STSTA381BW Flat Panel TV 2.1 Channel Digital Audio System Solution

ST’s STA381BW is a 2.1-channel high-efficiency digital audio system with embedded digital audio processing, digital amplification, FFXTM power output stage, headphone and 2Vrms line output, providing all digital audio streams from source to speaker, cost-effective, low Power consumption and enhanced sound effects. STA381BW operating voltage from 4.5V to 26V, maximum to 30V, I2C control and I2S interface, sampling rate 32kHz-192kHz, with multiple protection functions such as short circuit, thermal, overcurrent and undervoltage protection , 1Vrms stereo analog output, three output power stage configurations, can drive 2x20W 8 ohm load or 2x9W 4 ohm + 1x20W 8 ohm load, mainly used in thin and light flat-screen TVs and home entertainment systems. This article introduces the main features and block diagram of STA381BW, digital Signal processing path block diagram and various application circuits.

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) in to 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 main features:

■ 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
STSTA381BW Flat Panel TV 2.1 Channel Digital Audio System Solution
Figure 1. STA381BW block diagram
STSTA381BW Flat Panel TV 2.1 Channel Digital Audio System Solution
Figure 2. STA381BW Processing Path, Part 1
STSTA381BW Flat Panel TV 2.1 Channel Digital Audio System Solution
Figure 3. STA381BW Processing Path, Part II: 2.1 Output, Individually Configurable

STSTA381BW Flat Panel TV 2.1 Channel Digital Audio System Solution
Figure 4. STA381BW Processing Path, Part II: 2.0 Output with B2DRC
STSTA381BW Flat Panel TV 2.1 Channel Digital Audio System Solution
Figure 5. STA381BW Processing Path, Part II: 2.1 Output Configuration and STCompressorTM
STSTA381BW Flat Panel TV 2.1 Channel Digital Audio System Solution
Figure 6. STCompressorTM block diagram
STSTA381BW Flat Panel TV 2.1 Channel Digital Audio System Solution
Figure 7. STA381BW External Audio Source to Line/Headphone Output Application Circuit
STSTA381BW Flat Panel TV 2.1 Channel Digital Audio System Solution
Figure 8. STA381BW F3X (from SAI) source to line/headphone output application circuit
STSTA381BW Flat Panel TV 2.1 Channel Digital Audio System Solution
Figure 9. STA381BW F3X auxiliary analog output circuit

Figure 10. Output Configuration Circuit for STA381BW Stereo Mode
For details, see:
http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/DM00029401.pdf

The Links:   NL6448BC20-20D CM35MXB2-24A

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