Producing antenna frequencies directly out of the transmit DAC is a big step closer to enabling the software-defined radio (SDR). This is due to the wide bandwidth and effective dynamic range of the DAC coupled with the ability to support a wide range of output frequencies that covers nearly all of the wireless infrastructure standards. Achieving direct RF output from the DAC saves board space by eliminating upconvert mixer stages and filters and saves power by enabling the use of a real versus complex architecture scheme.

The new AD9739, a 14-bit, 2500 MSPS TxDAC® transmit DAC, makes generating a direct RF output a reality. The AD9739 features ADI's highest performance DAC core, coupled with MixMode® super- Nyquist operation that enables direct RF outputs at up to 2.5 GHz and 3.6 GHz in the third Nyquist zone. This mode provides internal digital processing that allows output frequency placement into the second and third Nyquist zones without the traditional sin(x)/x roll-off in signal amplitude. In fact, with the mixer mode function enabled, the power of the images located in the second and third Nyquist zones are boosted to be the strongest in the output spectrum. A band-pass filter can be employed to select either the upper or lower side band signal as the signal of interest. This approach effectively eliminates a mixer stage from the system, reducing cost and board area.

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The AD9739 also operates as a traditional high performance DAC, generating wideband signals up to 1 GHz with an SFDR of 60 dB at 950 MHz output. The device includes a dual-bus LVDS interface with on-chip termination, which is interleaved internally into a single datapath to the DAC. This feature eases the interface speed requirements down to 625 MHz double-data rate (DDR) at a DAC sampling rate of 2500 MSPS with DDR. The AD9739 is also power efficient, drawing only 1.1 W when running at its full sampling rate. The device is packaged in 160-lead CSP_BGA.

Power Efficient Dual, High Speed ADC Targets Communications, Industrial, Portable, and Instrumentation Applications

The AD9268 is the industry's first dual channel, 16-bit, 125 MSPS ADC, and it consumes only 376 mW per channel—60% less power per channel than competing devices. This new ADC's integration and energy savings allow system engineers to increase system channel counts without increasing a product's board area or power consumption, enabling higher call volume in cellular base stations, for example, or improved image resolution in medical magnetic-resonance imaging (MRI) equipment. In portable applications, the AD9268 likewise enables improved system performance while extending battery life in handheld instruments and test equipment, such as portable spectrum analyzers.

The AD9268 ADC is available in speed grades of 80 MSPS, 105 MSPS, and 125 MSPS. The 125 MSPS option achieves 78.2 dBFS signal-to-noise ratio (SNR) and 88 dB spurious-free dynamic range (SFDR) to 70 MHz analog input frequency, while consuming 376 mW per channel. It operates from a single 1.8 V analog power supply and features a high performance, sample-and-hold circuit and on-chip voltage reference. The device is compatible with ADI's dual channel variable gain amplifiers (VGAs), including the AD8372 programmable dual VGA and AD8376 IF dual VGA, as well as the ADL5561 differential RF/IF amplifier and ADL5562 differential RF/IF amplifier. Recommended clock generators include the AD9520-0 and AD9522-0.

AD9268 Features

• 376 mW per channel @ 125 MSPS
• 78.2 dBFS SNR; 88 dB SFDR
• Operation from a single 1.8 V supply
• 1.8 V CMOS or LVDS outputs
• Integer 1-to-8 clock divider
• Multichip sync function and SPI-based user controls

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