News | January 12, 2005

Analog Devices Doubles 16-Bit Converter Speed To One Billion Samples Per Second


Norwood, MA -- Analog Devices today introduced a 16-bit digital-to-analog converter (DAC) that achieves a sample rate of 1 GSPS (giga-samples-per-second). At these speeds, the AD9779 maintains signal-processing performance in terms of dynamic range, noise, and distortion, while consuming up to 36% less power. The highly integrated interpolating dual AD9779 is designed to enable high quality conversion of W-CDMA, CDMA2000, TD-SCDMA, and WiMAX.

"The requirements of multi-channel wireless communications applications and digital predistortion architectures are driving the need for more optimized data converters that can synthesize high-quality signals at much higher frequencies," said Dave Robertson, product line director, High-Speed Converters, Analog Devices. "With the AD9779, Analog Devices is delivering a dual 16-bit DAC that offers wireless systems designers the best combination of signal processing performance, low-noise and low-power consumption for wideband signal synthesis. This combination allows communications infrastructure manufacturers to design one transceiver platform for the global deployment of multiple wireless standards."

Pin-compatible family of transmit signal path converters
In addition to the AD9779, Analog Devices is introducing the AD9778 and AD9776 dual interpolating DACs, forming a family of 16-/14-/12-bit pin-compatible devices that allow designers to easily trade off performance for system cost. These devices are the newest members of Analog Devices' TxDAC portfolio of digital to analog converters specifically optimized for the transmit signal path of communication systems.

About the AD9779
According to Analog Devices, the 16-bit AD9779 dual DAC offers 4 dB lower noise, 15 dB better intermodulation distortion (IMD), and 20 dB higher spurious free dynamic range (SFDR) than competing products at a 70 MHz output frequency while consuming 600 mW of power at 500 MSPS and 1 W at 1 GSPS. The device contains on-chip digital interpolation filters, a complex digital modulator, and a digital mixer. These features simplify the digital interface and allow some digital signal processing functions to be moved out of the FPGA or ASIC. Another benefit of the on-chip filtering is relaxation of the analog reconstruction filters, which eases performance requirements to reduce board space and total system cost while improving manufacturability.

As a dual DAC, gain and offset matching in the AD9779 is guaranteed, making the device appropriate for direct conversion or imag- reject architectures using an analog quadrature modulator. Integrated gain and offset calibration DACs enable communications equipment designers to optimize sideband rejection and local oscillator (LO) feedthrough in these architectures. A multi-DAC synchronization scheme simplifies clocking requirements in systems with multiple converters, allowing easier control of phase coherency. Device configuration is achieved through an easy-to-use serial peripheral interface (SPI) with an interface common to other TxDAC devices.

Building a complete signal chain
For optimized transmit signal chain performance, the analog output of the AD9779 TxDAC converter seamlessly interfaces to Analog Devices' analog quadrature modulators, such as the AD8349. A standard parallel interface enables straightforward connection to the AD6633 multi-channel wideband up converter with the VersaCREST crest reduction engine. The AD9779 can be driven by ADI's AD9510 high-performance clock distribution IC as part of a complete clock distribution system. ADI's latest 14-bit, 80 MSPS analog-to-digital converter (ADC), the AD9444, is designed to interface to the AD6636 4-/6-channel digital downconverter to form the core of a wideband communications receiver (see related story). Together, these devices form the basis for a high-performance digital radio transceiver.

The AD9779, AD9778, and AD9776 TxDAC converters are sampling now and will be available in production quantities in May 2005 in a Pb-free 100-lead TQFP_EP (Thin Quad Flat Pack_Exposed Paddle) package.

Source: Analog Devices