National Semiconductor shrinks scanner to single chip
Squeezing all of the electronics for a complete color image and document scanner onto a single silicon integrated circuit (IC) smaller than a thumbnail, National Semiconductor (NS; Santa Clara, CA; www.national.com) has accomplished what industry analysts claim is the technology needed to achieve a mass-market breakthrough in machine-vision and imaging--a system on a chip. This scanner chip is expected to permit manufacturers to build high-performance flatbed scanners at significantly lower cost. It incorporates such key functions as an analog front end, sensor clock generation, microstepping motor control, data buffering, and a parallel port interface.
Says Bill Stacy, NS vice president of the system products group, "This new chip, the LM9830, or Merlin, uses our analog technology expertise to achieve highly integrated systems on a single piece of silicon. In addition to performance and cost benefits, this advanced level of integration also shortens the time it takes our customers to get their new products to market by minimizing their electronics and software design requirements."
Adds Fred Hamilton, principal applications engineer at the NS systems products group, "Our final architecture is radically different from existing scanners, and we have seven patents either pending or being processed. Our customers can now concentrate their design resources on optimizing other parameters of their products, such as stepper motor torque and speed, scanner footprint, and software features, that will allow them to take their final product even further."
The LM9830 chip contains a 6-MHz, 12-bit analog-to-digital converter in a pipelined architecture, operates at a 6 million-pixel-per-second conversion rate, and scans images in a 36-bit color format. On-chip functions include digital offset and shading correction, gain offset, correlated double sampling, digital pixel processing, and individual red-green-blue gamma tables. These capabilities enable the chip to provide a range of horizontal and vertical resolutions from 50 to 600 dots per inch.
According to Hamilton, "We had complete freedom to put whatever we wanted inside the chip. So rather than concentrating on how scanners are designed today, we took a step back and pursued the optimum architecture for a line-based scanner." The results are tighter control over system clock rates and matching the scanner clock rate to the parallel-port-interface speed. These features enable scan speeds of two to 16 times faster than existing low-to-mid-range scanners. Moreover, by zooming in on a subset of CCD pixels, the scanner can transmit an arbitrary range of pixels to speed up the scanning of small-sized items, such as business cards. In addition, pixel depths of 1, 2, or 4 bits can be packed into bytes for faster scans of line art and low-pixel depth images.
Powered by a single 5-V source, the LM9830 chip dissipates 350 mW (typical), provides TWAIN driver software and support, comes in a 100-lead, thin quad flat pack and costs $10 in 1000-unit quantities.
