Nokia N72

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
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