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Transparent-Packaged Chip Senses Color

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TAOS, Inc. Announces Industry's First Integrated RGB Color Sensor with Digital-Compatible Interface New device's light-to-frequency converter platform enables high-resolution measurements without the need for expensive A/D converters. Plano, Texas--Designers can now take a "drop-in" approach in adding color-sensing capabilities to their new products with the industry's first integrated RGB color sensor with a digital-compatible interface announced by Texas Advanced Optoelectronic Solutions, Inc. This color sensor integrates red, green, and blue (RGB) filters on a single die. It is built on a high-performance light-to-frequency converter platform that enables 10–12 bits or better resolution per color channel without the need for expensive A/Dl converters. The TCS230 Programmable Color Light-to-Frequency Converter is well-suited for use in colorimeter measurement applications such as color printers, medical diagnostics, computer color-monitor calibration, process controls, and color-matching applications with paints, textiles, cosmetics, and printed materials. "At TAOS, our goal is to make it as easy as possible for designers to add light-sensing capabilities to their repertoire in new product designs, thereby enabling these new products to be more competitive in their target markets," said Carlo Strippoli, TAOS vice president of marketing and sales. "The TCS230 further expands the dimensions of Lumenology—the TAOS light-sensing technology—because, by allowing the designer literally to 'drop in' a full RGB range of color-sensing capabilities, it also helps reduce system costs." The TCS230 achieves its full RGB color sensing through a 64-photodiode grid that consists of four types of photodiodes: red, green, blue, and a clear for overall intensity information. The four types (colors) of photodiodes are interdigitated to minimize the effects of the nonuniformity of incident irradiance. All 16 photodiodes of the same color are connected in parallel, and the color selected for use by the TCS230 during operation is dynamically selectable via two programming pins. The device is capable of responding to light over a 250,000-to-1 dynamic range, with a typical output frequency range of 2 Hz to 500 kHz. In addition, with two other programming pins, the user may select output scaling factors of 100 percent, 20 percent, or 2 percent, or a powerdown mode. The TCS230 also provides assembly benefits because its single die configuration helps simplify mounting and optics. Much more accurate measurement is ensured because all three color filters are on the same optical plane. The TCS230 Programmable Color Light-to-Frequency Converter is available now from TAOS, Inc. and its authorized distributors. Packaged in an 8-pin SOIC surface-mount package, the TCS230D has a suggested resale price of $2.67 in 1,000-piece quantities. A TCS230 Evaluation Module also will be available from TAOS, Inc. and its authorized distributors.

In January of this year we reviewed Texas Advanced Optoelectronic Solutions' (TAOS) Type TSL2550 sensor, an SMBus-equipped chip that could accurately measure ambient light. Since then, the company has rolled out its Type TCS230 RGB converter. Somewhat like its predecessor, the power-managed TCS230 color light-to-frequency converter comes in a surface-mount package, and carries an industrial temperature-range rating. It combines configurable silicon photodiodes and a current-to-frequency converter—all on one CMOS die. In operation, the sensor's light-to-frequency converter reads an 8 × 8 array of on-chip photodiodes. Sixteen of these diodes have blue filters, 16 have green, 16 have red, and 16 are clear. All 16 photodiodes of the same color are connected in parallel. In use, the four colors are interdigitated to minimize the effects of the nonuniformity of incident light. Pin-Selectable Diodes Which type of photodiode the device uses during an application is also pin-selectable. In any case, on the sensor's output you get a 50 percent duty-cycle square wave whose frequency is directly proportional to the light intensity. The relative frequency values of the sensor's divided outputs are 100 percent, 20 percent, and 2 percent, as stated in TAOS's press release. With division of the output frequency accomplished by counting internal pulses, the final output period represents an average of the multiple periods of the principle frequency. The sensor's output frequency can also be rapidly scaled by one of three preset values via logic-level control pins. Fast scaling is a significant attribute of this device. It's accomplished by internally connecting the pulse-train output of the converter to a series of frequency dividers. Rapid Scaling The fact that you can do a fast frequency scaling is a nifty feature. It permits the device's output range to be optimized for different measurement techniques. For example, scaled-down outputs can be used where only a slower frequency counter is available, or where an inexpensive slow microcontroller is used, or where period-measurement techniques are taken rather than frequency. The sensor's CMOS/TTL-compatible I/O also mean that you can interface this device directly to your controller or external logic. The device's Output Enable (OE) pin can also place the sensor's output in a high-impedance state (three-state) so that you can share a microcontroller's input line. Here's an example schematic of the TCS230 with the sensor module circuitry as implemented on the upcoming evaluation board. click for full-size schematic When I spoke with TAOS director of new product development Jack Berline, he indicated that the evaluation board that's mentioned in the press release was slightly delayed, as the company wants to put some finishing touches on it. Slated to sell for about $150, the eval board will be equipped with a lens that will establish a field of view and depth of field for the sensor. The board will also include white LEDs as a light source. Berline says the eval board will be bundled with a Board of Education BASIC Stamp board from Parallax, Inc. Note that TAOS has a working technology partnership with Parallax. "Several TAOS parts were good candidates to work with Parallax products," explains Berline. "When used with a BASIC Stamp, the TCS230's output frequency can be read using a Stamp's BASIC Count statement, for example." Berline explains that the Parallax prototyping board will plug into a Parallax processor board, and thence into a PC's serial port. Host software will be provided to decipher the TCS230 sensor's RGB output, and then display the sensed color on a PC's screen. Most of the TCS230 chip's data and control lines will be accessible directly via BASIC Stamp port pins through a supplied AppMod adapter board. An exception is the sensor's active-low Output Enable line, which is decoded separately. This system will be able to detect and measure a nearly limitless range of visible colors. "Applications include color edge-following robots, sorting by color, and color matching, to name just a few," says Berline. Sound exciting? For more details, contact Berline at TAOS, Inc. 800 N. Jupiter Rd. Suite 205 Plano, TX 75074 Phone: (972) 673-0759 FAX: (972) 943-0610

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