AKM公司的AK4687是具有两路输入选择器和线路驱动器的异步立体声CODEC,ADC/DAC接口能接纳高达24位输入数据,并支持异步操作.24位立体声ADC采用64x过取样,取样频率高达48kHz,线性相位数字抗混淆滤波器,S/(N+D)为83dB,动态范围99dB,而24位立体声DAC采用128x过取样,取样频率高达192kHz,24位8倍数字滤波器,S/(N+D)为95dB,动态范围105dB.主要用在蓝光影碟机, 家庭影院,DTV,数字录音系统.本文介绍了AK4687主要特性, 方框图,典型应用电路图,以及评估板AKD4687-A功能,方框图和电路图与元件布局图.
The AK4687 is a stereo audio CODEC with 2-channel input selector and a line driver. The interfaces of ADC/DAC can accept up to 24bit input data and support asynchronous operation. The input range of the pre-amplifier, that supports 3ch stereo inputs, is selectable by external resistors. Both the input stereo selector and output drivers support ground reference 2Vrms In/Output, making it possible to remove AC-coupling capacitors and reducing external parts. The AK4687 has a dynamic range of 99dB for ADC, 105dB for DAC. It is well suitable for digital recording systems, digital TVs, Blu-ray recorders and Home theater systems.

AK4687主要特性:
􀂆 Asynchronous ADC/DAC Operation
􀂆 3:1 Capless Stereo Line Input Selector
􀂆 24bit Stereo ADC
- 64x Oversampling
- Sampling Rate up to 48kHz
- Linear Phase Digital Anti-Alias Filter
- S/(N+D): 83dB
- Dynamic Range, S/N: 99dB
- Digital HPF for Offset Cancellation
􀂆 24bit Two Stereo DAC
- 128x Oversampling
- Sampling Rate up to 192kHz
- 24bit 8 times Digital Filter
- S/(N+D): 95dB
- Dynamic Range, S/N: 105dB
- De-emphasis Filter
􀂆 High Jitter Tolerance
􀂆 External Master Clock Input:
256fs, 384fs, 512fs 768fs (fs=32kHz ∼ 48kHz)
128fs, 192fs, 256fs 384fs (fs=64kHz ∼ 96kHz)
128fs, 192fs (fs=128kHz ~ 192kHz)
􀂆 2 Audio Serial I/F (PORT1, PORT2)
- Master/Slave mode (PORT1)
- I/F format
PORT2: MSB, LSB justified (16/24 bit), I2S
PORT1: MSB, LSB justified (16/24 bit), I2S
􀂆 Hardware / I2C-bus Control
􀂆 Operating Voltage:
- Digital I/O and Charge Pump: 3.0V ∼ 3.6V
- ADC Analog: 3.0V ∼ 3.6V
- DAC Analog: 3.0V ∼ 3.6V
􀂆 Package: 48pinLQFP

图1.AK4687方框图

图2.AK4687典型连接图(I2C控制模式, CAD0引脚= “L”,主模式)

图3.AK4687典型连接图(H/W控制模式, MCLK=768fs,主模式)

评估板AKD4687-A
AKD4687-A is an evaluation board for AK4687, which is a single chip 24bit CODEC with a 2ch ADC and a 2ch DAC. It is possible to evaluate not only A/D and D/A of the AK4687, but also asynchronous operation characteristics. Also, the board could be connected to a digital’s audio equipment easily with S/PDIF connectors.

评估板AKD4687-A功能:
􀂆 Compatible with 2 types of digital audio interface
- BNC (S/PDIF) input/output with DIT/DIR (AK4118A)
- 10pin headers for interfacing with external data source
􀂆 Separate power supply or regulator power supply
􀂆 10pin header for register control

图4.评估板AKD4687方框图

图5.评估板AKD4687略图

图6.评估板AKD4687电路图(1)

图7.评估板AKD4687电路图(2)

图8.评估板AKD4687电路图(3)

图9.评估板AKD4687电路图(4)

图10.评估板AKD4687电路图(5)

图11.评估板AKD4687电路图(6)

图12.评估板AKD4687元件布局图