A BiCMOS analog front-end circuit for an FDM-based ADSL system

This BiCMOS analog front-end (AFE) integrated circuit contains the analog transmit function and a low-noise receiver for FDM-based ADSL systems. The IC includes a current steered 14-bit 5-Msps D/A converter, laser trimmed third-order reconstruction and anti-alias filters, a programmable attenuator with 200-ohm output drive capability, 60-dB of RX programmable gain, and a serial interface. Trimmable thin-film resistors allow /spl plusmn/4% filter cutoff frequency and absolute gain accuracy. The multitone power ratio performance of the part is approximately 65 dB with a spurious free dynamic range >70 dBc. The CMRR of the RX channel is >90 dB@1.1 MHz. PSRR for transmit and receive are greater than 60 dB. The isolation features of the 1.2-/spl mu/m BiCMOS technology allow transmit and receive to operate in full-duplex mode with greater than 80 dB of cross-talk isolation. The chip size is 25.8 mm/sup 2/ which includes bond pads and electrostatic discharge protection devices.