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Audio ICs promise heightened HDTV experience

Posted: 05 Oct 2007 ?? ?Print Version ?Bookmark and Share

Keywords:audio processor? Class-D power amplifier? advanced TV systems?

Analog Devices Inc.'s latest audio processors and Class-D audio power amplifiers, which are part of the company's Advantiv lineup, deliver a complete advanced TV audio subsystem while allowing designers to meet multiple product performance and price targets. Designed to work together, the chips provide all the critical subsystem functionality, including an embedded processing engine to ensure big sound from small speakers; analog interfaces for line I/Os; analog broadcast audio decoding and speaker output; flexible, multiformat digital interfaces for HDMI sources and all digital terrestrial and satellite broadcasts); and A/V 'lip-synch' delay correction and synchronization.

According to Martin Cotter, product line director, Advanced Television Segment, Analog Devices, "The engineering required for the audio processor and Class-D power stage amplifier to work well together is significant. ADI has solved the design difficulties associated with this open-loop interface, thereby eliminating customary system-level concerns, such as "pop/click" reduction and physical interfacing challenges. This reduces design cycle time, minimizes system cost, and delivers a quality audio experience for consumers--key benefits for TV manufacturers with defined 12-month new product refresh cycles."

Powerful processing
The ADAV4101, ADAV4312 and ADAV4322 audio processors incorporate a powerful, embedded processing engine to compensate for the space-constrained speakers in today's thin flat, LCD, and plasma TV designs. This "digital audio enhancement engine" does all the processing necessary to deliver the big sound required to match HD video quality. This feature is coupled with high-performance, multichannel, 24bit ADCs and DACs that accept analog line inputs from DVD/VCR players and set-top boxes and drive analog audio to power amplifiers for speakers or auxiliary outputs.

"The ADAV43x2 and ADAV44x2 audio processors are not just I/O devices with lots of high performing digital interfaces, analog interfaces and multiple ADCs and DACs doing advanced signal processing," said Cotter. "They are enhanced, fully programmable audio processors, with full support for HD-ready and iDTV designs. They also support multistandard analog broadcasts, such as BTSC, EIAJ, A2-Korea, A2-Europe, and NICAM, from analog terrestrial tuners via an on-chip demodulator and decoder."

The audio processors provide a range of flexible digital interfaces, with sample rate conversion, which ensures the devices are fully compatible with the requirements of interfacing to HDMI audio and digital tuners. By default, the devices load a dedicated TV audio flow that incorporates full matrix switching to allow any input source type to be connected to any output.

While providing standard TV audio processing, they can also be designed to enable advanced audio features, such as full-room equalization, surround-sound virtualization or bass-frequency enhancement. Many of these features are offered from ADI or under license from third-party suppliers, such as Dolby, SRS-Labs, and BBE. The audio processors also enable design engineers to customize the audio flow to conform to specific system or customer needs. Analog Devices provides a range of tools, including the award winning SigmaStudio graphical design tool, to allow easy debug and verification of any customized implementations. They also feature automatic volume control to compensate for volume changes during advertisements or when switching channels, dynamic bass, a multi-band equalizer, and up to 400 ms of delay memory for audio/video synchronization.

Perfect complement
Meanwhile, ADI's audio processors are complemented by new Class-D amplifiers. The ADAU1590, ADAU1592 and ADAU1513 are 2-channel Class-D amplifiers. They have a 90 percent power efficiency rating at 8? and a 101dB dynamic range. The ADAU1590 and ADAU1592 feature on-chip pulse-density modulation (PDM) and a closed-loop architecture that ensures premium audio amplification by conditioning a signal to compensate for output errors before it is sent to the speaker. They also include integrated sigma-delta modulators that accept an analog input signal and generate a switching output to drive the speakers directly. The ADAU1590 and ADAU1592 achieve 0.005 percent total harmonic distortion-plus-noise (THD+N) while delivering 18W (stereo) and 11W (stereo) into 6?, respectively. The low distortion, noise and power supply rejection ratio (PSRR) combine with the optimized interface of ADI's audio processor (ADAV4101/4312/4322) to suppress audio pops and clicks when the TV is turned on or off and eliminate residual background noise when the speaker volume is at its lowest setting.

The ADAU1513 Class-D power stage, delivering 14W (stereo) into 8? with 90 percent efficiency, is directly driven from the PWM digital outputs on the ADAV4201, ADAV4412 or ADAV4422 audio processor. The power stage comprises thermal and output short-circuit protection with logic-level error flag outputs for interfacing to a system microcontroller along with reset and mute control of the power stage.

Available now
The ADAV4101, ADAV4312, ADAV4322, ADAV4201, ADAV4412 and ADAV4422 audio processors are now available in production volume. They are available in an 80-lead LQFP and are pin-for-pin and software-register compatible.

The ADAU1590, ADAU1592 and ADAU1513 Class-D amplifiers too, are available in production volume. The ADAU1590, ADAU1592 and ADAU1513 amplifiers come in 48-lead LFCSP and 48-lead TQFP.

- Dennis Barker
Digital TV Designline

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