AD9761

The AD9761 is a complete dual channel, high speed, 10-bit CMOS DAC. The AD9761 has been developed specifically for use in wide bandwidth communication applications (e.g., sprea
spectrum) where digital I and Q information is being processed during transmit operations. It integrates two 10-bit, 40 MSPS DACs, dual 2·  interpolation filters, a voltage reference, and
digital input interface circuitry. The AD9761 supports a 20MSPS per channel input data rate that is then interpolated by 2·  up to 40 MSPS before simultaneously updating each DAC.

The interleaved I and Q input data stream is presented to the digital interface circuitry, which consists of I and Q latches as well as some additional control logic. The data is de-interleaved back into its original I and Q data. An on-chip state machine ensures thproper pairing of I and Q data. The data output from each latch is then processed by a 2·  digital interpolation filter that eases the reconstruction filter requirements. The interpolated output of each filter serves as the input of their respective 10-bit DAC.

The DACs utilize a segmented current source architecture com bined with a proprietary switching technique to reduce glitch energy and to maximize dynamic accuracy. Each DAC provides
differential current output thus supporting single-ended or differential applications. Both DACs are simultaneously up-dated and provide a nominal full-scale current of 10 mA. Also, the full-scale currents between each DAC are matched to within 0.07 dB (i.e., 0.75%), thus eliminating the need for additional gain calibration circuitry.

The AD9761 is manufactured on an advanced low cost CMOS process. It operates from a single supply of 2.7 V to 5.5 V and consumes 200 mW of power. To make the AD9761 complete it
also offers an internal 1.20 V temperature-compensated bandgap reference.