Continuous-time sigma-delta ADCs

4 February 2009 Analogue, Mixed Signal, LSI

Analog Devices recently unveiled its continuous-time sigma-delta (CTSD) converter architecture for wireless infrastructure, medical and other high-performance equipment demanding enhanced data resolution and wide bandwidth. The 16-bit AD9261 and AD9262 CTSD converters, and the AD9267 CTSD modulator couple low noise and high dynamic range with a bandwidth of up to 10 MHz.

The highly integrated CTSD architecture eliminates multiple discrete components at the system level, while simultaneously improving performance and simplifying product development.

The AD926x utilises principles of over-sampling, noise shaping and input characteristics unique to its architecture to achieve high levels of performance and ease of use. The quiet resistive input structure relaxes the requirements of the driver amplifier, while the high-order over-sampled continuous time loop filter attenuates out-of-band signals, reducing the need for large baseband filters and other signal conditioning circuitry. The high dynamic range performance reduces or eliminates the need for automatic gain control in many applications.

The 16-bit single and dual AD926x ADC family features 86 dB dynamic range for an input signal bandwidth of up to 10 MHz. The highly integrated AD9261 and AD9262 feature an on-chip PLL clock multiplier, decimation filters, and sample rate converters and provide flexible output data rates between 30 MSps (mega-samples-per-second) and 160 MSps.

The AD9267, which features only the high-performance 640 MSps modulator core and PLL clock multiplier, presents the high speed data directly to the output. This provides designers the flexibility to offload signal processing functions to an FPGA or other processor. The 150 mW per channel to 350 mW per channel power consumption of the new CTSD converters is matched to a range of communications and industrial applications, including emerging radio architectures, such as direct down-conversion, where the dual AD9262 or AD9267 can be used to support multiple wireless carriers and standards simultaneously.

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