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National Semi ADC features serialized LVDS outputs

Posted: 14 Feb 2003 ?? ?Print Version ?Bookmark and Share

Keywords:national semiconductor? adc10s04? adc? analog digital converter? digital signal conversion?

National Semiconductor Corp. has integrated an LVDS serializer with a 10-bit, 40MSa/s ADC to create what it claims is the first ADC with serialized LVDS outputs.

Designed for ultrasound systems, copiers, and communications equipment, the device, designated the ADC10S04, allows designers more flexibility in system partitioning, said Suresh Ram, marketing manager for National's Data Conversion Systems product group.

The device also lets designers place analog and digital signal-processing blocks on separate boards and then transmit digitized data from the ADC over cables or backplanes, he said.

Ram noted that ADC outputs generate a significant amount of noise at very high speeds. "This problem has been addressed with parallel LVDS outputs that have low voltage swings, but we're improving on that solution by providing serialized LVDS outputs that further reduce noise and improve dynamic performance."

LVDS technology allows serial data transmission at thousands of megabits per second with low-voltage signal swing and current-mode driver outputs that create very low noise and provide power consumption that is almost flat across frequency. Ram added that differential data transmission, used in LVDS, is less susceptible to common-mode noise.

The ADC10S040 transforms sampled data into an LVDS serial data stream with an embedded clock. "While a conventional 10-bit ADC will have 10 pins dedicated for the digitized output signal, this device provides the digital output through two pins by serializing data at 400Mbps. Clock-to-data skew is eliminated because the clock is embedded in the data stream," Ram explained. "Also, a synchronization mode allows a deserializer to establish lock to a signal within specified lock times."

Ram added that in an ultrasound system with 128 ADC channels, National's part can eliminate 1,024 traces on a PCB, thereby lowering costs and facilitating a smaller form factor. And "in copiers, the low-output-voltage swings in serialized LVDS outputs help reduce EMI."

The ADC10S040 is sampling now in limited quantities, packaged in a 32-pin TQFP and priced at $7.50 in lots of 1,000.

EE Times

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