U4080B

U4080B Voice-Switched Circuit for Handsfree Operation Description The voice switched speakerphone integrated circuit, U4080B, incorporates a variety of functions (see below). The versality of the device is further enhanced by the provision of a large number of pins giving access to internal circuit points. Features D Operates on telephone lines, integrated reference voltage regulation D Output power: 100 mW at a 25-Ω load with peak limitation D Linear volume control D Monitoring system for background sound level D Wide operating dynamic range through signal compression D Chip select pin for active/standby operation Block Diagram / Application Circuit Figure 1. Block diagram and application circuit TELEFUNKEN Semiconductors Rev. A1, 20-May-96 1 (15) Preliminary Information U4080B Pin Description Pin 1 Symbol Function R1 Load resistance. Pin 14 Symbol Function GND1 High current ground pin for the speaker 2 RTG 3 4 TI TO 5 TLI 6 TLO 7 RLI 8 RLO 9 MIC 10 MICO 11 CP1 12 CP2 13 TDI Provides reference current for the transmit and receive attenuators. Transmit attenuator nominal gain resistor. Transmit channel gain is inversely proportional to the resistance RTG connected to Pin 2. Transmit attenuator input. Input resistance is 5 kΩ Transmit attenuator output. Drives the input of the transmit level detector and the external circuit which drives the telephone line. Transmit level detector input. Sets the detector level. Sensitivity to transmit channel ...