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Class D audio system tunes in for digital TV

Austin, Tex.&#8212Integrating a stereo analog-to-digital converter, sample-rate converter, digital audio processor and a 30-watt Class D amplifier that includes a PWM controller and power stage, Cirrus Logic touts its CS4525 as an innovative Class D audio IC that greatly simplifies system design for the global flat-panel digital television market.

“Because of its high level of integration, the CS4525 gives flat-panel DTV manufacturers a superior design solution for managing the audio signal chain, providing a wealth of features and exceptional audio output and quality in a simple-to-use integrated circuit,” said Jason Rhode, vice president and general manager for the Mixed-Signal Audio Division.

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The chip, which the company calls a “digital TV amplifier,” is apart from the more recent Class-D product entries (see Related Stories) that, in the main, serve basic low-power analog consumer and car audio applications. An ADC is integrated to support stereo analog audio sources in addition to standard PCM digital audio inputs. The CS4525 delivers up to 15 watts per channel into 8-ohm speakers. Thus it's among the more powerful entries for recent Class-D products for mid-power applications. In all other respects, its audio capabilities are on a par with top of the line devices for dynamic range, low distortion at both low and elevated power levels, and implementing suitable PWM modulator technology to eliminate radiated emissions (EMI).

The CS4525 uses a 24-bit delta sigma architecture to secure its 100 dB dynamic range. The chip's built-in sample-rate converter manages a variety of incoming audio signals for various applications (e.g., PCM stereo, audio from DVD, etc.) while also eliminating the effects of clock-jitter. The chip's spread-spectrum PWM modulator serves to reduce EMI.

The CS4525's on-board digital audio processor facilitates “speaker tuning,” i.e., parametric equalization, auxiliary output for lip-sync delay, and bass management. In addition to its typical full-bridge stereo configurations that provides 15 watts per channel output, the IC can support so-called 2.1-channel configurations (2-by-7.5 watts per channel into 4-ohms half-bridge plus 1-by-15 watts into 8-ohms full bridge) as well a “low-frequency effects” configuration (1-by-30 watts into 4 ohms, parallel full-bridge). Its power stage eliminates the need for a heat sink (additionally, the company makes available to OEMs a companion chip, the CS4412, a power-stage only IC). With special attention to power management that's especially important in slim, flat-panel TVs, the chip also incorporates proprietary thermal warning and foldback circuitry, which scales back output levels if the chip temperature rises excessively.

Click here for the product datasheet.
The CS4525, in a 48-pin QFN package, is priced at $2.81 each in quantities of 10,000.

Cirrus Logic , 1-800-888-5016,
www.cirrus.com

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