GENERAL DESCRIPTION
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.

FEATURES
Line interface
• Low DC line voltage
• Voltage regulator with adjustable DC voltage
• Symmetrical high-impedance inputs (70 kΩ) 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.

APPLICATIONS
• Telephone answering machines
• Telephones with digital handsfree
• Line powered telephone sets
• Cordless telephones
• Fax machines.