ST 公司的STA370BWS是 2.1路40W高效率數字音頻系統,是數字音頻處理,數字放大器控制和功率輸出級的整體解決方案, 2.1路提供兩個半橋和單個全橋, 提供2 x 9 W + 1 x 20 W輸出功率,兩個全橋的兩路可提供2x20W輸出功率,工作電壓7.0 V 到21.5 V,主要用于各種消費類電子,包括最新超薄的LED背光TV.本文介紹STA370BWS主要特性, 應用電路和輸出低通濾波器電路.
STA370BWS: 2.1-channel 40-W high-efficiency digital audio system Sound Terminal™ The STA370BWS is an integrated solution of digital audio processing, digital amplifier controls and power output stage to create a high-power single-chip FFX digital amplifier with high-quality and high-efficiency. Three channels of FFX processing are provided. The FFX processor implements the ternary, binary and binary differential processing capabilities of the full FFX processor.
The STA370BWS is part of the Sound Terminal. family that provides full digital audio streaming to the speakers and offers cost effectiveness, low power dissipation and sound enrichment.
The power section consists of four independent half-bridges. These can be configured via
digital control to operate in different modes.
2.1 channels can be provided by two half-bridges and a single full-bridge, supplying up to 2 x 9 W + 1 x 20 W of output power.
Two channels can be provided by two full-bridges, supplying up to 2 x 20 W of output power.
The IC can also be configured as 2.1 channels with 2 x 20 W supplied by the device plus a drive for an external FFX power amplifier, such as STA533WF or STA515W.
The STA370BWS flexibility is shown by the load driving capability of 11 W into 6 ohm and 20 W into 4 ohm with ternary modulation with a supply of 14 V.
Also provided in the STA370BWS are a full assortment of digital processing features. This includes up to 8 programmable biquads (EQ) per channel. Special digital signal processing techniques are available to manage low-frequency quantization noise in filters with very low cut-off frequencies. The coefficient range -4 to +4 allows easy high-shelf filter usage and better sound shaping. Available presets enable a time-to-market advantage by substantially reducing the amount of software development needed for functions such as audio preset volume loudness, preset volume curves and preset EQ settings. There are also new advanced AM radio interference reduction modes. Dual-band DRC dynamically equalizes the system to provide linear frequency speaker response regardless of output power level.
This feature separates the audio frequency band into two sub-bands independently processed to provide better sound clarity and to avoid speaker saturation.
The serial audio data input interface accepts all possible formats, including the popular I2S format. The high-quality conversion from PCM audio to FFX PWM switching provides over 100 dB of SNR and of dynamic range.
Full short-circuit protection is also embedded protecting output to GND, output to VCC and output to output connections. The short-circuit (fault) condition is checked at device turn-on, so if a short circuit is detected the IC does not power up. This avoids dangerous conditions, component break down and minimizes the return from the field.
The new F3X. modulation, already offered within STA369BWS, is capable of digitally filtering the PWM carrier to simplify external filtering requirements, AM interference and EMI. F3X. is implemented in the auxiliary output of STA370BWS and it is specifically designed for application where a simple op-amp can be used to drive an auxiliary headphone line.
STA370BWS主要特性:
Wide-range supply voltage, 7.0 V to 21.5 V
Three power output configurations:
– 2 channels of ternary PWM (2 x 20 W into 8 ohm at 18 V) + PWM output
– 2 channels of ternary PWM (2 x 20 W into 8 ohm at 18 V) + ternary stereo line-out
– 2.1 channels of binary PWM (left, right, LFE) (2 x 9 W into 4 ohm + 1 x 20 W into 8 ohm at 18 V)
Load-driving capabilities:
– 11 W into 6 ohm at 14 V, ternary
– 20 W into 4 ohm at 14 V, ternary
FFX with 100-dB SNR and dynamic range
Scalable FFX modulation index (up to 100%)
Selectable 32- to 192-kHz input sample rates
I2C control with selectable device address
Digital gain/attenuation +48 dB to -80 dB with step resolution:
– 0.125 dB/step from -60 dB to +48 dB
– 0.25 dB/step from -80 dB to -60 dB
Soft volume update with programmable ratio
Individual channel and master gain/attenuation and soft/hard mute.
Two independent DRCs configurable as a dual-band anti-clipper (B2DRC) or as
independent limiters/compressors with optional global DRC capability
EQ-DRC for DRC based on filtered signals
Dedicated LFE processing for bass boosting with 0.125-dB/step resolution
Audio presets:
15 preset crossover filters
5 preset anti-clipping modes
Preset night-time listening mode
I2S input data interface
Input and output channel mapping
Programmable zero-detect mute
Automatic invalid input-detect mute
Up to 8 user-programmable biquads/channel
Three coefficients banks for EQ presets storing with fast recall via I2C interface
Extended filter dynamics +4/-4 for better sound shaping and easier filter implementation
Bass/treble tones and de-emphasis control
Selectable high-pass filter for DC blocking
Advanced AM interference frequency switching and noise suppression modes
F3X™ advanced PWM modulation scheme for carrier suppression (headphone or line output)
Selectable high- or low-bandwidth noise-shaping topologies
96-kHz internal processing sample rate with quantization error noise shaping for very low cut-off frequency filters
Full short-circuit protection at device power-up
Coefficient checksum with software reset capabilities
圖1.STA370BWS應用電路
圖2.STA370BWS輸出低通濾波器
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