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Class D audio IC eases flat-panel DTV design

Posted: 11 Dec 2006 ?? ?Print Version ?Bookmark and Share

Keywords:DSP? ADC? Class D audio? digital TV? Cirrus Logic?

Class D audio IC from Cirrus Logic

Integrating a stereo ADC, sample-rate converter, digital audio processor and a 30W Class D stage that includes a PWM controller with drivers 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 TV 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 IC," said Jason Rhode, VP and general manager for the Mixed-Signal Audio Division.

The chip, which the company calls a "digital TV amplifier with ADC," is apart from the more recent Class-D product entries that, in the main, serve basic low-power analog consumer and car audio applications. Working from a stereo analog or (digital) PWM input, the CS4525 delivers up to 15W 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 24bit delta sigma architecture to secure its 100dB 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 15W per channel output, the IC can support so-called 2.1-channel configurations (2-by-7.5W per channel into 4-ohm half-bridge plus 1-by-15W into 8-ohm full bridge) as well a "low-frequency effects" configuration (1-by-30W 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.

The CS4525, in a 48-pin QFN package, is priced at $2.81 each in quantities of 10,000.

- Vince Biancomano

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