audio/videoZONE Products for the week of September 10, 2007
Avago Technologies Says…
APDS: Ambient Light Sensor with Logarithmic Output
Expanded Brightness Range Enables Sensor to Operate Under Direct Sunlight
Ideal for Outdoor Lighting, Solar Panel, Mobile Applications
Avago Technologies announced a new ambient light sensor with a precise, logarithmic output response over a wide range of lighting conditions. The company is a leading supplier of analog interface components for communications, industrial and consumer applications. The APDS-9007 is the newest addition to Avago’s ambient light sensor product family. With logarithmic output, the new sensor is designed to cover a wide range of brightness (3 lux to 70 K lux). This makes ambient light sensing suitable for mobile and other applications, such as outdoor lighting and solar panels, which may be operated under direct sunlight.
This product could, deservedly, be reviewed in green-techZONE.
When I drive out of the core of my nearest city there is an electronic LCD billboard that is, perhaps, thirty feet on the diagonal. A second display is angled at forty-five degrees to it to catch travelers from the other direction. Day and night this thing puts out the same number of lumens. You can read it in the middle of a full summer's day, and you can get blinded by it on a nice dark night. It needs a light sensor and a dimming control…
Same thing in a city like San José. All the traffic lights are LEDs. During the day the light output is fine; at night it can be blinding -- and as there is no perceptible delay in the illumination, no ramp up, it makes the effect even worse. Hopefully, in the replacement cycle that is supposed to be happening soon, someone will think green and put in a light sensor and a dimmer.
These are the sorts of applications that the APDS-9007 was designed for. This is an ambient light sensor with a logarithmic characteristic for a light range of 3 lux to 70 k-lux. The characteristic is set up by a logarithmic function in the feedback of the transimpedance amplifier that is driven from the light-sensing diode. The output is an almost perfect, straight-line, transfer characteristic.
The light spectral response very much follows that of the human eye with a little more sensitivity in the 500 nm - 510 nm range and a slightly faster fall-off in sensitivity above 650 nm.
The APDS-9007 has a shutdown pin and is also equipped with temperature compensation. It operates from a supply range of 2 V to 3.6 V with a typical quiescent of a little more than 200 µA (depends on input light level).
The output of the part can be connected directly to the ADC of a microprocessor, provided there is a resistive load external to the micro.
The package is 0.8 mm high, 2.4 mm long and 2.0 mm wide.
The APDS-9007 will be used in electronic billboards and other signs and traffic lights. It can also find applications in lap tops, mobile phones, and in TV displays. There are also huge potential power savings in automating both residential and commercial lighting. This part will do extraordinarily well.
The APDS-9007 is in production in its chipLED SM package priced at $0.45 in moderate volumes.