原标题：AKM AK4957 24位立体声CODEC解决方案

　　akm公司的AK4957是集成了麦克风,扬声器,视频放大器和LDO的24位立体声CODEC,具有录音功能,播放功能和视频功能,主时钟有PLL和外接时钟两种模式,MIC放大器具有+21dB/+18dB/+16dB/+14dB/+8dB/0dB增益,数字自动音量控制(ALC),模拟电源(AVDD)2.8V-3.6V,数字电源(DVDD)1.6V-2.0V,适合于具有录音/播放功能的手提设备.本文介绍了AK4957主要特性,框图, 立体声和单声道数字MIC连接图,以及评估板AKD4957-B功能,框图,电路图和PCB布局图.

　　The AK4957 is a 24bit stereo CODEC with a microphone, speaker, video amplifiers and LDO. The input circuits include a microphone amplifier and the output circuits include a speaker amplifier. It is suitable for portable application with recording/playback function. A one channel composite In/Out video amplifier is also integrated. The AK4957 is available in a small 32pin QFN (4mm x 4mm, 0.4mm pitch), saving mounting area on the board.

　　AK4957主要特性:

　　1. Recording Functions

　　• Stereo Single-ended input with two Selectors

　　• MIC Amplifier (+21dB/+18dB/+16dB/+14dB/+8dB/0dB)

　　• Digital ALC (Automatic Level Control) (Setting Range: +36dB ∼ −54dB, 0.375dB Step)

　　• ADC Performance: S/(N+D): 83dB, DR, S/N: 88dB (MIC-Amp=+18dB)S/(N+D): 85dB, DR, S/N: 96dB (MIC-Amp=0dB)

　　• Microphone Sensitivity Compensation

　　• 5 Band Notch Filter

　　• Stereo Separation Emphasis Circuit

　　• Digital MIC Interface 2. Playback Functions

　　• Soft Mute

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

　　• Digital Volume Control (+12dB ~ −115dB, 0.5dB Step & Mute)

　　• Stereo Separation Emphasis Circuit

　　• Stereo Line Output

　　- Output Voltage: 1Vrms (AVDD= 3.3V)

　　- S/(N+D): 85dB

　　- S/N: 92dB

　　• Mono Mixing Output

　　• Mono Speaker-Amplifier

　　- S/(N+D): 65dB@150mW, 60dB@250mW,

　　- S/N: 90dB

　　- BTL Output

　　- Output Power: 400mW@8Ω (AVDD=3.3V)

　　• Analog Mixing: BEEP Input

　　3. Master Clock:

　　(1) PLL Mode

　　• Frequencies: 11.2896MHz, 12MHz, 13.5MHz, 24MHz, 27MHz (MCKI pin)32fs or 64fs (BICK pin)(2) External Clock Mode

　　• Frequencies: 256fs, 512fs or 1024fs (MCKI pin)Output Master Clock Frequency: 32fs/64fs/128fs/256fs

　　4. Sampling Frequencies

　　• PLL Slave Mode (MCKI pin):8kHz, 11.025kHz, 12kHz, 16kHz, 22.05kHz, 24kHz, 32kHz, 44.1kHz, 48kHz

　　• PLL Master Mode:8kHz, 11.025kHz, 12kHz, 16kHz, 22.05kHz, 24kHz, 32kHz, 44.1kHz, 48kHz

　　• EXT Master/Slave Mode:

　　7.35kHz ~ 48kHz (256fs), 7.35kHz ∼ 48kHz (512fs), 7.35kHz ∼ 13kHz (1024fs)

　　5. μP I/F: 3-wire Serial, I2C Bus (Ver 1.0, 400kHz Fast-Mode)

　　6. Master/Slave Mode

　　7. Audio Interface Format: MSB First, 2’s complement

　　• ADC: 24bit MSB justified, 16/24bit I2S

　　• DAC: 24bit MSB justified, 16bit LSB justified, 24bit LSB justified, 24bit I2S

　　8. Video Functions

　　• One Composite Signal Input

　　• Video Amplifier for Composite Signal Output Gain: +6 / +9 / +12 / +16.5dB

　　• Low Pass Filter

　　9. Ta = −30 ∼ 85℃

　　10. Power Supply:

　　• Analog Power Supply (AVDD): 2.8 ~ 3.6V

　　• Digital Power Supply (DVDD): 1.6 ~ 2.0V

　　• Digital I/O Power Supply (TVDD): 1.6 or DVDD – 0.2 ~ 3.6V

　　Package: 32pin QFN (4.0 x 4.0 mm, 0.4mm pitch)

　　图1. AK4957框图

　　图2. AK4957立体声数字MIC连接案例图

　　图3. AK4957单声道数字MIC连接案例图

　　图4. AK4957系统连接图

　　评估板AKD4957-B

　　The AKD4957-B is an evaluation board for AK4957, 24bit stereo CODEC with a microphone/ speaker/ video amplifiers, and LDO. The AKD4957-B can control various settings using the USB port, can be easily evaluated. Also features a USB Audio device, the audio signal can be input through the USB port from PC. The AKD4957-B has the Digital Audio I/F and can achieve the interface with digital audio systems via optical connector. AKD4957-B is equipped with Line output, Mic input and Headphone output terminals. Has also carried Flash ROM, a stand-alone operation is possible.

　　评估板AKD4957-B功能:

　　• DIR/DIT with optical input/output

　　• With USB-Audio device

　　• Equipped with three digital audio interface

　　- Optical Input / Output

　　- USB Input

　　- 10-pin header for external interfaces

　　• USB port for board control

　　图5.评估板AKD4957-B框图