U4090B

U4090B Monolithic Integrated Feature Phone Circuit Description The µc controlled telephone circuit U4090B is a linear integrated circuit for use in feature phones, answering machines and fax machines. It contains the speech circuit, tone ringer interface with dc/dc converter, sidetone equivalent and ear protection rectifiers. The circuit is line powered and contains all components necessary for amplification of signals and adaptation to the line. An integrated voice switch with loudspeaker amplifier allows loudhearing or handsfree operation. With an anti-feedback function, acoustical feedback during loudhearing can be reduced significantly. The generated supply voltage is suitable for a wide range of peripheral circuits. Features D D D D D D D D D D D D D D D DC characteristic adjustable Transmit and receive gain adjustable Symmetrical input of microphone amplifier Anti-clipping in transmit direction Automatic line loss compensation Symmetrical output of earpiece amplifier Built-in ear protection DTMF and MUTE input Adjustable sidetone suppression independent of sending and receiving amplification Speech circuit with two sidetone networks Built-in line detection circuit Integrated amplifier for loudhearing operation Anti-clipping for loudspeaker amplifier Improved acoustical feedback suppression Power down D Voice switch D Tone ringer interface with dc/dc converter D Zero crossing detection D Common speaker for loudhearing and tone ringer D Supply voltages for all functiona...