Continuous-time architecture is first for ADC

Eight-channel 12bit 50Msample/s ADC offers an alias-free sample bandwidth up to 25MHz, while consuming 30% less power than competing pipeline devices.

National Semiconductor has announced the availability of the industry's first high-speed continuous-time sigma-delta (CTSD) A/D convertor.

The ADC12EU050, a member of National's PowerWise energy-efficient family, is an eight-channel 12bit 50Msample/s ADC that offers an alias-free sample bandwidth up to 25MHz, while consuming 30% less power (350mW) than competing pipeline devices.

This low-power breakthrough enables manufacturers to extend battery life and reduce heat in portable medical ultrasound and industrial imaging equipment.

CTSD technology has been the subject of university and industry research for more than 15 years.

With the introduction of the ADC12EU050, National is the first manufacturer to successfully transition CTSD technology from the research lab to the production line.

National plans to expand its CTSD ADC product offering for imaging, communications, and test and measurement applications that require high dynamic performance at extremely low power.

The continuous-time architecture greatly simplifies system design as it allows the integration of other signal-path functions, such as signal conditioning, while incorporating anti-aliasing filtering into the ADC.

The ADC12EU050's innovative CTSD architecture offers many advantages compared with traditional pipeline architectures, such as: lower power dissipation; an integrated lowpass, brickwall anti-aliasing filter that blocks out-of-band signals from aliasing down in-band; an easy-to-drive purely resistive input stage that does not require a sample-and-hold amplifier; and integrated phase-locked loop (PLL) and voltage-controlled oscillator (VCO) that performs clock conditioning, enabling system designers to use inexpensive clock sources; and on-chip instant-overload recovery (IOR) circuitry that recovers from saturation within one clock cycle, if the input exceeds predetermined limits.

The ADC12EU050 octal CTSD ADC offers an alias-free sample bandwidth up to 25MHz and a conversion rate of 40 to 50Msample/s.

The device features 68dB of signal-to-noise and distortion (SINAD) and a signal-to-noise ratio (SNR) of 70dB full scale.

Operating from a 1.2V supply, it consumes 44mW per channel at 50Msample/s for a total power consumption of only 350mW.

The ADC12EU050 reduces interconnection complexity by using programmable serialised outputs, which offer industry-standard low-voltage differential signalling (LVDS) and scalable low-voltage signalling (SLVS) modes.

The ADC12EU050 operates over the -40 to +85C temperature range and is supplied in a 10 x 10mm 68-pin LLP package.

Samples of the ADC12EU050 are available now, with high-volume quantities scheduled to be available in Q3 2008.

The ADC12EU050 is priced at US $64 in 1000-unit quantities.

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