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ADC promises 'extremely' accurate data measurement

Posted: 26 Jul 2007 ?? ?Print Version ?Bookmark and Share

Keywords:Delta sigma ADCs? SAR converter? analog converters? MCUs?

Cirrus Logic has released CS556x/7x/8x family of 16- and 24bit ADCs, a new family of high-precision converters that combines the higher-bandwidth, low-distortion performance features of a SAR converter with high-resolution, low-noise performance of Delta sigma ADCs. The combination of features provides designers precision instrumentation, such as industrial process controllers, laboratory instrumentation, medical instrumentation and high-speed weighing systems, with a higher level of measurement accuracy, lower noise and higher throughput.

"This breakthrough performance means that various industrial applications will be able to obtain an extremely accurate measurement of data," said John Paulos, vice president and general manager, industrial products division, Cirrus Logic. "Greater measurement accuracy leads to a wealth of benefits for industrial systems such as systems for achieving tighter production yields, higher-precision machine tools, improved temperature control, valve control and speed of flow, just to name a few."

The CS556x family overcomes critical performance issues associated with SAR and Delta sigma converters. SAR converters are typically very sensitive to noise from the converter itself or the system that the SAR converter operates. Virtually, any noise present canand often willpropagate directly to the output of the converter. The CS556x family provides a higher level of noise suppression than SAR converters, resulting in higher accuracy conversions and reduced post-conversion processing while adding to the robustness of the system.

The CS556x also offers exceptional differential non-linearity (DNL) error, which measures the accuracy of the ADC and is vital in control applications. The family features DNL error as low as 0.04 LSB typical (CS5571), compared to 1 LSB typical within SAR converters. In addition, the single-clock latency digital filter allows conversion-rate switching of the input with no loss in throughput.

The CS556x's high-throughput precision performance stands out among high-resolution Delta Sigma converters. With near-flat digital FIR filter characteristics, the CS556x product line achieves unrestricted, wide-bandwidth signal throughput usually seen only in higher-speed SAR convertersat resolutions up to 24bits. With this flat filter, output data is a 1:1 representation of the input signal across the entire frequency range, up to the sampling rate of the converter. Meanwhile, most Delta Sigma converters utilize Sinc filters, which attenuate the signal at specific frequencies.

Other additional key features of the CS556x include high-impedance buffered inputs that simplify external circuitry, fully differential inputs that provide the best possible noise rejection and dynamic accuracy, with the ability to measure bipolar signals and self calibration to ensure superior measurement accuracy over variations in supply and temperature.

A flexible serial interface eases connections to MCUs without external components (includes slave and self-sequencing master modes).

CS5560 offers 24bit resolution, a conversion rate of 50KSPS and is priced at $8.95 in 1,000-unit quantities. CS5571 offers 16bit resolution, a conversion rate of 100KSPS and is priced at $10.29 in quantities of 1,000. CS5581 offer 16bit resolution, a conversion rate of 200KSPS and is priced at $8.45 in quantities of 1,000. The CS5561/70/80 will be available in September. The ICs, which are currently in volume production, are housed in a 24-lead SSOP package.

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