A CMOS analog front-end IC for DMT ADSL

Abstract

Asymmetric digital subscriber line (ADSL) technology meets the need for high-bandwidth communications to the home utilizing the existing twisted-pair copper. In an ADSL modem, noise and linearity of the analog front end (AFE) are critical to the data rate achievable over the longest lines (up to and above 18 kfeet of AWG24 wire) and hence the fraction of installed lines over which ADSL service can be deployed. In multitone ADSL, dynamic linearity throughout the band determines modem capacity. This highly-integrated CMOS AFE is compatible with both the full ADSL T1E1.413 DMT standard and the emerging G.lite standard, and achieves 14 b linearity in both RX and TX paths and input-referred noise better than -160 dBm/Hz, from a single 5.0 V supply. These noise and linearity specifications are necessary for an ADSL modem to operate at 1.5 Mb/s on the longest lines and reach >90% of installed copper connections.