GENERAL DESCRIPTION

The AD9879 is a single-supply set-top box and cable modem mixed-signal front end. The device contains a transmit path interpolation filter, complete quadrature digital upconverter, and transmit DAC. The receive path contains a 12-bit ADC, a 10-bit ADC, and dual 7-bit ADCs. All internally required clocks and an output system clock are generated by the phase-locked loop (PLL) from a single crystal or clock input.

The transmit path interpolation filter provides an upsampling factor of 16× with an output signal bandwidth as high as 8.3 MHz. Carrier frequencies up to 65 MHz with 26 bits of frequency tuning resolution can be generated by the direct digital synthesizer (DDS). The transmit DAC resolution is 12 bits and can run at sampling rates as high as 232 MSPS. Analog output scaling from 0.0 dB to 7.5 dB in 0.5 dB steps is available to preserve SNR when reduced output levels are required.

FEATURES

Low cost 3.3 V MxFE™ for DOCSIS-, EURO-DOCSIS-, DVB-, DAVIC-compliant set-top box and cable modem applications

232 MHz quadrature digital upconverter

12-bit direct IF DAC (TxDAC+™)

Up to 65 MHz carrier frequency DDS

Programmable sampling clock rates

16× upsampling interpolation LPF

Single-tone frequency synthesis

Analog Tx output level adjust

Direct cable amp interface

12-bit, 33 MSPS direct IF ADC with optional video clamping input

10-bit, 33 MSPS direct IF ADC

Dual 7-bit, 16.5 MSPS sampling I/Q ADC

12-bit Σ-∆ auxiliary DAC

APPLICATIONS

Cable modem and satellite systems

Set-top boxes

Power line modem

PC multimedia

Digital communications

Data and video modems

QAM, OFDM, FSK modulation