A 5V CMOS Programmable Acoustic Front-End for ISDN Terminals and Digital Telephone Sets

Abstract

A 5V programmable acoustic front-end IC for ISDN terminal and digital telephone set applications is presented. The chip performs PCM codec and filter functions fulfilling and exceeding all D3/D4 and CCITT specs. It implements the analog interfaces required for the speech (low noise microphone preamplifier, earpiece and loudspeaker drivers, sidetone, antilarsen control) and tone/ring/DTMF generation without external components. The device can be controlled by a microprocessor or a HDLC controller via a separate four wire control interface or by means of a serial control channel multiplexed with the PCM voice/data in a GCI compatible format. Chip area is 30 mm2 in a 1.5¿ CMOS technology. Active/stand-by power consumption is 60mW/0.2mW from a single 5V supply.