User Guide

ALS interface

Ambient Light Sensor (ALS) is located in the upper part of the phone. The system consists of the following

components:

• lightguide (part of the front cover)

• phototransistor (V4410) + resistor (R4415)

• NTC + resistors (R4414, R4416, R4417)

• 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.

Figure 72 ALS HW implementation

Table 12 ALS resistor values

Symbol R1 R2 R3 R4 R5 R6 R7 NTC-res

Value 5 kOhm 15 kOhm 30 kOhm 50 kOhm

470

kOhm

100

kohm

470

kohm 47 kOhm

RM-49

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