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Synthesizer ICs with on-chip 14-bit DACs tout 1 GSPS operation

Norwood, Mass.&#8212Analog Devices says it has more than doubled the clock speed of the industry's fastest direct digital synthesizer (DDS) ICs that use 14-bit digital-to-analog converters.

As such, the AD9910 and AD9957, for frequency agile applications such as wireless base stations, military
and commercial radar, test equipment, and secure communications systems, are touted as the first DDS devices with integrated 14-bit DACs to achieve speeds of 1 gigasamples per second (GSPS), while lowering power consumption by more than 50 percent.

The 1 GSPS operating speed and the 14-bit DAC in the AD9910 DDS, which is suited to communications and instrumentation applications, facilitates an improvement in dynamic performance for output frequencies to 400 MHz. The second device, the AD9957 DDS modulator (or quadrature digital upconverter, QDUC) simplifies data transmission for wired and wireless systems by offering real outputs up to 400 MHz.

“Increasing clock speeds to 1 GSPS on high-resolution DDS ICs allows our customers to generate higher output frequencies with improved dynamic performance,” said Kevin Kattmann, product line
director, High Speed Signal Processing Group, Analog Devices. “The new DDS products represent a significant step forward, providing 8 to 12 dB better spurious free dynamic range (SFDR) when compared to previous
generations.”

The AD9910 and AD9957 are the company's first devices developed on a new, low-power DDS core that consumes only one-tenth the power of previous
generation cores. It's based on technology licensed from Pentomics, a California-based company that specializes in circuit design and signal processing for digital communications. Featuring a 16-bit parallel port with update rates to 250 MHz, the AD9910 digital synthesizer allows designers to update a 32-bit frequency tuning word every 8 ns. Thus it's suited for high-speed waveform generators, frequency hopping synthesizers, secure communications, and a variety of radar and scanning systems.

In addition, the AD9910 offers a 70 percent reduction in power dissipation when compared to existing solutions, consuming just 700 milliwatts at full operating speed. The enhanced on-chip reference clock multiplier reduces system cost by generating the internal 1 GSPS
clock from a low frequency external source. Additional
features added to the DDS core include a secondary accumulator for linear sweeping of frequency, phase or amplitude; RAM for user-defined non-linear sweeping; and ease of synchronization for multiple DDS devices in the same system. The AD9910 may be combined with the company's ADCMP60x comparators or AD951x clock dividers to generate programmable high-speed, low-jitter clock solutions.

The AD9957 QDUC integrates a high-speed DDS, a 14-bit DAC, clock multiplier circuitry and digital filters on a single chip, enabling uncomplicated, cost-effective baseband up-conversion for data transmission in wired or wireless communications infrastructure systems, including WiMAX applications. The QDUC achieves greater than 50 percent power reduction (down to ~1.3 watts at 1 GSPS) over existing QDUCs.

The chip receives an interleaved I/Q data stream, interpolates it, and synthesizes the desired signal for transmission. The 1 GSPS numerically controlled oscillator (NCO) and DAC allow the AD9957 to provide direct outputs up to 400 MHz, thus eliminating some up-conversion stages and reducing filter requirements.

The chip's low-noise, on-chip reference clock multiplier allows the use of low-cost, low-frequency sources for the system clock while still delivering excellent dynamic performance. The AD9957 also supports test vectors and amplitude ramping capability. The user interface to
the control functions of the AD9957 includes a serial port easily configured to work with ADI's Blackfin processors.

Click here and here for additional information on the AD9910 and AD9957, respectively. The AD9910 and AD9957, in 100-lead quad flat packs, are sampling now with full-production quantities available in February. The AD9910 is priced at $35 per unit in 1k pieces. The AD9957 is priced at $21 each.

Analog Devices , 1-800-ANALOGD, www.analog.com

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