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Sound Terminal 2.1-channel high-efficiency digital audio system

The STA381BW is an integrated solution embedding digital audio processing, digital amplification, FFXTMpower 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, proprietary technology from STMicroelectronics. FFXTMis 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 FFXTMprocessor.

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 can also be driven through the PWM output. The STA381BW is able to deliver 2 x 20 W (ternary) into an 8 Ω load at 18 V or 2 x 9 W (binary) into a 4 Ω load, plus 1 x 20 W (ternary) into an 8 Ω 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 Ω 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-of-the-art multi-band DRC, STCompressorTMequalizes the system to provide active speaker protection with full audio quality preservation against sudden sound peaks. Moreover, STSpeakerSafeTMtechnology offers reliable speaker protection under any condition. The master clock can be from stable BICKI (64xfs, 50% duty cycle) or external XTI.

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Key Features

  • Wide-range supply voltage
  • 4.5 V to 26 V (operating range)
  • 30 V (absolute maximum rating)
  • I2C control with selectable device address
  • Embedded full IC protection
  • 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 8 Ω ternary modulation
  • 2 x 9 W into 4 Ω + 1 x 20 W into 8 Ω
  • FFXTM100 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
  • New F3XTManalog output
  • New fully programmable noise-gating function
  • Headphone
  • Embedded negative charge pump
  • Full capless output configuration
  • Driving load capabilities: 40 mW into 32 Ω
  • 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
  • STSpeakerSafeTMprotection circuitry
  • Pre- and post-processing DC blocking filters
  • Checksum engine for filter coefficients
  • PWM fault self-diagnosis
  • STCompressorTMdual-band DRC

Design Resources


Technical Documentation

Product Specifications

Description Version Size
DS7227: Sound Terminal® 2.1-channel high-efficiency digital audio system
8.0 6,302 KB

Application Notes

Description Version Size
AN3340: Loudspeaker characterization and compensation
1.3 3,944 KB
AN3959: 2.0-channel demonstration board based on the STA381BW and STA381BWS
3.0 4,312 KB
AN3984: IIR filter design equations for Sound Terminal® devices
1.1 494 KB
AN4118: APWLink USB interface board for Sound Terminal® demonstration boards
2.0 1,029 KB

User Manual

Description Version Size
UM1545: Using the Audio Processor Workbench (APWorkbench)
1.0 3,221 KB

Presentations & Training Material

Training Material

Description Version Size
Learn the basics about STSpeakerSafe technology
1.0 197 KB

Publications and Collaterals


Description Version Size
APWorkbench software for audio ICs and MEMS microphones
2,349 KB


Description Version Size
Analog audio solution
1.0 1,371 KB
FFX - Full flexible amplification
4,722 KB

Sample & Buy

Part Number Marketing StatusPackagePacking TypeOperating Temperature (min) Operating Temperature (max) Automotive GradeOrder From STUnit Price (US$)*
Distributor AvailabilityRoHS Compliance GradeDownload
Material Declaration**
STA381BWTRNRNDVFQFPN 48 7X7X0.9Tape And Reel0150_-1Distributor reported inventory date: 2015-10-02
Distributor NameRegionStockMin. order

(*) Suggested Resale Price per unit (USD) for BUDGETARY USE ONLY. For quotes, prices in local currency, please contact your local ST Sales Office or our Distributors
(**) The Material Declaration forms available on may be generic documents based on the most commonly used package within a package family. For this reason, they may not be 100% accurate for a specific device. Please contact our sales support for information on specific devices.
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