Closed-loop, digital-input class-D amplifier is a first says TI

26th February 2008

ES Admin

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Texas Instruments has introduced the industry’s first digital-input, 20W stereo Class-D speaker amplifier with closed loop feedback. Closed loop architectures produce a richer, more accurate sound and lower system cost by relaxing power supply performance requirements. Highly flexible output configurations along with intuitive support tools ease design and speed time to market for manufacturers of HDTVs, including LCD, plasma and DLP TVs, and media docking stations.

“Industrial design and increasingly smaller form factors are becoming standard in the HDTV market, placing increasing pressure on manufacturers,” said Art George, senior vice president of TI’s high-performance analog business unit. “TI is addressing these form factor challenges with innovative products like the TAS5706, which provides a cost-efficient solution that delivers high quality audio in slim designs.”

Improving audio performance, the closed loop architecture enables the audio subsystem to have greater control over the speaker, reproducing a tighter, more accurate sound, with improved bass response. In addition, the closed loop architecture provides superior power supply rejection ratio (PSRR), which reduces power supply noise coupling into the audio band. Better noise immunity allows engineers to design lower-cost power supplies. In fact, for LCD-TVs, a TAS5706 audio amp can be powered off the existing +24V backlight power supply, making a dedicated power rail for the audio subsystem unnecessary.

Other sound enhancements are made possible by the on-chip audio processing capabilities of the TAS5706, including dynamic range compression (DRC), a dedicated subwoofer channel for 2.1 applications, and speaker equalization (EQ). Speaker EQ adjusts the audio to compensate for low-quality speakers or for sub-optimal speaker placement and size in thin form factors.

Highly flexible platform and intuitive tools ease design and reduce development time

The TAS5706 provides flexible output configurations that allow manufacturers to use a single platform across multiple products. Stereo, quad and 2.1 output configurations are supported along with PWM headphone and subwoofer outputs.

In addition to versatile outputs, TI’s PurePathTM Studio Graphical Development Environment reduces development time and makes programming simple. For example, speaker EQ coefficients are automatically calculated by simply dragging points on the speaker response curves. Evaluation modules, application notes and other technical documents are available to facilitate rapid design cycles.