DACs deliver fast throughput, low noise

Norwood, Mass. — The AD974x and AD978x families are the latest additions to Analog Devices' TxDAC portfolio of digital-to-analog converters (DACs) optimized for the transmit signal path of communications systems. The two-channel, high-speed DACs include the AD974x family of 8-, 10,-, 12-, 14-, and 16-bit devices with sample rates up to 250 million samples per second (MSPS) using low-voltage CMOS (LVCMOS) inputs. The AD978x family of 12-, 14-, and 16-bit DACs, which use low-voltage differential signaling (LVDS) inputs, achieve sample rates as fast as 600 MSPS.

Offering low noise and low intermodulation distortion, the AD974x and AD978x TxDAC devices are said to offer best-in-class W-CDMA adjacent-channel leakage ratio (ACLR) performance of 80 dBc at 61.44 MHz, which is a 5 dBc improvement over the nearest competitive transmit DACs, according to ADI.

The TxDAC ICs are aimed at many wideband communications standards including GSM, W-CDMA, CDMA2000, TD-SCDMA, WiMAX, LMDS/MMDS, and point-to-point wideband. They are also designed for instrumentation applications such as RF signal generators, automated test equipment and ultrasound systems.

The AD974x and AD978x families integrate a new mixer function that provides designers with a usable output beyond Nyquist frequency. In the “normal mode,” the signal in the first Nyquist zone is strongest. In the “mixer mode,” the DACs can directly generate RF signals by boosting the signal power in the second and third Nyquist zones. This allows designers to eliminate a mixing stage, reducing component count
and design complexity in direct-RF applications, said Analog Devices.

The AD974x and AD978x families also integrate two auxiliary DACs that can be used to compensate for TxDAC device or mixer offset errors without adding external components. The DACs operate from 1.8-V and 3.3-V power supplies and offer power dissipation of 315 mW. The devices are pin-compatible and interface to analog quadrature modulators such as Analog Devices' ADL5370.

Pricing: From $14.59 per unit in quantities of 1,000.
Availability: Available in 72-lead LFCSP packaging, the AD974x (AD9741/42/45/46/47) and AD978x (AD9780/81/83) TxDAC families are available now in full production quantities.
Product information: AD974x and

Analog Devices, Inc. , 1-800-ANALOGD or 1-800-262 5643,

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