ST公司的STA381BW是2.1通路高效數字音頻系統,嵌入了數字音頻處理,數字放大, FFXTM功率輸出級,耳機和2Vrms線路輸出,為從源到揚聲器提供了所有的數字音頻流,具有成本效益,低功耗和增強的聲效果. STA381BW的工作電壓從4.5V到26V,最大到30V,I2C控制和I2S接口,取樣速率32kHz-192kHz,具有多種保護功能如短路,熱,過流和欠壓保護,1Vrms立體聲模擬輸出,三種輸出功率級配置,可驅動2x20W8歐姆負載或2x9W 4歐姆+1x20W 8歐姆負載,主要用在輕薄型平板電視和家庭娛樂系統.本文介紹了STA381BW主要特性和方框圖,數字信號處理通路框圖以及多種應用電路.

The STA381BW is an integrated solution embedding digital audio processing, digital amplification, FFXTM power output stage, headphone and 2 Vrms line outputs. It is part of the Sound Terminal® family and provides full digital audio streaming from the source to the speaker, offering cost effectiveness, low power dissipation and sound enrichment.

The STA381BW input section consists of a flexible digital input serial audio interface, feeding the digital processing unit, and an analog 1 Vrms input for a seamless connection with pure analog sources. The serial audio data input interface supports many formats,including the popular IIS format.

The STA381BW is based on an FFXTM (Fully Flexible Amplification) processor, an STMicroelectronics proprietary technology. FFXTM is the evolution of the ST ternary technology: the advanced processor is available for ternary, binary, binary differential and phase shift PWM modulation.The STA381BW embeds the ternary, binary and binary differential implementations, a subset of the full capability of the FFXTM processor. The STA381BW power section consists of four independent half-bridges. These can be configured via digital control to operate in different modes. A 2.1 channel setup can be implemented with two half-bridges (L/R) together with a single full-bridge (subwoofer).Alternatively, the 2.0 channel setup can be done with two full-bridges. When using this configuration an external amplifier for the SW channel also can be driven through the PWM output. The STA381BW is able to deliver 2 x 20 W (ternary) into an 8 load at 18 V or 2 x 9 W (binary) into a 4 load, plus 1 x 20 W (ternary) into an 8 load at 18 V. The STA381BW also provides a capless headphone out (with embedded negative charge pump), able to deliver up to 40 mW into a 32 load or, alternatively, can be configured as a 2 Vrms line output.

The STA381BW digital processing unit includes up to 12 programmable biquads (EQs)allowing perfect sound equalization and offering advanced noise-shaping techniques.Moreover, the coefficient range ensures a great variety of filter shapes (low/high-pass,low/high shelf, peak, notch, band-pass). The equalization engine is fully compatible with the ST speaker compensation technology embedded into the APWorkbench suite. A state-ofthe-art multi-band DRC, STCompressorTM, equalizes the system to provide active speaker protection with full audio quality preservation against sudden sound peaks. Moreover, STSpeakerSafeTM technology offers reliable speaker protection under any condition. The master clock can be from stable BICKI (64xfs, 50% duty cycle) or external XTI.

STA381BW主要特性:

■ Wide-range supply voltage

– 4.5 V to 26 V (operating range)

– 30 V (absolute maximum rating)

■ I2C control with selectable device address

■ Full IC protection embedding:

– Manufacturing short-circuit protection (out vs. gnd, out vs. vcc, out vs. out) Thermal protection Overcurrent protection

– Undervoltage protection

■ 1 Vrms stereo analog input

■ I2S interface, sampling rate 32 kHz ~ 192 kHz, with internal sampling frequency converter for fixed processing frequency

■ Three output power stage configurations

– 2.0 mode, L/R full bridges

2.1 mode, L/R two half-bridges, subwoofer full bridge

– 2.1 mode, L/R full bridges, PWM output for external subwoofer amplifier

■ Driving load capabilities

– 2 x 20 W into 8ohm ?ternary modulation

– 2 x 9 W into 4 ohm?+ 1 x 20 W into 8 ohm

■ FFXTM 100 dB dynamic range

■ Fixed output PWM frequency at any input sampling frequency

■ Embedded RMS meter for measuring real-time loudness

■ Two analog outputs:

– Selectable headphone / line out driver with adjustable gain via external resistors

– Auxiliary F3XTM analog output for external driver

■ Headphone:

– Embedded negative charge pump

– Full capless output configuration

– Driving load capabilities: 40 mW into 32 ohm

■ Line out:

– 2 Vrms line output capability

■ Up to 12 user-programmable biquads with noise-shaping technology

■ Direct access to coefficients through I2C shadowing mechanism

■ Fixed (88.2 kHz / 96 kHz) internal processing sampling rate

■ Two independent DRCs configurable as a dual-band anticlipper or independent limiters/compressors (B2DRC)

■ Digital gain/att +48 dB to -80 dB with 0.125 dB/step resolution

■ Independent (fade in, fade out) soft volume update with programmable rate 48 ~ 1.5 dB/ms

■ Bass/treble tones control

■ Audio presets:15 crossover filters, 5 anticlipping modes, nighttime listening mode

■ STSpeakerSafeTM protection circuitry:

– Pre and post processing DC blocking filters

– Checksum engine for filter coefficients

– PWM fault self-diagnosis STCompressorTM dual-band DRC

圖1.STA381BW方框圖

圖2.STA381BW處理通路,第一部分

圖3.STA381BW處理通路,第二部分:2.1輸出,單獨可配置


圖4.STA381BW處理通路,第二部分:帶B2DRC的2.0輸出

圖5.STA381BW處理通路,第二部分:2.1輸出配置和STCompressorTM

圖6.STCompressorTM方框圖

圖7.STA381BW外接音頻源到線路/耳機輸出應用電路

圖8.STA381BW F3X(來自SAI)源到線路/耳機輸出應用電路

圖9.STA381BW F3X輔助模擬輸出電路

圖10.STA381BW立體聲模式的輸出配置電路
詳情請見:
http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/DM00029401.pdf