Ambient light sensors are used as backlighting controls in any number of LCD display applications from consumer electronics to automotive, and by automatically adjusting display brightness, they can conserve battery life, which is a key benefit in mobile device applications. In addition, these sensors work well in all kinds of light sources from natural sunlight to fluorescent and incandescent lamps.
One common theme running throughout most of these recent product launches is that these ambient light sensors match or virtually match the requirements of the human eye. This is a big deal when it comes to reducing eye strain. These include sensors from AMI Semiconductor, Avago, Capella, Osram, and Vishay.
In a few instances, manufacturers have developed ambient light sensors that target both mobile device and automotive applications. For example, AMI Semiconductor's (Pocatello, Idaho) AMIS-74980x ambient light sensor may be used in both consumer and automotive applications. These devices automatically adjust display brightness based on the environment and operate equally well in a variety of light sources ranging from natural sunlight to fluorescent, conventional incandescent and halogen lamps. An important feature of the AMIS-74980x is its low dark current, enabling the display controller to adjust the brightness of the display even in low light-level environments.
Similarly, the ALS SFH5711 ambient light sensor from OSRAM (San Jose, Calif.) touts human eye characteristics for mobile devices and automotive applications. These devices are said to accurately match or imitate the sensitivity curve of the human eye, enabling mobile device displays and their brightness levels to be adjusted more precisely. The ALS SFH5711 is also suitable for automotive applications including cockpit dimming and headlight control.
Making it easier to read mobile phones, personal digital assistants (PDAs) and other mobile terminals used in cars in all lighting conditions, the "human eye" properties of the ALS SFH5711 were developed through a new material system that replaces traditional silicon, according to the company. The logarithmic amplifier integrated circuit (IC) enables a large brightness range (from 3 lx to more than 30,000 lx) to be detected with great accuracy and without the need for various series resistors for a smaller and more accurate design.
Specifically designed for mobile devices, Avago Technologies (San Jose, Calif.) offers the APDS-9004 ambient light photo sensor as a backlighting control for consumer LCD display applications for notebook PCs, DVD players, digital cameras and mobile phones.
With its automatic adjustment feature, these sensors save power and extend the life of LCD screens in these portable display product applications. In addition, they control the backlighting in these applications based on predetermined conditions set by the manufacturer.
The APDS-9004 can also be used for turning on/off indoor and outdoor lighting, street lighting and electronic signs and signals. These sensors also perform equally well in a variety of light sources ranging from natural sunlight to fluorescent, conventional incandescent, and halogen lamps.
Capella Microsystems' (Santa Clara, Calif.) Filtron family of ambient light sensors — the CM3200HS, CM3200 and CM3000 — is also said to extend battery life for mobile devices by eliminating excessive backlighting. Suitable for notebook computers, cell phones, DVD players, PDAs, MP3 players, iPods and GPS systems, these chips detect the amount of ambient light in the environment and adjust the LCD brightness accordingly to virtually match the requirements of the human eye, said the company.
Developed for advanced automotive features, the TEMT6200F, TEPT5700 and TEPT4400 ambient light sensors from Vishay Intertechnology (Malvern, Pa.) allow automatic control of LCD brightness and enable automotive driver comfort and safety features.
Vishay provides designers with a choice of surface-mount 0805, leaded 5-mm flat-top, or 3-mm packages. The angle of half intensity is ±60 degrees for the TEMT6200F, ±50 degrees for the TEPT5700 and ±30 degrees for the TEPT4400. In automotive applications, the sensors will enable automatic headlight control, tunnel sensors, and displays that adjust automatically to changes in ambient brightness. Providing a simple two-pin connection, these sensors may be used to reduce power consumption in consumer electronics applications by controlling keypad backlights and adjusting LCD brightness.
Vishay also offers a development kit for its ambient light sensors that allows development engineers to measure and display ambient illumination, tune the sensor, define their software program responses, and complete a hardware layout.
