TEA0679T

General description

The TEA0679T is a bipolar integrated circuit that provides two channels of Dolby B noise reduction for playback applications in car radios. It includes head and equalization amplifiers with electronically switchable time constants. The device also includes electronically switchable inputs for tape drivers with reverse heads.

This device detects pauses of music in the Automatic Music Search (AMS) scan mode (for applications with an intelligent controlled tape driver) or AMS latch mode (for applications with a simple controlled tape driver).

For both modes the delay time can be fixed by using an external resistor. In the blank skip mode the IC can detect pauses of music during playback and allows a microcontroller to react on this situation.

The equalization amplifier gain adjustment, the output offset adjustment and all switching functions are I²PC-bus controlled. Head switching and equalization time constant switching can be controlled via separate pins (optional). The device operates with power supplies from 7.6 to 12 V. The output overload level increases with increases in supply voltage.

Current drain varies with the following variables:

• Supply voltage
• Noise reduction on/off
• AMS on/off.

Because of this current drain variation it is advisable to use a regulated power supply or a supply with a long time constant.

Features

• Dual Noise Reduction (NR) channels
• Head preamplifiers
• Reverse head switching
• Automatic Music Search (AMS)
• Blank skip
• Mute position
• Equalization with electronically switched time constants
• Switch functions and level adjustment controlled via I²PC-bus
• Optional switch inputs TTL compatible
• Dolby reference level = 387.5 mV
• Contained in a 32-pin small outline package
• Improved EMC behaviour.

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