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Audio multiplex decoder chip for TV broadcasting

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Renesas Technology has released the R2S15500SP audio multiplex decoder chip for NICAM*1/A2*2 audio multiplex systems, used in TV broadcasting in Europe and Asia. Sample shipments will begin in December 2006, in Japan.

The R2S15500SP converts an audio multiplexed SIF (sound intermediate frequency) signal from a tuner to digital data with an A/D converter, performs processing, and outputs a demodulated audio signal.
The R2S15500SP offers the following main features: 

(1) Support for audio multiplex systems in Europe and Asia
The R2S15500SP supports NICAM/A2/FM monaural/AM monaural audio multiplex signals, enabling demodulation of audio multiplex broadcasting such as stereo and bilingual broadcasts in various regions of Europe and Asia. 

(2) Small low-pin-count package
A small 24-pin SSOP package is used, enabling the board area to be reduced. This package is also suitable for tuner packs, and so forth that require a small mounting area. 

(3) Support for both analogue and digital interfaces
The R2S15500SP incorporates a digital interface and a delta-sigma type D/A converter, enabling a digital demodulated audio signal to be output as either a digital signal or an analogue signal. The digital interface not only handles output, but by inputting an I2S/MSB-first left-justified/ MSB-first right-justified format digital signal, also enables analogue output by means of the on-chip delta-sigma type D/A converter.

By this means, analogue signals and digital signals can be supported for both input and output, allowing flexible adaptation to system specifications.

Product Background
In analogue TV broadcasting, not only monaural broadcasts, but also stereo and bilingual broadcasts are implemented by means of audio multiplexing. There are four main audio multiplex systems worldwide, NICAM, A2, BTSC, and EIAJ, with the system used differing by country or region.

We are now in a period of transition from analogue to digital TV broadcasting, and it is essential for digital broadcast compatible TVs to also be capable of receiving analogue broadcasts. Consequently, there is a definite need for an audio multiplex decoder to offer functions necessary not only for conventional analogue broadcast compatible TV systems, but also for digital broadcast compatible LCD, PDP, and suchlike flat-panel display TV systems.

Meanwhile, EIAJ and BTSC are used in the NTSC broadcasting systems of Japan and the US, capable of being implemented by inexpensive analogue chips, and progress is being made in incorporating the necessary functions in tuners. On the other hand, the NICAM and A2 systems used in Europe and Asia require digital processing, and incorporation into a separate post-demodulation audio signal processing chip or the like has been the mainstream approach. 

However, with this method, it is necessary to redesign the circuitry of the audio signal processing section when the audio multiplex system changes, leading to higher development costs. Thus, in response to these market needs, Renesas Technology has developed R2S15500SP NICAM/A2 compatible audio multiplex decoder chip as an easy-to-use, stand-alone product providing only a decoding function, thereby enabling commonality of subsequent-stage audio signal processing to be achieved, and facilitating low-cost development of TV systems for use throughout Europe and Asia.

Additional Product Details
The R2S15500SP automatically optimises an SIF signal input from a tuner for on-chip A/D converter input by means of an on-chip automatic gain controller (AGC). It is therefore not necessary for the user to be aware of SIF signal input adjustment, and circuitry can be simplified.

A signal converted to 24-bit digital data by the A/D converter undergoes detection and demodulation, in accordance with a particular audio multiplex system. With the NICAM system, NICAM carrier detection and decoding, and analogue (FM or AM) carrier detection and demodulation, are performed. With the A2 system, detection and demodulation of two split carriers (FM1 and FM2), and demodulation and determination of an FM2 carrier ID signal, are performed. With the FM stereo system, aural carrier detection and FM demodulation, pilot carrier detection and determination, and (L-R) carrier AM modulation, are performed. An audio signal thus demodulated is output as a digital signal by means of the digital interface, or as an analogue signal by means of the on-chip delta-sigma type D/A converter.

The R2S15500SP also includes a function that is useful, when post-demodulation audio signal processing is performed by a DSP (digital signal processor). Smooth connection to a DSP can be achieved by selecting a 36.864 or 33.8688 MHz system clock and performing processing at a 48 or 32/44.1 KHz sampling frequency. An I2C bus*3 is also provided, enabling switching or internal determination state reading to be implemented for a variety of functions.

Renesas Technology will continue to develop products that contribute to TV system integration and price reduction, including products that incorporate these functions in a voice processing DSP or video signal processing chip.


1. NICAM (Near Instantaneous Companded Audio Multiplex) is an audio multiplex system developed by the BBC of the United Kingdom, used in PAL/SECAM TV broadcasting in Europe and Asia.
2. A2 is an audio multiplex system utilizing two FM carriers, used in TV broadcasting in Germany and South Korea.
3. I2C bus (Inter IC Bus) is an interface specification proposed by Royal Philips Electronics of the Netherlands.         

Typical Applications
NICAM/A2 TV broadcast compatible TV systems, etc.

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