16-bit, 10M-sample/sec ADC uses SAR architecture
By Paul Rako, Technical Editor -- EDN, July 24, 2008
Analog Devices’ new AD7626 ADC provides 16-bit samples at a 10-MHz rate while using 130 mW. The part targets use in digital-X-ray machines, MRI (magnetic-resonance-imaging) systems, and ATE (automatic-test equipment), as well as general data-acquisition, sonar, and other applications. The differential-input device uses digital-LVDS (low-voltage-differential-signaling) outputs and has an internal 4.096V buffered reference, or you can provide an external reference. A common-mode pin can supply half the reference voltage to input amplifiers. The device requires both 2.5 and 5V power supplies.
The AD7626 has good dc performance, with a typical INL (integral nonlinearity) of ±1 bit, as well as no missing codes over its output range. Typical DNL (differential nonlinearity) is ±0.3 bits. The device also offers good ac specs with a 92-dB SNR (signal-to-noise ratio) and an ENOB (effective number of bits) of 15. The part employs a SAR (successive-approximation-register) architecture, so that, unlike a pipelined ADC, each clock cycle immediately produces a valid output. Pipelined converters must clock four to six times for the correct conversion data to work its way through the pipeline and appear at the output. This limitation makes pipelined converters less appropriate in multiplexed-system applications, in which the clock-cycle latency creates more software overhead to ensure that the data is valid for a given channel.
The AD7626 is available in a 5×5-mm, 32-pin LFCSP with a suggested retail price of $34 (1000). It operates over a −40 to +85°C temperature range. Production quantities and evaluation modules are available now.
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The AD7626 demo video can be viewed on You Tube at www.youtube.com/watch?v=z6CwRxe1Jn8.
Patrick Kusior - 2008-1-8 12:05:00 PDT
