Display And Keyboard Backlight; Als Interface - Nokia RM-42 Service Manual

Nokia Customer Care
Signal name
Joystick_Left
Joystick_Up
Joystick_Push
VLEDOUT2
SETCURR2

Display and keyboard backlight

The device has one Led Driver (SMPS) that is used to drive both displays and keyboard LEDs. LEDs on display
modules and on keyboard are connected so that there are 4 LEDs on K2 (in series), 3 LEDs on Jordan (in series)
and 4 LEDs on keyboard (in series). These circuits are connected parallel to Led Driver output.
Current adjustment of the driver is done from the display LED branch, and keyboard current also depends on
the display brightness.
In a typical use case, keyboard LEDs are turned ON only in dark ambient lighting conditions.
K2 and Jordan backlights can´t be turned on at the same time.
Control signals for LED driver are:
GenOut1
GenOut2
PWM
GenOut3
GenIO46

ALS interface

Ambient Light Sensor (ALS) is located in the fold part of the phone. It consists of a lightguide (part of front cover),
components of 1LB PWB: phototransistor (V1000)+ resistor (R1006), NTC + resistors (R1004, R1005, R1007) and
RETU EM ASIC (N2200)on 1HU PWB (Gromit engine). Information of ambient lighting is used to control the
backlights of the phone:
• Keypad lighting is switched on only when environment is dark / dim
• Display backlights are dimmed, when environment is dark / dim
Ambient light sensor itself is a photo transistor which is temperature-compensated by an external NTC resistor.
Retu with its ADC reads the light sensor (LS) and temperature (LST) results.
ALS calibration is not possible in the service points. It is replaced by using selected phototransistors as spare
parts.
Page 9–24
X4401 Pin #
19
15
17
1
2
From
TAHVO
TAHVO
TAHVO
TAHVO
Rap3G
Company Confidential
Copyright ©2005 Nokia. All Rights Reserved.
To
R2302 (10k)
R2301 (4k7)
J2309, N2301
V2300
-->
X4400 Pin #
Voltage
0V / 1.8V
0V / 1.8V
PWM 0%-100%,
1.8V
0V / 1.8V
BLS
RM-42
System Module
Function
Maximum current
control (0V ->max
curr.)
Current PWM
control (16 steps)
Keyboard LEDs ON
(1.8V) /OFF (0V)
Display backlight
select (1 = K2
backlights on, 0 =
Jordan backlights
on)
9241872 (Issue 1)