Direct digital synthesis on a tenth of the power

Analog Devices has a new family of direct digital synthesisers that deliver a 400MHz clock speed at one-tenth the power consumption of previous solutions.

Analog Devices has a new family of direct digital synthesisers that deliver a 400MHz clock speed at one-tenth the power consumption of previous solutions.

This now enables designers to use DDS for fast frequency hopping at higher output frequencies in more power-sensitive applications.

DDS, which is the technique of digitally creating and manipulating sinewaves - or other continuous waveforms - in the digital domain, is the preferred technology for applications requiring superior digital frequency agility, output phase control, and excellent phase noise performance.

Typical applications include satellite communications, broadband networking, radar, test and measurement, and instrumentation.

The new DDS devices are the first in the industry to clock at 400Msample/s and synthesise frequencies of up to 160MHz while dissipating less than 200mW of power.

Previous DDS chips of comparable resolution could only synthesise frequencies up to 120MHz and dissipated 2W of power.

The lower power dissipation now allows designers to use multiple chips on a single PCB with less concern for thermal issues.

Additional features of the family include an integrated 14bit D/A convertor, on-chip RAM, phase offset and amplitude control, and multichip synchronisation.

"Designers of radar systems and shaped FSK (frequency-shift keying) communications applications now have increased flexibility and the ability to enhance accuracy, tuning and phase control by using the automatic linear and nonlinear frequency sweeping capabilities of these chips", said Kevin Kattmann, Product Line Director for High-Speed Convertors, Analog Devices.

"This combination of breakthrough speed and power dissipation will extend the attributes of DDS into many new applications that were previously bound by the limitations of traditional analogue synthesis technology".

The new DDS family comprises four new 14bit devices with various added benefits.

The feature sets were selected to allow designers to purchase only the functionality needed for the desired application.

The four family members and added functionality are the following: the AD9951 Basic DDS with onboard 14bit DAC; the AD9952 with high-speed comparator; the AD9953 with RAM (allows nonlinear phase/frequency sweeping); and the AD9954 with high-speed comparator, RAM, and automatic linear frequency sweep.

As the flagship product in the new DDS family, the AD9954 features a 14bit D/A convertor operating up to 400Msample/s, as well as a high-speed comparator, RAM, and automatic linear frequency sweep.

The chip is digitally programmable and is a complete high-frequency synthesiser capable of generating a frequency-agile analogue output sinusoidal waveform at up to160MHz.

The AD9954 is designed to provide fast frequency hopping and fine-tuning resolution (32bit frequency tuning word).

The frequency tuning and control words are loaded into the AD9954 via a serial I/O port.

The AD9954 includes an integrated 1K x 32bit static RAM to support flexible frequency sweep capability in several modes.

The AD9954 also supports a user-defined linear sweep mode of operation.

The AD9954 is specified to operate over the extended industrial temperature range of -40 to +85C.

All parts are available now in 48-lead EPAD-TQFP packages with prices starting at $13.75 per unit in 1000-piece quantities.

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