Nokia N900 Service Manual

ALS technical description and troubleshooting
Ambient Light Sensor
Ambient Light Sensor
Figure 11 Ambient Light Sensor
Ambient Light Sensor consists of the following components:
•
Ambient Light Sensor (ALS)
ALS is a digital I2C interface component, having two channels with different spectral sensitivities. When
combined, the component responds to illuminance similar as human eye.
•
Vdd Filtering capacitor C1530
Ambient Light Sensor information is used to control keypad and display brightness of the phone.
Keyboard backlight is turned OFF when it is not needed. Display brightness is dimmed when environment
lighting is dark.
Ambient Light Sensor is calibrated in production and can be re-tuned in service points though not
recommended unless calibration coefficient are lost for some reason
ALS troubleshooting
Context
Functionality check:
Steps
1. Connect phone to Phoenix and set the phone (e.g. on the table) so that the amount of ambient light seen
by ALS is as stable as possible.
2. Start Phoenix
3. Choose File -> Scan product
4. Choose Testing -> Display Test
5. Open the Lights tab, check Ambient Light Sensor check box, click Read, cover the sensor and click Read
again. When covered, Luminance reading should be less than after clicking Read without covering the
sensor.
RX-51
BB Troubleshooting
Page 3 –44 COMPANY CONFIDENTIAL Issue 1
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Nokia N900 Specifications

General

RAM	256 MB
Internal Storage	32 GB
Operating System	Maemo 5
Battery	Removable Li-Ion 1320 mAh battery (BL-5J)
Weight	181 g
Network	GSM / HSPA
SIM	Mini-SIM
GPU	PowerVR SGX530
Memory Card slot	microSD, up to 16 GB (dedicated slot)
Loudspeaker	Yes, with stereo speakers
3.5mm jack	Yes
GPS	Yes, with A-GPS; Ovi Maps
Sensors	Accelerometer, proximity, compass
Talk time	Up to 6 h 30 min (2G) / Up to 4 h 30 min (3G)
Display	3.5 inches, 800 x 480 pixels
Processor	TI OMAP 3430
Camera	5 MP
Dimensions	110.9 x 59.8 x 18 mm
Connectivity	Wi-Fi 802.11 b/g, Bluetooth 2.1
Radio	Stereo FM radio
Browser	HTML, Adobe Flash