ADI chip combines direct digital synthesizer with DAC

A single-chip device from Analog Devices Inc., the AD9858, combines a 1GSa/s direct digital synthesizer (DDS) with a 10-bit, 1GSa/s DAC, 2GHz RF analog mixer, a 150MHz phase frequency detector, and a programmable charge pump with proprietary fast-locking acquisition logic.

Designed for wireless basestations as well as military and aerospace radar applications, the AD9858 is said to offer fast frequency hopping and fine-tuning. Dan Savignon, marketing engineer of signal synthesis products at Analog Devices, said the device compares favorably with a predecessor, the AD9852, which operates at less than one-third the speed (300MSa/s) and consumes more power (2.2W vs. <2W for the new device).

"By integrating a DAC, phase/frequency detector and charge pump, the AD9858 meets customer requirements for low phase noise, low spurious energy, fast frequency switching and a wide-bandwidth linear sweeping capability," Savignon said. In wireless basestation applications, the DDS provides a lower-cost platform for fast-hopping synthesizers that do not need isolation switches.

The DDS can generate frequencies of 400MHz and higher when driven at a 1GHz internal clock speed. The reference clock can be derived from an external clock source of up to 2 GHz, using an on-chip divide-by-2 feature. The on-chip mixer and PFD/charge pump enable a variety of synthesizer configurations for generating frequencies in the 1GHz to 2GHz range or higher.

The AD9858 is available in a 100-lead EPAD-TQFP, priced at $49.50 in 1,000-piece quantities. Additional information is available at www.analog.com/AD9858.

EE Times