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Analog front end revs multifunction peripherals

Posted: 07 Nov 2006 ?? ?Print Version ?Bookmark and Share

Keywords:National Semiconductor? LM98714? AFE? analog front end? front end?

National Semiconductor Corp. said its a new three-channel, 16bit analog front end (AFE) improves the performance of multifunction peripherals targeted at small office environments, allowing color copying speeds exceeding 40 pages per minute. Operating up to 45MHz, the LM98714 is said to be the first AFE to integrate a programmable timing generator for CCD or contact image sensors as well as serial LVDS outputs.

Today, the only option for high-speed color copying is a large and expensive office machine about the size of a filing cabinet. The new AFE enables cost-effective architectures that achieve high copying speeds in smaller, desktop-size machines. Its features allow designers place the AFE directly on the CCD board, which optimizes system partitioning and reduces EMI, while enabling high-speed copying.

The 45MSps AFE promises an SNR of -74dB and a power consumption of 505mW. These specifications also make the device suited for use in bank-note readers, high-speed document scanners, facsimile equipment, and flatbed and handheld color scanners.

Unique architecture
The fully integrated AFE promises high-speed signal throughput with a unique architecture that uses either correlated double sampling or sample-and-hold (S/H) inputs, the company said. It also has signal paths that use a 10bit offset correction DAC, 8bit programmable gain amplifiers and independently controlled digital black-level correction loops for each input. The PGA and offset DAC are programmed independently, which allows unique values of gain and offset for each of the three inputs. The signals are then routed to a 45MSps ADC.

National offers the companion DS90CR218A Channel Link receiver for applications requiring external LVDS capability. Available in a 48-pin TSSOP package, the DS90CR218A converts the three LVDS data streams back into 21bits of CMOS/TTL data for interfacing with the image processor/ASIC. With low power and LVDS signalling, the chips work together to reduce EMI from data transfer and decrease the number of wires in the cable.

In addition, the LM98714 AFE can be configured to operate in several different modes to provide maximum flexibility to designers. For compatibility with older ASICs and to simplify system debugging, the AFE also includes a CMOS output option.

The LM98714 AFE is available today in a 48-pin TSSOP package and priced at $6.60 in 1,000-unit quantities.

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