1. 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．Also included are all necessary regulated voltages for both internal and external circuitry，
allowing line-powered operation (no additional power supplies required)．A chip select pin allows
the chip to be powered down when not in use．A volume control function may be implemented
with an external potentiometer．BL34018 applications include speakerphones for household and
business use，intercom systems，automotive telephones，and others．
Voice switched speakerphone circuit.
All necessary level detection and attenuation controls for a hand-free telephone
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.
3. BLOCK DIAGRAM
Total 16 Pages
Wrote by 2006