Car audio sound processor featuring high fidelity

ROHM has developed a high-performance, high-quality audio processor LSI chip that provides the same sound quality as home theater systems while greatly reducing shock noise generated when switching volume or tone. Two models are available: the BD3484FS with a built-in loudness function, and the BD3489FS that integrates a 6-channel external input/output 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 microcontroller. Current software switching methods must constantly send gain setting values to the sound processor LSI— accurately timed with the microcontroller— until gain conversion was completed. This not only places an additional load on the microcontroller 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 microcontroller load while simplifying software development.

The BD3484FS and BD3489FS feature different functions for level meter display and spectrum analyzer display outputs but were designed to be compatible with ROHM’s multi-channel 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% and an output noise voltage of 10.5Vrms, ensuring the highest level of sound quality.

ROHM Co., LTD