TEA1097

Line interface
Low DC line voltage
Voltage regulator with adjustable DC voltage
Symmetrical high-impedance inputs (70 kW) for dynamic, magnetic or electric microphones
Dual Tone Multi-Frequency (DTMF) input with confidence tone on earphone and/or loudspeaker
Receive amplifier for dynamic, magnetic or piezo-electric earpieces (with externally adjustable gain)
Automatic Gain Control (AGC) for true line loss compensation.
Supplies
Provides a strong 3.35 V regulated supply for microcontroller or dialler
Provides filtered power supply, optimized according to line current and compatible with external voltage or current sources
Filtered 2 V power supply output for electret microphone
Compatible with a ringer mode
Power-Down (PD) logic input for power-down.
Loudspeaker amplifier
Single-ended rail-to-rail output
Externally adjustable gain
Dynamic limiter to prevent distortion
Logarithmic volume control via linear potentiometer.
Auxiliary interfaces
Asymmetrical high-impedance input for electret microphone.
General purpose auxiliary output for transmit and receive
Auxiliary transmit input with high signal level capability dedicated to line transmission
Auxiliary receive input with high signal level capability
Integrated multiplexer for channels selection.

The TEA1097 is an analog bipolar circuit dedicated for telephone applications. It includes a line interface, handset microphone and earpiece amplifiers, base microphone and loudspeaker amplifiers, some specific auxiliary Inputs/Outputs (I/Os) and an analog multiplexer to enable the right transmit and/or receive channels. The multiplexer is controlled by a logic circuitry decoding four logic inputs provided by a microcontroller. Twelve different application modes have been defined and can be accessed by selecting the right logic inputs.

This IC can be supplied by the line and/or by the mains if available (in a cordless telephone or a telephone answering machine for example). It provides a 3.35 V supply for a microcontroller or dialler and a 2 V filtered voltage supply for electret microphones. The IC is designed to facilitate the use of the loudspeaker amplifier during ringing phase.