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ST audio amplifier maintains hi-fi sound during engine turn-off and cranking

September 20, 2010 | Christoph Hammerschmidt | 222901487
ST audio amplifier maintains hi-fi sound during engine turn-off and cranking In modern cars, fuel consumption reduction features such as start/stop function frequently challenge the vehicles electronics: When they switch off the engine, the supply voltage in the car can be reduced significantly. STMicroelectronics brings an audio power amplifier to market that operates unaffected by these voltage variations.

STMicroelectronics hast started production of is pioneering of the TDA7850LV, a 4x50W audio power amplifier. The device is the first start/stop-compatible IC of its kind in production, ST claims.

Start-stop systems, seen by many manufacturers as a big contributor to reducing fuel consumption, shut down the engine when the vehicle is stopped, for example at traffic lights, and restarts as the driver prepares to move off. In cars fitted with start/stop, the supply voltage for on-board electrical equipment can fall to as low as 6V when the engine is turned off and restarted and only the battery is supplying electrical power. Switching between battery power and alternator power can generate 'pop and click' noise the audio system's output. Hybrid-electric vehicles present similar challenges to electronic equipment designers.

According to ST, discrete components external to the audio power amplifier can be used to build circuitry to regulate the supply voltage and suppress pop and click noises. However, these circuits complicate design and add significantly to bill-of-materials costs. ST's TDA7850LV audio power amplifier makes the use of all these components unnecessary and therefore simplifies design, reduces cost, and saves pc-board space.

The chip vendor is preparing a family of start/stop audio power amplifiers which will include entry-level class-AB amplifiers, digital devices with diagnostic features, and an automotive class-D family offering outstanding power efficiency.

In addition to start/stop compatibility, the TDA7850LV features ST's Flexiwatt power package – according to the vendor now the de-facto standard for car audio ICs. A variety of configurations are available, including vertically or horizontally mounted packages. In addition, a surface-mount variant allows car-audio makers to take advantage of high-speed fully automated assembly enabling increased throughput and production quality.

Other features include Hi-fi class distortion, low output noise and an integrated high-side driver supporting antenna control and similar functions. The device also incorporates protection against common vehicle electric hazards such as short circuits to ground and battery, open-circuited speakers or overtemperature. 

The TDA7850LV is currently ramping-up mass production, priced at $5.30 for orders of 1000 pieces. Alternative pricing options are available for larger volumes.

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