Audio A/D converter touts eight-channels

Austin, Texas — Cirrus Logic Inc. rolled out an audio analog-to-digital converter (A/D converter) IC that is said to eliminate the need for multiple stereo A/D converters for surround-sound or multichannel applications.

Through feature integration, the CS5368 provides system designers with a space-saving device that streamlines product development, reduces design complexity and lowers overall system cost compared to boards that use multiple stereo A/D converters, said Jason Rhode, vice president of Cirrus' Mixed-Signal Audio Products Division.

The CS5368 is the industry's first eight-channel audio A/D converter to feature a high-speed Time-Division Multiplexing (TDM) interface, which provides a serial output of eight channels of audio data with sample rates up to 192 kHz within a single data stream, Rhode said. This capability reduces layout constraints and relieves input and output constraints on digital signal processors, he said. In addition, low latency digital filtering makes the CS5368 suited for live-sound and real-time audio applications.

The A/D converter is intended for a wide variety of consumer and professional audio applications, such as audio/video receivers, home theater systems, digital mixing consoles, outboard audio converters, PC soundcards, external audio interfaces, DSP amplifiers and various automotive audio systems.

Cirrus Logic also offers the IC in pin-compatible four- and six-channel options (CS5364 and CS5466). Each IC provides dynamic range of 114 dB and a negligible low-noise measurement of -105 dB total harmonic distortion plus noise (THD+N).

The ICs also feature a differential architecture that provides excellent noise rejection and performs sampling, analog-to-digital conversion and anti-alias filtering. Each IC also supports all common PCM and TDM audio formats.

See related block diagram

The CS5368/66/64, which are currently sampling, are available in 48-pin LQFP packages and are priced at $11.61, $10.35, and $9.09, respectively, in quantities of 10,000. Click here for the CS5368/66/64 data sheets.

Cirrus Logic , 1-800-625-4084,

This product is truly unique since there are currently no other eight-channel audio A/D converters out there, according to Carl Alberty, senior manager of Cirrus' Mixed Signal Audio Division.

If you look at audio converters historically, there are plenty of multichannel D/A converters in the market, which is primarily driven by the fact that DVDs have exploded over the past five years, Alberty said. However, the need for integrated multichannel A/D converters has been a lot lower. “We've been serving this market with discrete two-channel A/D converters. Basically, the industry was off developing multichannel D/A converters because demand was a lot higher for high-performance multichannel playback systems. All that content had to be recorded and mastered to a digital medium though,” Alberty said.

There are two competing standards that are trying to replace the CDs as the mainstream medium for music playback — DVD Audio and Super Audio CD .

Since there are two competing high-resolution formats, and there is no real standard for copy protection agreed upon in the record industry, manufacturers have to convert copy protected multichannel digital content into analog before it leaves the box, Alberty said. “This is where multichannel A/D converters come in. Home theatre equipment, such as audio-video receivers and surround sound pre-amplifiers, support discrete six or eight-channel analog inputs, and the CS5366 and CS5368 are the only single chip IC's currently available to support this consumer audio market need,” he said.

There are some two- and four-channel lower performance devices available in the market — but they target different applications, Alberty said.

Click here to see a recently released dual-channel audio A/D converter by AKM Semiconductor.

Four years ago, Cirrus introduced the first new product from its A/D converter offering in quite some time. “We took the core of our two-channel CS5361 and we did five derivative products ranging from the 101 dB CS5340 to our flagship 120 dB CS5381, representing a complete refresh of that product line,” Alberty said.

This device is suited for space constrained applications. Not only does it pack eight channels of data conversion in a single chip, but it supports TDM, which is able to output eight channels on a single digital output. This is especially important in automotive applications since routing multiple digital outputs around the board can cause EMI issues, Alberty said.

Another key feature of these A/D converters is their low latency or group delay. “We use low delay digital filtering techniques. Signal delay is critical when you are doing live recordings and sound reinforcement. The delay through the CS5368 at 48 kHz sampling rates is a mere 0.25 ms, which is about 75 percent lower than competing devices,” Alberty said.

The CS5368 combines the functionality and performance of four CS5361s in a single package and it includes an on-chip oscillator. This adds a big degree of flexibility for the designer who doesn’t want to route high-speed master clocks around the board because of performance or EMI issues. “We also have overflow detection on each channel that can trigger an interrupt when the A/D converter inputs are being overdriven,” Alberty said.

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