A visible light sensor from Microsemi Corporation, optimized for low light levels, is said to offer “nearly perfect” human eye spectral response in applications including control of automotive displays and headlamp brightness.
The LX1973A visible light sensor uses proprietary “Best Eye” processing to provide a photopic light wavelength response curve said to nearly duplicate that of the human eye, even in dim light. Without the need for infrared or other filters, the device rejects most near-ultraviolet and near-infrared wavelengths.
Paul Bibeau, senior vice president and general manager of Microsemi's Integrated Products Group, said that when interfaced with an eight-bit A/D converter, the LX1973A can detect light as low as 0.001 lux and as high as 500 lux. An integrated dark current cancellation circuit enables accurate sensing below 0.01 lux. Internal thermal compensation provides accuracy over the –40 °C to +85 °C temperature range. Bibeau said the LX1973A's photo sensor is a PIN diode array with a linear, accurate and repeatable current transfer function. “High gain current mirrors on the chip multiply the PIN diode photo-current to a level that can be voltage scaled with a standard value external resistor,” he said. The device is lead free and, unlike some other light sensors, contains no cadmium. The sensor is available in a modified eight-pin MSOP surface-mount package that measures 3 mm square and uses only three active pins. It’s priced at $2.20 in 10,000 piece quantity.