CODEC for echo-canceling, full-rate ADSL modems

A CODEC, fabricated in 3.3-V CMOS, provides the low-voltage transmitter and receiver interfaces between the modem digital signal-processing engine and the high-voltage hybrid circuitry for either the central office or the rem ote terminal ends of the subscriber loop, configurable by metal mask option . Extensive use of digital interpolation filters in the transmitter, decima tion filters in the receiver, and oversampled data converters minimize the complexity of analog filters. On-chip filtering and 14-bit data converters support echo-canceling modems without requiring external filters. With addi tional external filters, frequency-division duplexing is also supported. Th e die area is 67.5 mm(2). The-power dissipation in the central office and r emote terminal are 600 and 760 mW, respectively.