Exar introduced the industry's first 16-bit Charge Coupled Device (CCD) linear processor for imaging systems. The XRD9816 (16-bit) three-channel and XRD9814 (14-bit), combine essential analog front end and analog-to-digital functions onto a single chip.

Ushering in a new generation of fully differential, high-resolution (42 and 48-bit) digital document, and film scanners and Multifunction Peripherals (MFP) which combines scanner, copier and fax capabilities, the XRD9816 and XRD9814 products will run at 6 MSPS conversion rates, in 48-pin TQFP packages. Both devices are sampling now.

Leapfrogging the industry's current 12-bit (36-bit color) AFEs, the new XRD9816 and XRD9814 family opens the door to 48-bit and 42-bit digital document and film scanners, respectively, giving unprecedented depth and image quality.

According to John Sramek, vice president and general manager of EXAR's Video and Imaging Division, "At 16-bit and 6 MSPS, the low-noise XRD9816 pushes the limits of AFEs for scanners to a new peak. Integrating the analog functions into a single chip helps reduce the footprint and price of high-performance systems. In addition to the low-cost 14-bit device, the XRD9814, Exar also offers several 12-bit, three channel products (XRD9812 & XRD9827). Exar is a single-source for a complete range of AFEs for the digital document and film scanner market."

Technical Highlights

The XRD9816 and the XRD9814 have several important technical characteristics that distinguish them in the marketplace.

For example, the inputs of the three RGB channels are fully differential to reduce common mode noise which is a major issue in 14-bit and higher resolution in scanners. And, the XRD9814 and XRD9816 can be programmed to work with either CCD or CIS sensors. This gives scanner and copier OEMs greater design options to meet rapidly changing market needs.

In addition to increasing the resolution of the Analog-to-Digital Converter (ADC) to 14-bits and 16-bits, the three 10-bit Programmable Gain Amplifier (PGAs) can be programmed in steps of .0088 V/V. The individual offset adjustment for each color channel: Red, Green and Blue (RGB) is 8-bits, allowing off-set adjustments with a 0.25 mV step. These features allow the designer to have tighter control over these global gain and offset settings than has previously been available.

When I was still a young squirt the really cool thing to own was a "trannie", a portable superhet receiver using the first series of transistors. The component count for a superhet with a push-pull output stage was six transistors. Then, wow, a Soviet receiver came on the market -- the Volga 8-transistor radio. Had to be better, right? Actually the additional two transistors were there but all six leads were soldered to the ground plane of the circuit board (and they were probably factory duds as well.) But the marketers did not lie -- there were eight transistors. I feel kind of the same way about these Exar products. They truly are 14- and 16-bit AFEs for CCD/CIS scanners, and that is a major achievement in itself; but the purpose of those bits has little to do with engineering direction.

When you look at the performance of the best CCDs you may be looking at signal-to-noise ratios of 63-64 dB (say, 11 bits) and even with differential inputs the practical noise floor is likely to be a couple of dB worse. 16 bits of resolution is simple overkill for this kind of circuit use. Additionally, of course, what is required to be fed to a PC is an 8-bit signal that can be handled by standard picture manipulation/paint software applications. There is some engineering justification for 10- and 11-bit circuits to gain better control, to maximize performance, but the offering of 16-bit parts is a gift horse to the scanner manufacturers who will now be able to state on the cartons of their products that they handle "48-bit color." This hype is not Exar's fault and they will be on the receiving end of a goodly amount of business because of it, and that's what they are in business for. But as engineers let us not try to fool ourselves, as this press release tries to do.