D/A converter blazes at 1.2 GSPS with 14-bit resolution

Norwood, MA – Analog Devices Inc., a global provider in high-performance semiconductors for signal-processing applications and market leader in data converters, today launched the industry's first 14-bit digital-to-analog converter (DAC) to clock at a sample rate of 1.2 GSPS (giga-samples-per-second). This converter sets a new data-rate benchmark, breaking the 1000 MSPS speed barrier, while still providing superb dynamic performance. As signal processing requirements increase in speed and complexity, electronic engineers are requiring data converters that can synthesize high-quality signals at much higher frequencies. The AD9736 represents a substantial leap in speed and performance. The extremely fast data rates are made possible by the integration of LVDS digital interface technology with Analog Devices' best-in-class high-speed data converters.

In addition to speed, the AD9736 features the lowest power dissipation of any high-speed 14-bit DAC available today, making it ideal for applications that require a low-power DAC to process high frequency and wide synthesis bandwidth signals. These applications include high-bandwidth test and measurement equipment; automatic test equipment; radar; avionics; and wideband communications, such as point-to-point wireless, LMDS (local multipoint distribution systems), and power amplifier linearization. The AD9736 operates from 1.8-V and 3.3-V supplies, consuming 380 mW at 1.2 GSPS with the interpolation filter bypassed, and 550 mW with the interpolation filter enabled.

The AD9736 provides a fast low-voltage differential signaling (LVDS) input interface using a double-data-rate (DDR) mode, which enables high conversion rates over a wide bandwidth. This allows it to receive data at a high speed, while maintaining low distortion and noise, simplifying the transmit signal chain and enabling high quality synthesis of wideband signals at intermediate frequencies up to the Nyquist rate (one half of DAC sampling rate).

The AD9736, a new member of Analog Devices' industry-leading TxDAC+ family of transmit DACs, is joined by pin-compatible 12-bit (AD9735) and 10-bit (AD9734) versions. Operating at 1.2 GSPS, these devices feature a 2X digital interpolation filter, which doubles the incoming sample rate from DSPs, ASICs or FPGAs. This allows designers to take full advantage of the DAC sample rate with existing digital technology, while future-proofing the design. A novel clock-to-data synchronization scheme simplifies the interface timing and enables the extreme sample rate to be realized.

Like all high-speed DACs from Analog Devices, conversion in the AD9736 is initiated on the rising edge of each input clock at the full DAC sample rate. Sampling only on the rising clock edge eliminates potential performance problems related to clock duty cycle sensitivity. DACs that sample on both rising and falling clock edges can exhibit noise feedthrough of the half-rate clock if a nearly perfect 50 percent duty cycle is not maintained. Even small variations in duty cycle can create significant half-rate spurs and images that degrade SFDR (spurious free dynamic range) performance over the Nyquist bandwidth. The AD9736 clocking architecture renders it largely insensitive to clock duty cycle variations.

The output currents of the AD9736 can be programmed over a range of 10 mA to 30 mA, and can be easily configured for various single-ended or differential circuit topologies. The device's IMD is 74 dBc at an output frequency of 255 MHz and better than 65 dBc up to a 600 MHz output frequency. SFDR is 63 dBc at a 300 MHz output frequency and 53 dBc at 600 MHz, sampling at 1.2 GSPS. Noise performance is excellent, with noise spectral density of “158 dBm/Hz synthesizing a 300-MHz output.

The 14-bit AD9736 is sampling now. The device is offered in a 160-pin BGA (ball grid array) package to reduce parasitics and improve performance. Production quantities for the AD9736, AD9735, and AD9734 will be available at the end of 2004. In 1,000-piece quantities, the AD9736 is priced at $34.95; the pin-compatible 12-bit AD9735 is $19.95, and the 10-bit AD9734 is $14.95.

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