Manhasset, N.Y. After launching 17 high-speed converters in 2004, Analog Devices Inc. will kick off the new year with two of its highest-performing devices to date. The first is a 14-bit, 80-Msample/s analog-to-digital converter with a 5- to 7-dB improvement in spurious-free dynamic range (SFDR); the second is a 16-bit, 1-Gsample/s digital-to-analog converter with power consumption of 1 watt. Both target such applications as wireless infrastructure, broadband wireless and communications test equipment.
Aside from low power and high ac performance in terms of SFDR and intermodulation distortion, both converters were designed with high integration in mind, said John Hall, marketing manager for the high-performance A/D line at Analog Devices (Norwood, Mass.). "All converter processing is done on-chip," he said, "and an SPI interface has been provided for control and test."
In the case of the monolithic AD9444 pipeline A/D, high integration translates to on-chip decimation filters and track-and-hold circuitry, with no external reference or driver components needed. However, it's the SFDR figure of 97 dBc and the signal-to-noise ratio of 73.1 dB, both at 70-MHz input, that has Hall particularly excited.
"A high SFDR is a very important spec for our target market and this is a 5- to 7-dB improvement over currently available A/Ds," Hall said. A high SFDR allows better signal capture of weaker signals in a dynamically changing channel with interferers. That translates to more basestation design margin and fewer dropped calls, he said.
Hall said the improvement in SFDR was accomplished not by any fundamental breakthrough in A/D architectures but through good design techniques and layout. That involved good matching of components to avoid spurs, carefully designed trimming algorithms, location and isolation.
Manufactured in a 0.35-micron process, the AD9444 features LVDS- or CMOS-compatible data outputs, 3.3- or 5-volt operation, and power consumption of 1.2 W.
For the dual 16-bit AD9779 D/A, the emphasis was clearly on higher sampling rates, of up to 1 Gsample/s. This not only allows multicarrier generation for third-generation UMTS networks but also enables direct IF synthesis and more flexible frequency planning, the company said.
"The high output frequency [up to 2 GHz] allows removal of one upconversion stage," said David Carr, marketing applications manager for ADI's high-speed D/A line. "Fewer stages equals fewer things to keep track of," he said, as well as fewer components in the overall design.
The converter comes with digital interpolation filters that, among other things, simplify interfacing to an FPGA or media-access controller, said Carr. In addition, he said, the AD9779 is particularly attractive for direct-conversion radio designs.
The devices run off 1.8 or 3.3 V and consume 600 mW at 500 Msamples/s and 1 W at 1 Gsample/s, said Carr. At an output frequency of 70 MHz and 800 Msamples/s, the SFDR is given as 87 dBc. The two-tone intermodulation distortion is 88 dBc, also at 800 Msamples/s but at 100-MHz output. "That's a 10- to 17-dB advantage," he said.
The AD9444 A/D converter is in production, priced at $38 each per 1,000. The AD9779 D/A converter, which is also available in 12- and 14-bit versions, is sampling, with production scheduled for February. Pricing is set at $28, $25 and $20 for 16-, 14- and12-bit versions, respectively, in lots of 1,000.