Electronic Design

Light-To-Frequency Converter Offers High Sensitivity, Low Noise

Able to sense ultra-low light levels undetectable by most silicon-based sensors, the TAOS TSL237R light-to-frequency converter with a 5,000,000:1 dynamic range combines enhanced sensitivity with low dark-signal levels.

This device senses down to 0.00002 Lux and has typical dark frequency down to 0.1 Hz. It produces a square-wave output signal with 16-bit resolution and frequency proportional to light intensity. Also, it can be interfaced directly to a DSP or a microcontroller, eliminating the need for an analog-to-digital converter.

"When you convert directly from a current to a frequency, a data converter or an amplifier are not needed. This eliminates voltage offsets and nonlinearities," says Ray King, a medical marketing specialist at TAOS.

"This is a very ubiquitous device that opens up many new applications," says Carlo Strippoli, vice president for marketing and sales. He cited automotive sensors, color calibration of computer monitors, densitomers, medical pulse oximetry, laser printers, photography, lighting control, and industrial pollution monitoring among these applications.

"Key to the product's development is that it is designed to be stable with high levels of dark current at elevated temperatures," explains Jack Berlian, director of new product development. The TSL237R operates from −25°C to 70°C. "The fact that we're using a current source also makes it inherently a wide-dynamic-range part."

The TSL237R comes in a three-pin Side Looker package. It costs $1.67 each in 1000-piece quantities.

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