GENERAL DESCRIPTION

The AD9776/AD9778/AD9779 are dual, 12-/14-/16-bit, high dynamic range, digital-to-analog converters (DACs) that provide a sample rate of 1 GSPS, permitting multicarrier generation up to the Nyquist frequency. They include features optimized for direct conversion transmit applications, including complex digital modulation, and gain and offset compensation. The DAC outputs are optimized to interface seamlessly with analog quadrature modulators such as the AD8349. A serial peripheral interface (SPI?) provides for programming/readback of many internal parameters. Full-scale output current can be programmed over a range of 10 mA to 30 mA. The devices are manufactured on an advanced 0.18 μm CMOS process and operate on 1.8 V and 3.3 V supplies for a total power consumption of 1.0 W. They are enclosed in 100-lead TQFP packages.

FEATURES

Low power: 1.0 W @ 1 GSPS, 600 mW @ 500 MSPS,

full operating conditions

SFDR = 78 dBc to fOUT = 100 MHz

Single carrier WCDMA ACLR = 79 dBc @ 80 MHz IF

Analog output: adjustable 8.7 mA to 31.7 mA,

RL = 25 Ω to 50 Ω

Novel 2×, 4×, and 8× interpolator/coarse complex modulator

allows carrier placement anywhere in DAC bandwidth

Auxiliary DACs allow control of external VGA and offset control

Multiple chip synchronization interface

High performance, low noise PLL clock multiplier

Digital inverse sinc filter

100-lead, exposed paddle TQFP package

APPLICATIONS

Wireless infrastructure

WCDMA, CDMA2000, TD-SCDMA, WiMax, GSM

Digital high or low IF synthesis

Internal digital upconversion capability

Transmit diversity

Wideband communications: LMDS/MMDS, point-to-point