Table 18 LED driver control signals
From
To
Voltage
Function
GenOut1
EM ASIC (N2300)
R2302 (10k)
0V / 1.8V
Maximum current
control (0V ->max
curr.)
GenOut2
EM ASIC (N2300)
R2301 (4k7)
0V / 1.8V
PWM
EM ASIC (N2300)
J2309, N2301
PWM 0%-100%,
1.8V
Current PWM
control (16 steps)
GenOut3
EM ASIC (N2300)
V2300
0V / 1.8V
Keyboard LEDs ON
(1.8V) /OFF (0V)
ALS interface
Ambient Light Sensor (ALS) is located in the upper part of the phone. It consists of the following components:
• lightguide (part of the front cover)
• phototransistor (V4400) + resistor (R4401)
• NTC + resistors (R4400, R4402, R4403)
• EM ASIC (N2200)
Information on ambient lighting is used to control the backlights of the phone:
• Keypad lighting is switched on only when the environment is dark / dim
• Display backlights are dimmed, when the environment is dark / dim
The ambient light sensor itself is a photo transistor, which is temperature-compensated by an external NTC
resistor. N2200 reads the light sensor (LS) and temperature (LST) results.
ALS calibration is not possible in the service points. ALS is serviced by replacing faulty phototransistors.
RM-180
System Module
Nokia Customer Care
Issue 1
COMPANY CONFIDENTIAL
Page 9 –25
Copyright © 2006 Nokia. All rights reserved.
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