"Industry-First" CCD Processors Take A Bow
In a move calculated to make CCD color imaging--especially for flatbed scanner and color copier designs--even more cost-effective, linear chip maker Analog Devices, Inc. (ADI; Norwood, MA) has announced a dedicated three-channel analog signal processor chip. ADI claims its AD9814 is an industry-first.
As the latest member of ADI's expanding imaging product line, the AD9814 is billed as the first 14-bit analog front end (AFE) for scanner applications that includes all circuitry necessary to process RGB-output (red, green, and blue) CCD array signals--with low crosstalk between channels.
Highly integrated, the commercial temperature range IC includes an input clamp, a correlated double sampler (CDS), an offset DAC, and a programmable gain amplifier (PGA). All are multiplexed to the chip's 14-bit A/D converter. Thanks to ADI's advanced fabrication technology, the IC also touts low crosstalk between channels.
In terms of datasheet performance, the AD9814 guarantees no missing codes--even when operating at speeds of 10 Msamples/second on all three channels (minimum conversion speed is six Msamples/second). That should make it suitable for demanding applications such as flatbed and film scanners, digital color copiers, and multifunction peripherals. In the near future, ADI says it will spin a similar chip for less demanding applications.
It's Serially Configured
In a typical application, the AD9814's 14-bit digital output is MUXed into an eight-bit output word, which is then accessed over two read cycles.
The chip's internal registers are programmed through the device's three-wire serial interface. Among other things, the registers permit you to adjust gain, offset and operating mode. The IC's CDS amplifiers can also be disabled for use with sensors that don't require CDS, such as contact image sensors (CISs) and CMOS active pixel sensors.
In addition to that kind of flexibility and serial addressability, the AD9814 is also a high-performance linear part. For example, it offers a typical differential nonlinearity (DNL) spec of only +/-0.6 LSB, with a maximum DNL of +/- 1.0 LSB. Typical integral nonlinearity (INL) is +/-4.0 LSB.
In lockstep with today's high-density products, the chip's packaging is also very compact. Indeed, ADI says the AD9814--in a 28-pin SOIC--has the smallest footprint of any CCD-imaging AFE. Dissipation is also low. Operating from a single +5 V supply, typical power is about 400 mW, but ADI says a tad over 300 mW can be achieved. The device is also power managed, packing programmable Sleep/Power-Down modes.
In 1,000-piece quantities theses devices are priced between $8 and $20 each. For price-sensitive consumer scanner applications, ADI says it will soon release a Type AD9822, which will be pin-compatible with the '9814s, but will be lower priced.
For more information, contact Analog Devices, Inc., Ray Stata Technology Center, 804 Woburn St., Wilmington, MA 01887. Phone: (800) 262-5643, or (781) 937-1428. Fax: (781) 937-1021.