原标题：On Semi Rhythm SB3231 BTE 1.0助听器参考设计

　　On Semi公司的Rhythm SB3231是可配置的DSP系统,具有四路自适应反馈抵消的压缩电路,自适应降噪和FrontWave®静态方向性,I2C和SDA编程,模拟或数字音量控制,高质量200位音频处理和高保真CODEC,大功率/高增益功能,16 kHz或8 kHz带宽.本文介绍了Rhythm™ SB3231主要特性,框图,测试电路图, 典型可编程和调整应用电路图,以及BTE 1.0助听器参考设计主要特性和主要指标,BTE助听器电路框图和主要元件图.

　　Rhythm™ SB3231 is a trimmer-configurable DSP system based on a four-channel compression circuit featuring Adaptive Feedback Cancellation, Adaptive Noise Reduction, and FrontWave® static directionality.

　　Based on a phase cancellation method, Rhythm SB3231’s adaptive feedback reduction algorithm provides added stable gain to enable extra gain and user comfort. It features rapid adjustment for dynamic feedback situations and resistance to tonal inputs. The FrontWave directional system utilizes a pair of microphones to create a fully customizable static polar pattern, such as bidirectional, cardiod, hyper-cardiod and super-cardiod.

　　In addition to these adaptive algorithms, Rhythm SB3231 also supports the following features: up to four channel WDRC, low-distortion compression limiting, cross fading between audio paths for click-free memory changes, eight-band graphic equalizer, eight configurable generic biquad filters, programming speed enhancements, in-channel squelch to attenuate microphone and circuit noise in quiet environments, optional peak clipping, flexible compression adjustments, volume control, rocker switch, noise generation for tinnitus treatment, and industry leading security features to avoid cloning and software piracy.

　　Software Support

　　ARK is a set of software building blocks that can help reduce the time it takes to develop hearing aid fitting software. ARKonline® is an efficient web-based tool for creating product libraries and keeping them organized.

　　Rhythm™ SB3231主要特性:

　　FrontWave Directionality

　　Adaptive noise reduction

　　Adaptive feedback cancellation

　　WDRC compression with choice of 1, 2 or 4 channels of compression

　　Auto telecoil with programmable delay

　　EVOKE Lite™ acoustic indicators

　　Noise generator for tinnitus treatment or in-situ audiometry

　　Frequency response shaping with graphic EQ

　　Trimmer compatibility - four three-terminal trimmers with configurable assignments of control parameters

　　I²C and SDA programming

　　Rocker switch support for memory change and/or volume control adjustment

　　Analog or digital volume control with programmable range

　　High quality 20-bit audio processing

　　High power/high gain capability

　　SOUNDFIT® fitting software

　　Configurable low battery indicator

　　8 biquadratic filters

　　16 kHz or 8 kHz bandwidth

　　4 fully configurable memories with audible memory change indicator

　　96 dB input dynamic range with HRX™ Headroom Extension

　　128-bit fingerprint security system and other security features to protect against device cloning and software piracy

　　High fidelity audio CODEC

　　Soft acoustic fade between memory changes

　　Drives zero-bias two-terminal receivers

　　E1 RoHS compliant hybrid

　　图1. Rhythm SB3231框图

　　图2. Rhythm SB3231测试电路图

　　图3. Rhythm SB3231典型可编程应用电路图

　　图4. Rhythm SB3231典型调整应用电路图

　　BTE 1.0助听器参考设计

　　The BTE 1.0 Reference Design is a hardware reference design for a Behind-The-Ear (BTE) hearing aid using the Rhythm SB3231 preconfigured DSP system. It contains a single SB3231 device which enables implementation of a complete digital hearing aid with state-of-the-art features and specifications.

　　This reference design assumes that the BTE will be assembled using point-to-point wiring of the components.

　　Therefore, no description of a PCB design is given. A flex PCB implementation is a preferred component interconnect method for large production volumes, but is beyond the scope of this document.

　　The SB3231 design is supported by an extensive collection of design tools and documentation. This also details how ON Semiconductor ARK tools are used for the design and configuration of a new hearing aid.

　　The following steps outline the basic procedure used in this document for the design and assembly of a hearing aid:

　　1. Specify the requirements of the product which include the desired features and performance

　　2. Identify the components that will meet the requirements of the design

　　3. Create the mechanical drawings, schematics, and bill of materials for the design

　　4. Build a prototype model using the selected components

　　5. Model the acoustic performance of the device to determine the overall acoustic response

　　6. Program the device with the desired configuration

　　7. Calibrate the final assembly

　　8. Regulatory requirements for hearing instruments vary by country and region. Once the device has been assembled and tested, it will be necessary to submit the device for regulatory testing and approval before it can be sold as a hearing instrument.

　　图5. BTE 1.0助听器参考设计元件装配图

　　图6. BTE助听器元件图

　　图7. BTE 1.0助听器参考设计主要元件图

　　BTE 1.0助听器参考设计主要特性:

　　• Programmable BTE instrument with four channels of WDRC compression

　　• 96 dB input dynamic range

　　• Compatible with SOUNDFIT_ fitting software

　　• Adaptive feedback cancellation

　　• Programmable crossover frequencies

　　• 4 hearing programs

　　• Adaptive noise reduction using dual microphones

　　• Noise generator for tinnitus masking

　　• Auto telecoil with programmable delay

　　• Programmable Volume control (VC)

　　• Pushbutton memory select

　　• Power−on Delay

　　• Battery compartment

　　• Ear hook

　　• Disposable battery: Size 13

　　• Programmable acoustic tone for low battery voltage

　　• Housing available in different colors

　　• RoHS compliant

　　BTE 1.0助听器参考设计主要指标:

　　图8.BTE助听器电路框图