The Analog Devices’ AD9739 primarily targets wireless infrastructure transmit applications like basestations. The AD9789 also can be used in wireless but is more targeted at cable TV head-end infrastructure using DOCSIS 3.0.

The AD9739 and AD9789 digital-to-analog converters (DACs) from Analog Devices can translate 14-bit words into analog signals at frequencies to 3.6 GHz, suiting them for the transmit function in new cellular basestations and point-to-point wireless applications (see the figure).

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The AD9739 has a 10-, 12-, or 14-bit switched current-source DAC with dual-port low-voltage differential signaling (LVDS) inputs and a current reference on board. Its word update is good to 2.5 Gbits. Also, the DAC supports a bandwidth of just over 1 GHz. Its serial peripheral interface (SPI) is used for configuration and status register read back. Consuming a maximum of 1.1 W, it offers an 80-dBc adjacent channel leakage ratio (ACLR) at 350 MHz and 90-dBc intermodulation distortion (IMD) at 350 MHz.

The AD9789 has the same DAC core as the AD9739 but also includes signal processing in the form of four channels of quadrature amplitude modulation (QAM) encoding with square-root raised cosine (SRRC) filters with interpolation filters, rate converters, and modulators. The input can be configured for bit sizes from 4 to 32 bits. The QAM encoders support constellation sizes of 16, 32, 64, 128, and 256.

While the AD9789 is useful in wireless applications, it also targets the cable TV infrastructure building DOCSIS 3.0 cable modem termination system (CMTS) headends. It permits up to four contiguous 6-MHz DOCSIS channels to be synthesized and placed anywhere in the DOCSIS band. Typical specs include 75-dBc ACLR at 250 MHz and 1.6-W power dissipation.

Both devices provide multicarrier capability up to the Nyquist frequency in baseband mode and offer a mix-mode function to generate RF signals in the second and third Nyquist zones. This feature enables designers to eliminate a mixer stage while reducing component count and design complexity in direct RF applications.

Also, both devices are made with 180-nm CMOS and operate from 1.8 to 3.3 V. The AD9739 comes in a chip-scale ball-grid array (CSBGA) package with 160 pins and costs $43.69 in 1000-unit quantities. The AD9789 comes in a 164-pin CSBGA and starts at $53.10 in 1000-unit volume. The products are sampling now.

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