GENERAL DESCRIPTION

   The  BL34018  Speakerphone  integrated  circuit  Incorporates  the  necessary  amplifiers,

attenuators, and  control  functions  to  produce  a  high  quality  hands  free  speakerphone

system. Include are a microphone amplifier, a power audio amplifier for the speaker, transmit and receive attenuators,a monitoring system for background sound level, and an attenuation control system which responds to the relative transmit and receive levels as well as the  background level.

FEATURE

Voice switched speakerphone circuit.

All necessary level detection and attenuation controls for a hand-free telephone included.

Background noise level monitoring with long time constant.

Background sound level compensation for transmit and receive levels as well as the background level.

Wide operating dynamic range through signal compression.

On-chip supply and reference voltage regulation.

Power audio amplifier for typical 100mW output (into 25 ohms) with peak limiting for speaker to minimize distortion.

Chip Select pin for active/stand by operation.

Linear Volume Control Function.