原标题：AKM AK4679集成音频DSP的24位立体声CODEC解决方案

　　akm公司的AK4679是一款内置麦克风放大器、接收放大器、D类扬声器放大器、耳机放大器、线性放大器的24位立体声编解码音频DSP芯片。本文详细介绍了AK4679的主要特性、框图、应用框图以及采用AK4679芯片设计的评估开发板，通过评估板详细介绍了AK4679芯片各种模式下的应用设置及测试，评估板主要有评估板框图、电路原理图。

　　The AK4679 is a 24bit stereo CODEC and a built-in Microphone-Amplifier,Receiver-Amplifier, Mono Class-D Speaker-Amplifier, Cap-less Class-G Headphone-Amplifier and Line-Amplifier as well as HF/Audio DSP. The AK4679 features AKM DSP core to deal with hands free function for wide band and dual PCM I/F in addition to audio I/F that allows easy interfacing in mobile phone designs with Bluetooth I/F. The playback features also include 5-band Parametric EQ and Dynamic Range Control; therefore the AK4679 can automatically adjust the volume to a comfortable level that has no distortion and provides great flexibility. The AK4679 is available in a 78pin BGA, tilizing less board space than competitive offerings.

　　AK4679主要特性

　　 CODEC&Amp block

　　1. Recording Function (Stereo CODEC)

　　• 4 Stereo Input Selectors

　　• 4 Stereo Inputs (Single-ended) or 3 Mono Input (Full-differential)

　　• MIC Amplifier: +24dB ~ −6dB, 3dB step

　　• 2 Output MIC Power Supplies

　　• Digital ALC (Automatic Level Control): +36dB ~ −54dB, 0.375dB Step, Mute

　　• ADC CHARACTERISTICS: S/(N+D): 80dB, DR, S/N: 87dB (MIC-Amp=+18dB)S/(N+D): 80dB, DR, S/N: 92dB (MIC-Amp=0dB)

　　• Stereo Digital MIC Interface

　　• Wind-noise Reduction Filter

　　• Stereo Separation Emphasis

　　• 3-band Programmable Notch Filter

　　• Audio Interface Format: 24/16bit MSB justified, 24/16bit I2S, 16bit DSP Mode

　　2. Playback Function (Stereo CODEC)

　　• Digital Volume (+6dB ~ −57.0dB, 0.5dB Step, Mute)

　　• Digital ALC (Automatic Level Control): +36dB ~ −54dB, 0.375dB Step, Mute

　　• Stereo Separation Emphasis

　　• Dynamic Range Control

　　• 5-band Parametric Equalizer

　　• Stereo Line Output (Selectable Full-differential / Single-ended)

　　• Mono Receiver-Amp

　　- BTL Output

　　- Output Power: 60mW @ 32Ω

　　- Analog Volume: +12 ~ −30dB & Mute, 3dB Step

　　• Cap-less Stereo Class-G Headphone-Amp

　　- Output Power: 25mW @ 32Ω, 45mW @ 16Ω

　　- Analog Volume: +6 ~ −62dB & Mute, 2dB Step

　　- Zero crossing Detection

　　- Pop Noise Free at Power-ON/OFF

　　• Mono Class-D Speaker-Amp

　　- BTL Output

　　- Short Protection Circuit

　　- Output Power: 1.1W @ 8Ω, SVDD=4.2V, THD+N = 10% 0.89W @ 8Ω, SVDD=4.2V, THD+N = 1%

　　- Analog Volume: +12 ~ −30dB & Mute, 3dB Step

　　- Pop Noise Free at Power-ON/OFF

　　• Audio Interface Format:

　　- 24/16bit MSB justified, 16bit LSB justified, 16/24bit I2S, 16bit DSP Mode

　　3. Dual PCM I/F for Baseband & Bluetooth Interface

　　• Four sample Rate Converters (Up sample: up to x6: Down sample: down to x1/6)

　　• Sample Rate:

　　- PORTA (Mono): 8 ~ 16kHz

　　- PORTB (Stereo): 8 ~ 48kHz

　　• Digital Volume

　　• Slave Mode

　　• Audio Interface Format:

　　- 16bit Linear, 8bit A-law, 8bit μ-law

　　- Short/Long Frame, I2S, MSB justified

　　4. Power Management

　　5. Master Clock(Audio I/F):

　　(1) PLL Mode

　　• Frequencies: 11.2896MHz, 12MHz, 12.288MHz, 13MHz, 13.5MHz, 19.2MHz,

　　24MHz, 25MHz, 26MHz, 27MHz (MCKI pin)

　　32fs or 64fs (BICK pin)

　　(2) External Clock Mode

　　• Frequencies: 256fs, 512fs or 1024fs (MCKI pin)

　　6. Output Master Clock Frequencies(Audio I/F): 32fs/64fs/128fs/256fs

　　7. Sampling Frequency (Audio I/F)

　　• PLL Slave Mode (BICK pin): 8kHz ~ 48kHz

　　• PLL Master Mode:

　　8kHz, 11.025kHz, 12kHz, 16kHz, 22.05kHz, 24kHz, 32kHz, 44.1kHz, 48kHz

　　• EXT Master/Slave Mode:

　　8kHz ∼ 48kHz (256fs), 8kHz ~ 24kHz (512fs), 8kHz ~ 12kHz (1024fs)

　　8. Audio I/F: Master/Slave mode

　　DSP block

　　9. Embedded DSP

　　- Flexible programming with built-in program and data memories

　　- Hardware accelerator

　　- Word length: 24bit (Data RAM 24bit floating point)

　　- Multiplier 20 x 20 40bit (double precision available)

　　- Divider 20 / 20 20bit

　　- ALU: 44bit arithmetic operation (with overflow margin 4bit)

　　24bit floating point arithmetic and logic operation

　　- Program RAM: 4096w x 36bit

　　- Coefficient RAM: 2048w x 20bit

　　- Data RAM: 2048w x 24bit (24bit floating point)

　　- Offset Register: 32w x 15bit

　　- Delay RAM: 16384w x 24bit (24bit floating point)

　　- 5625 steps at fs16KHz, 1875 steps at fs48KHz

　　- Internal clock generator

　　10. DSP Serial Audio Interface Format

　　- 24bit Left justified, I2S,

　　- 16/24 bit linear, 8bit A-law, 8bit μ-law PCM

　　- Sampling rate 8 KHz ~ 48 KHz

　　- Up/Down sampling rate converter for Port#2 (8KHz → 16KHz)

　　11. Operational, sleep, suspend mode

　　General

　　12. μP I/F: I2C Bus (Ver 1.0, 400kHz Fast Mode), SPI (DSP block only)

　　13. Ta = −30 ~ 85°C

　　14. Power Supply:

　　• SVDD (SPK/RCV/LINE-Amp): 3.0 ~ 5.5V

　　• AVDD (Analog): 1.7 ~ 2.0V

　　• DVDD (Digital Core): 1.7 ~ 2.0V

　　• PVDD (HP-Amp & Charge Pump): 1.7 ~ 2.0V

　　• TVDDA, TVDDE (Digital I/F): 1.6 ~ 3.6V

　　• VDDE (DSP Core) 1.1 ~ 1.3V

　　15. Package : 78pin FBGA(4.5 x 4.5 mm, 0.4mm pitch)

　　图1.模拟框图

　　图2.数字框图

　　图3.DSP框图

　　采用AK4679评估板参考设计

　　The AKD4679-A is an evaluation board for AK4679, 24bit stereo CODEC with Microphone/ Receiver/Headphone/ Speaker/ Line amplifier as well as HF/Audio DSP. The AKD4679-A has the one Digital Audio I/F and two PCM I/F. It can achieve the interface with digital audio systems via optical connector and 10pin Port connector.

　　AK4679评估板参考设计的主要特性

　　DIR/DIT with optical input/output

　　10pin Header for Digital Audio I/F and PCM I/F (Baseband, Bluetooth)

　　BNC connector for an external clock input

　　10pin Header for I2C control mode

　　图4.参考设计框图