U4090B

· 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
· Voice switch
· Tone ringer interface with dc/dc converter
· Zero crossing detection
· Common speaker for loudhearing and tone ringer
· Supply voltages for all functional blocks of a subscriber set
· Integrated transistor for short circuiting the line voltage
· Answering machine interface
· Operation possible from 10 mA line currents

Feature phone, answering machine, fax machine, speaker phone

The mc controlled telephone circuit U4090B is a linear integrated circuit for use in feature phones, answering machines and fax machines. U4090B 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 U4090B allows loudhearing or handsfree operation. With an anti-feedback function, acoustical feedback during loudhearing can be reduced significantly. The generated supply voltage of U4090B is suitable for a wide range of peripheral circuits.