Closed-loop Class-D power amp delivers improved sound, PSRR

Texas Instruments has announced the TAS5706 digital-input 20-W stereo Class-D speaker amplifier, offered as the industry's first such device using closed-loop feedback. The device's closed-loop architecture is said to offer improved sound quality through greater speaker control, a higher PSRR - allowing operation even directly from a backlight supply of an LCD TV - and greater EMC compared to open-loop parts.

According to the company, the part provides a more accurate sound and a lower audio subsystem cost in home entertainment applications such as HDTVs and media docking stations. Other features include on-chip dynamic range compression, a dedicated subwoofer channel for 2.1 applications, and speaker equalization.

Two serial data inputs allow processing of up to four discrete audio channels and seamless integration to most digital audio processors and MPEG decoders. A fully programmable data path allows these channels to be routed to the internal speaker drivers or output via the subwoofer or headphone PWM outputs.

The TAS5706 receives all clocks from external sources and operates at a 384-kHz switching rate for 32-, 48-, 96-, and 192-kHz data, and at a 352.8-kHz switching rate for 44.1-, 88.2-, and 176.4-kHz data. The 8-times oversampling combined with the fourth-order noise shaper are claimed to provide a flat noise floor and excellent dynamic range from 20 Hz to 20 kHz.

The device is designed to be easily programmed using the company's PurePath Studio Graphical Development Environment. For example, speaker EQ coefficients are automatically calculated by dragging points on speaker response curves.

The TAS5706 is available in a 10 x 10-mm QFP and priced at $5.46 in 100-piece quantities. An evaluation module, the TAS5706EVM, is also available.

Texas Instruments, 800-477-8924, www.ti.com

Product literature:
TAS5706 information page
TAS5706 datasheet (PDF)
Evaluation Module information page