User Guide

Keyboard

The device keyboard is connected to the main PWB with a board-to-board connector.

The keymatrix has six rows and four columns. The voice key on the main PWB and the navigation key are

connected to the same keymatrix.

Table 7 Keymatrix

Col3 Col2 Col1 Col0

Row0 Right Left Right soft key Left soft key

Row1 Down Up Send Select

Row2 8 3 2 7

Row3 6 1 5

Row4 # * 9

Row5 4 Voice End

Row6 Apps Clear Edit 0

Display and keyboard backlight

The device has one Led Driver (SMPS) that is used to drive both display and keyboard LEDs.

Both display LEDs (4pcs) and keyboard LEDs (4pcs) are connected in series.

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.

Control signals for LED driver are:

From To Voltage Function

GenOut1 TAHVO R2302 (10k) 0V / 1.8V Maximum current

control (0V ->max

curr.)

GenOut2 TAHVO R2301 (4k7) 0V / 1.8V

PWM TAHVO J2309, N2301 PWM 0%-100%,

1.8V

Current PWM

control (16 steps)

GenOut3 TAHVO 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 a lightguide (part of front

cover), phototransistor (V4400)+ resistor (R4401), NTC + resistors (R4400, R4402, R4403) and RETU EM ASIC

(N2200). Information of ambient lighting is used to control 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.

RM-1

Nokia Customer Care System Module

Page 9–20 Company Confidential Issue 1