DLIGHT
UI Board
R=27Ω
VLED
DLIGHT
R=1000
Ω
Ω
Display
Air bubble
led
NA