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Analog Devices Introduces Digital Imaging Converters Optimized for Professional Applications

12-bit CMOS and CCD analog front-end solutions improve image quality for scientific and industrial imaging applications

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Analog Devices, a provider of high-performance semiconductors for signal processing applications, announced the expansion of its industry-leading data converter portfolio with the addition of two state-of-the-art analog front-end (AFE) converters for digital imaging. Analog Devices' industry-standard AFEs are employed in a wide variety of well-known, high-performance digital still cameras and camcorders. Leveraging this expertise in consumer digital still camera technology, Analog Devices now offers devices for CMOS and CCD imaging sensors used in high-end digital still cameras and camcorders and in high-performance scientific and industrial imaging applications, such as machine vision, biomedical imaging, and crash-test analysis. "Our expertise in technology for the consumer digital still camera market has made the entry into professional imaging market a natural next step," said Willard Bucklen, product line director, High Speed Converters, Analog Devices. "Our solutions now offer industrial and scientific imaging designers the best noise performance in the industry along with the high levels of integration necessary to acquire, condition, and digitize high-resolution images." First 12-Bit, 40-MSPS AFE for CMOS Imagers The AD9821 is the industry's first 12-bit, 40-MSPS AFE. The device is designed to interface with CMOS imagers used in applications for which image quality is essential, such as medical imaging, microscopy, industrial/machine vision, digital photography, biometrics, and automatic inspection equipment. An alternative to component-based solutions using several ICs performing discrete functions, the AD9821 provides all the functionality needed to digitize an image from a CMOS image sensor on a single, integrated chip. The AD9821 features a 12-bit, 40-MSPS ADC that interfaces with high-speed CMOS sensors via a differential sensor input. It includes a low-noise optical black clamp and a 0-to-36 dB, 10-bit programmable gain amplifier. The AD9821 dissipates only 150 mW, enabling longer battery life in portable applications. The AD9845B is the industry's highest performance 12-bit, 30-MSPS AFE and is designed for high-speed, high-resolution CCD (charge-coupled devices) imaging applications, such as scientific and industrial imaging devices, as well as digital still cameras and camcorders. Addressing designer demand for higher resolution images produced at faster bit rates, the AD9845B improves upon the standard AFE resolution of 10 bits, delivering image quality 4 times higher and 1.5 times faster than any standard AFE on the market. In addition, the AD9845B features an integrated 6-bit resolution PxGA(R) (pixel gain amplifier) that enables better image quality, by allowing gain to be finely tuned to fit the image. The AD9845B includes a 12-bit 30-MSPS ADC (analog-to-digital converter), a 30-MSPS CDS (correlated double sampler), a 4 dB plus/minus 6 dB 6-bit PxGA(R), and a 2 dB to 36 dB 10-bit VGA (variable gain amplifier). It also provides an input clamp, black level clamp, and input modes for processing analog video signals. Its internal registers are programmed through a 3-wire serial digital interface. Programmable features include gain adjustment, black level adjustment, input confirmation and power-down modes. The AD9845B operates from a single 3 V power supply and typically dissipates 153 mW. Analog Devices, Inc., Ray Stata Technology Center, 804 Woburn Street, Wilmington, MA 01887. Tel: 800-ANALOGD (262-5643). Analog Devices Web Site

Technical limitations in imagers and components have been the main reason that the growth of digital imaging has been slow for industrial applications. However, the growth of the consumer market for high-end imaging products has made it a natural next step to offer similar high-end products to industrial imaging applications. The industrial and scientific imaging applications require different technical specifications than the consumer market, including more resolution and very different gain curves. However, driven by the growing digital still camera market, CCD and CMOS sensors have rapidly increased in resolution and also dropped in price, making high-performance digital imaging more accessible to these industrial markets. Analog Devices has developed two CCD signal processors that address the high-performance market segment for both types of sensors. The AD9845B is a 12-bit, 30 MSPS CCD signal processor and the AD9821 is a 12-bit, 40 MSPS signal processor for CMOS sensors. Both products are geared to the scientific and industrial market. The AD9845B includes all the components for CCD processing, acquisition, and conditioning of the signal. It includes a correlated double sampler and a pixel gain amplifier (PxGA). The PxGA is used because many CCDs are more sensitive to some signals than to others. The integrated amplifier allows you to control the amount of gain for different colors. If you didnęt have the PxGA you would get more dynamic range from some colors than others and the image would be uneven. In other words, it equalizes the dynamic range and that is important for applications such as machine vision. The amplifier gets its information about how much to control the image from the four user defined register settings of RGB and black. The user controls the settings with the gain registers that are controlled by resistors. Additionally, having the PxGA on chip is advantageous because changing gain does not affect the black-level reference. Another aspect thatęs important for high end imagers is high resolution with no missing code. These 12-bit converters improved on the typical 10-bit resolution- converters and did it with no missing code. No missing code may seem trivial but it is especially important when the image is very dark. The human eye is more sensitive to the darker shades of the image rather than whiter shades. If you have a converter that has a resolution with missing code (for example, a 12-bit converter with 1 bit missing code) then there will be missing information in the image. There will no longer be a continuous wrap from black to white and it will show a step function rather than a gradual change. The 12-bit resolution offers more resolution in the darker regions and more gradations for shades of gray. Thus, after you get the raw data you can shape the result to have more resolution in the grayer and darker areas. This becomes important for automated inspection applications. The other product is the AD9821, which is a 12-bit 40 MSPS analog front end. This addresses the low-end of the market including PC cameras. For example, it could be used for toys like a recently introduced product that uses a CMOS imager camera in one of its life-like toys. The AD9821 uses a differential input to eliminate as much noise and power dissipation as possible from the imaging application because noise affects the overall imager performance. Additionally, these high-performance CMOS imagers require the signal processor to be separate from the sensor to attain the high quality imaging. The essential difference between the AD9821 and AD9845B is that the AD9821 does not have a correlated double sampler. It uses a differential signal input that goes to a sample and hold circuit. The AD9821 replaces about 20 components, including sample and hold circuits, variable gain circuits, analog-to-digital converters, clamps, and resistors. This part does a good job of integration, and offers all the benefits of integration, such as reduced power consumption and smaller size. Thereęs little doubt that these high-end imaging products from Analog Devices will be welcomed by the scientific and industrial markets because they meet the performance needs that werenęt met by previous integrated imaging products. The AD9821 comes in a tiny (7 mm x 7 mm) 48-LQFP package and is priced at $13.02 per unit in 100-piece quantities. Samples are available now. The AD9845B is available in a compact, 48-pin LQFP package and is fully pin-compatible with all products in ADI's AD984x family of AFE products for the CCD imaging market. It is priced at $11.71 per unit in 100-piece quantities. Samples are available now. AD9821 Data Sheet AD9845B Data Sheet

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