AKM公司的AK7757是一款内置4通道DAC、一个可选输入立体声ADC通道、一个单声道ADC和一个数字音频接口的数字音频信号处理器。该音频数字信号处理器具有在48kHz的采样速率下达到1536阶的并行算法操作性能。本文详细介绍了AK7757的主要特性、内部框图、内部DSP框图以及采用AK7757芯片设计的评估开发板，通过评估板详细介绍了AK7757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 AK7757 is a digital signal processor with an integrated 4ch DAC, a stereo ADC with input selector, a mono ADC and an integrated digital audio interface. The audio DSP has 1536 step/fs (at 48kHz sampling) parallel arithmetic operation performance. As the AK7757 is a RAM based DSP, it is programmable for user requirements to realize the audio effects process or the proprietary high-performance HF. It is housed in a 48pin LQFP which is a small package to save the PCB space.

AK7757主要特性
􀂆DSP
- Word length: 24bits (Data RAM: F24 floating point)
- Processing Speed: 13.6 ns (9216step/fs; fs = 8kHz)
- Multiplication: 20 x 20 → 36-bit Double precision arithmetic available
- Divider 20 / 20 → 20-bit
- ALU: 40-bit arithmetic operation (overflow margin 4bits) 24-bit floating point arithmetic and logic operation
- Program RAM: 4096 x 36bits
- Coefficient RAM: 4096 x 20bits
- Data RAM: 2048 x 24bits (F24 floating point)
- Delay RAM: 4096 x 20bits, 4096 x 20bits
- Master Clock: 73.7MHz
- JX pins (interrupt)
􀂆2ch ADC1
- Sampling Frequency: 8kHz~48kHz
- 3in / 1out Input Selector (Diffrentialx1 single endx1 single end with MicAmpx1)
- ADC S/N: 96dBA, S/ (N+D): 88dB
􀂆1ch ADC2
- Sampling Frequency: 8kHz~48kHz
- ADC S/N: 89dBA, S/(N+D): 82dB
􀂆4ch DAC
- Sampling Frequency: 8kHz~48kHz
- DAC S/N: 107dBA, S/ (N+D): 92dB
􀂆Microphone Interface
- Differential or single-end input
- Programmable Gain (+33dB ~ +15dB and 0dB, 3dB step)
- Low Noise Microphone Bias
􀂆Automatic Power Down (CODEC, DSP)
􀂆μP I/F: SPI, I2C
􀂆Power supply
Analog (AVDD): 3.0V ~ 3.6V (typ.3.3V)
Digital1 (DVDD): 3.0V ~ 3.6V (typ.3.3V)
Digital2 (DVDD18): 1.7V ~ 1.9V (typ.1.8V)
􀂆Operating temperature range: -40℃ ~ 85℃
􀂆Package: 48pin LQFP

图1.内部框图

图2.内部DSP框图

采用AK7757评估板参考设计
The AKD7757-A is an evaluation board for AK7757, which is a highly integrated digital signal processor with an integrated 4ch DAC, a stereo ADC with input selector, a mono ADC and an integrated digital audio interface. This board is composed of a main board and a sub board. The AKD7757-A can be set-up by a PC via USB port. RCA connector is used for both input and output of the analog signal. Digital audio interfaces are also integrated, enabling to Interface with a digital audio system via optical connectors or SMUX-PORTs.

AK7757评估板参考设计的主要特性
􀂆Read/Write access to PRAM, CRAM, OFREG and registers of the AK7757
􀂆Compatible with 2 types of digital audio interface
- Optical input (x1) / Optical output (x1)
- 10pin header for interface with external data source (x2)
􀂆ADC1 6ch input (differential input 3ch, single-end input 3ch), ADC2 1ch input, DAC 4ch output
􀂆USB port for board control

图3.参考设计框图

图4.参考设计原理图（1）

图5.参考设计原理图（2）

图6.参考设计原理图（3）

图7.参考设计原理图（4）

图8.参考设计原理图（5）

图9.参考设计原理图（5）

图10.参考设计原理图（6）

图11.参考设计原理图（7）

图12.参考设计原理图（8）

图13.参考设计原理图（9）