These multichannel DDS (direct digital synthesis) devices, provide a solution to two common design challenges faced by system engineers in a range of applications. Allowing independent programming of up to four inherently synchronized outputs, ADI's new four-channel AD9959 and two-channel AD9958 deliver greater control to correct imbalances between multiple signals, enabling engineers to spend considerably less time and effort on this usually complex portion of the system design.
For space-constrained systems, the AD9958 and AD9959 simplify the design process by integrating multiple DDS channels on a single chip, eliminating the need for several single-channel DDS chips and external circuitry and offering dramatic board space reduction of up to 75 percent over traditional solutions. Direct digital synthesis is a digital technique used for generating an analog output waveform or clocking signal from a fixed-frequency clock source. The AD9959 and AD9958 are optimized for applications that require complex high speed synthesis up to 200 MHz, including phased-array radar/sonar systems, automatic test equipment, medical imaging and optical communications systems.
Used in a wide range of applications from test and measurement equipment to wireless and satellite communications, ADI's complete DDS solutions employ an on-chip high-performance DAC (digital-to-analog converter) to convert a reference frequency to a sampled sine wave
with extremely fine frequency control. DDS devices are increasingly becoming an attractive alternative to traditional frequency-agile analog synthesizer solutions as they offer considerable performance benefits, such as unparalleled matching of outputs, easier synchronization for obtaining quadrature and other signal phase relationships, and extremely fast frequency transition. Digital control eliminates the need for manual system tweaking and allows output frequencies to be conveniently derived.
In order to alleviate the design complexities typically involved in the synchronization of multiple DDS devices, the independent channels of the AD9959 and AD9958 are internally synchronized by a common reference clock. Programmable channel control allows for correction of
imbalances in external signal paths due to analog processing, such as filtering, amplification, or PCB layout mismatches. If additional channels are required, the AD9959 and AD9958 allow daisy chaining of additional DDS chips. The devices also offer extremely low power consumption of less than 165 mW per channel.
Each channel of the four-channel AD9959 and the two-channel AD9958 incorporates a high speed 10-bit DAC with excellent wideband and narrowband SFDR (spurious free dynamic range). Each fully independent programmable channel provides 14-bits of phase offset tuning, 32-bit
frequency resolution and 10-bit amplitude control. The device also supports direct or linear sweep modulation, while achieving channel isolation of greater than 60 dB. The integrated 32-bit frequency tuning word enables each channel to be programmed to resolutions of 116 mHz or less with a sampling clock of up to 500 MSPS.
Pricing and availability
The AD9959 is available in production quantities now; the AD9958 is sampling now with product quantities available in September, 2005. Both devices are specified over the extended industrial temperature range of -40 degrees C to +85 degrees C. The four-channel AD9959 and the two-channel AD9958 are respectively priced at $37.14 and $20.24 per unit in 1,000-piece quantities and are each packaged in an 8 mm x 8 mm LFCSP (lead frame chip scale package). For more information, visit www.analog.com/AD9959 or www.analog.com/AD9958.