An Analog / Digital Front - End CMOS IC for ISDN

Using a 4 ¿m silicon-gate CMOS technology a mixed analog-digital multi-function chip has been developed, which enables the digital access to and from the subscriber line as part of an ISDN (Integrated Services Dig ital Network) interface module. The transmit path of the chip incorporates a I4th-order digital FIR filter, a D/A converter and a power opamp which drives the subscriber line. In the receive path an interpolative A/D converter gives the high accuracy which is prerequisite for effective digital echo cancellation. Various additional features like power-down capability with wake-up signal detection will ease the design of the complete ISDN interface module.