A 5-V CMOS programmable acoustic front-end for ISDN terminals and digital telephone sets

A 5-V CMOS programmable acoustic front-end IC for ISDN terminal and digital telephone set applications is presented. The chip performs PCM codec and filter functions, fulfilling all D3/D4 and CCITT specs. Moreover, it implements the main analog interfaces required for the speech channel (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 four wire separated control interface or by means of a serial control channel multiplexed with the PCM voice/data channel in a GCI compatible format. Chip area is 30 mm ² in a 1.5-μm CMOS technology. The active/stand-by power consumption is 60 mW/0.2 mW from a single 5-V supply. All circuits are designed to meet performance objectives over a voltage range from 4.5 V to 5.5 V and a temperature range from -40°C up to 85°C