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Car audio LSI promises home-theater sound quality

Posted: 12 Jul 2007 ?? ?Print Version ?Bookmark and Share

Keywords:car audio LSI? car audio processor? home-theatre sound quality?


Rohm Co. Ltd has developed a high-performance, high-quality audio processor LSI chip that promises the same sound quality as home theater systems while greatly reducing shock noise generated when switching volume or tone. Two models are currently available: the BD3484FS with a built-in loudness function, and the BD3489FS that integrates a six-channel external I/O terminal capable of connecting directly to DSP.

A new advanced switching circuit automatically calculates the optimal number of gain switching steps from the input signal level and gain change value, resulting in a smoother envelope waveform, eliminating shock noise generated during switching when silent at 20Hz low audio signal input and at 2Vrms high audio volume input. Another feature of the advanced switching circuit is the reduced load it places on the MCU. Current software switching methods must constantly send gain setting values to the sound processor LSIaccurately timed with the MCUuntil gain conversion was completed. This not only places an additional load on the MCU but increases production time due to software development. Rohm's advanced switching circuit integrates register circuits that require changed values to be sent only once, after which optimum gain change processing is performed automatically, eliminating MCU load while simplifying software development.

The BD3484FS and BD3489FS devices feature different functions for level meter display and spectrum analyzer display outputs but were designed to be compatible with Rohm's multichannel sound processor LSI series regarding pin placement and register maps. Bass programs such as input selector, input gain and volume gain are shared in common with other sound processor LSI series, even when set functions are ranked or changed according to product destination, making them compatible with most other sound processor LSIs and CPU software. This results in shorter, more efficient program development and use of common baseboard design. Both products utilize expertise gained from years of experience in audio LSI development to achieve a distortion of 0.007 percent and an output noise voltage of 10.5Vrms, ensuring the highest level of sound quality.

Key specifications of the devices include advanced switching technology which greatly reduces switching noise (shock noise) generated from gain attenuation in volume and quality and an I?C bus register map which is compatible with previous Rohm sound processor LSIs.

BD3484FS and BD3489FS also has a pin placement feature that is compatible with previous Rohm sound processor LSIs, enabling use of common base boards. The devices integrate a built-in LPF for equalizer filter and subwoofer significantly reduces the number of external components required. The subwoofer connection is being supported for more natural, realistic sound. Both devices are equipped with an effective external input terminal for sound quality correction such as BBEIC or DSP, for added value. The BD3484FS device in particular is capable of adjusting for optimal loudness frequency based on vehicle interior.

Sample shipments of both products are now available and are priced at $8 each. Volume quantities will be available in August.

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