Data converters meet image
06 February 2008
Three octal, or eight-channel, ADCs claim to reduce power consumption by 30 per cent and increase sampling speeds, up to 65million sample/sec, for high resolution imaging.
The ADS528x ADCs from Texas Instruments (www.ti.com) address the problem of designing complex medical imaging systems into increasing smaller packages and ones which have to be portable, requiring less power consumption.
The ADS5281, ADS5282 and ADS5287 have up to 30 per cent lower power consumption than competing ADCs available yet offers a high sampling rate of 65million sample/sec while consuming just 77mW per channel. Dynamic scaling, a 30million sample/sec consumes 48mW per channel. The family is designed to interface with the company's VCA8500 octal variable gain amplifier which has 0.8nv/square root Hz noise at only 63mW per channel power consumption. Combined, these two can provide improved noise performance at less than 130mW per channel at 50million sample/sec for medical signal chains.
A low frequency noise suppression mode eliminates the 1/f flicker noise to improve SNR. Overload recovery circuitry allows each ADC to provide valid data within one clock cycle after an input overload of up to 6dB. This allows for immediate signal recovery and processing. Programmable gain is from 0dB to 12dB and full scale outputs can accommodate input signals as low as 0.5V peak to peak.
To accommodate the trend towards integrated systems and smaller medical instruments, the devices are available in a 64pin, 9mm x 9mm QFN package, as is the VCA8500. The ADS5281 has 50mllion sample/sec rate and 12bit resolution; the ADS5282 and the ADS5287 have 65million sample/sec rates, 77mW dissipation, compared to the ADS5281's 64mW, and 12bit and 10bit resolution respectively.
Evaluation modules, deserialiser and capture cards are available.
With the credentials of low power, high sampling rates, high resolution and low noise, the converters can also be used in automatic test equipment, military guidance systems, video equipment and wireless comms.
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