Rev 1.0
TSL2550EVM
User’s Guide
An Evaluation System for the TSL2550 Ambient Light Sensor
I
NTRODUCTION
TAOS’ Ambient Light Sensor (ALS) solution can be used to automatically adjust the brightness level for
a computer display under a wide range of lighting conditions. As one of the primary benefits of using
TAOS’ ALS, battery life can be significantly increased by minimizing the power required to illuminate a
display under various ambient lighting conditions. In PC notebooks, for example, the display panel
and inverter (which delivers the power to the display panel) account for approximately 33% of the
total power consumption. TAOS’ ALS helps control the display backlight and keypad illumination in
portable equipment like notebooks, PDAs, and cell phones. There are other applications supported by
the ALS that include street light control, security lighting, digital cameras, sunlight harvesting,
automotive instrument clusters, and projection and big-screen televisions.
TAOS’ ALS can also help extend the longevity of the LCD lamp life by automatically controlling the
display brightness or luminance. Lamp life depends strongly on the lamp current and is directly
proportional to display brightness levels. Unnecessarily over-driving the display with high operating
currents and excessive brightness will prematurely degrade the lamp life of a display. Automatically
controlling the illuminance to extend lamp life is beneficial in a variety of applications:
Mobile users who frequently use notebook computers in different ambient lighting conditions
Digital monitors with on-screen controls to extend the display life and lower power consumption
Kiosks that continuously operate 24/7 in sunlight or artificial lighting
Automatically adjusting automobile display clusters (e.g. for navigation system) for safety to retain
the driver’s eyes on the road ahead at all times and eliminate glare to achieve better visibility at
night
Thirdly, since TAOS’ ALS closely approximates the response of the human eye, it can also help
improve visual performance. While eyestrain is not believed to permanently damage one’s eyes or
cause a loss of vision, it can be very uncomfortable and lead to a loss of productivity. Using TAOS’
ALS, excessive display brightness can be eliminated and productivity can be increased by maintaining
an optimal brightness level under various lighting conditions.
The TSL2550EVM helps facilitate evaluation of the TAOS Ambient Light Sensor (ALS). Two evaluation
module options are available which simply connect to a personal computer via a PCMCIA card slot or
serial communication port. Both evaluation modules include application software allowing the user to
easily control various features of the TSL2550 device. Figure 1 is a group picture of both evaluation
modules.
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