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Three New Light-to-Voltage Converters Offer Design Flexibility for Cost Sensitive Light Sensing Applications

June 7, 2004 — Designers can now realize the benefits of an integrated optoelectronic solution — lower noise, increased reliability, reduced board space, reduced design complexity and cycle time and reduced inventory — at the price points for a discrete solution. This is made possible with the introduction of three new light-to-voltage converters from Texas Advanced Optoelectronic Solutions (TAOS). These latest TAOS light sensing solutions are well suited for the diverse applications in which a photodiode and transimpedance amplifier pair are typically used. They can perform effectively in both portable and non-portable applications such as lighting controls and electronic dimming ballasts, contrast and brightness controls in signs, media detection in printers and medical applications such as low-cost reagent strip readers.

Like other TAOS light-to-voltage converters, the TSL12, TSL13 and TSL14 Light-to-Voltage Converters provide an analog output voltage proportional to light intensity. They also have been designed to cost-effectively optimize the performance tradeoffs between sensitivity, noise and speed.

A typical discrete optoelectronic solution usually consists of a photodiode, a transimpedance amplifier and gain setting resistors. The TSL12, TSL13 and TSL14 Light-to-Voltage Converters integrate all these components on a single die minimizing noise and saving board space. Each of the three light-to-voltage converters is designed to meet the low, middle and high range responsivity and rise time performance parameters depending upon whether high sensitivity or high speed is more important for the application. The three devices are designed to provide a different tradeoff between responsivity (sensitivity to light) and rise time (speed) as outlined below:

Responsivity Rise Time
[mV per (microwatts per cm2 )] microseconds
TSL12 248 20
TSL13 64 8
TSL14 16 3

The devices operate in the 3-volt to 5-volt range and have a spectral sensitivity range of 350 nanometers to 1050 nanometers. The devices require a low supply current of 1.1 milliamp typical and will operate over a temperature range of minus 25 degrees C to 85 degrees C.

The TSL12, TSL13 and TSL14 Light-to-Voltage Converters are available now from TAOS, Inc. and its authorized distributors in a 3-pin Side Looker (S) package. In 1,000-piece quantities, the TSL12, TSL13 and TSL14 Light-to-Voltage Converters have a suggested resale price of $0.59. The TSL12 and the TSL13 also will be released in a 4-pin TMB (T) surface mount package in the third quarter of 2004.

The datasheet for the TSL12, 13, and 14 can be found
here.

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