Power Circuit Board Chips U209B Monolithic Integrated Control Circuitboard

Power Circuit Board Chips U209B Monolithic Integrated Control Circuitboard

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

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

Benefits

Savings of one piezo electric transducer

Complete system integration of analog signal processing on one chip

Very few external components

Applications

DC line interface and supply voltage generation

The DC line interface consists of an electronic inductance and a dual port output stage, which charges the capacitors at VMPS and VB. The value of the equivalent inductance is given by L = RSENSE CIND (RDC R30) / (RDC + R30)In order to improve the supply during worst case operating conditions two PNP current sources - IBOPT and  IMPSOPT - hand an extra amount of current to the supply voltages, when the NPNs in parallel are unable to conduct current. 

A flowchart for the control of the current sources (figure 5) shows, how a priority for supply VMPS is achieved.