Original: AK4688: 24-bit stereo audio solution integrating 2-channel ADC and DCA

AKM’s AK4688 is a stereo audio codec. The integrated ADC and DAC interfaces accept up to 24-bit input/output data and support asynchronous operation. The input range of the preamplifier can support line input and can be adjusted by an external resistor. A 2Vrms output ground voltage is obtained through an integrated charge pump, and a single 3.3V power supply reduces external parts such as AC coupling capacitors and mute circuits. The ADC module of AK4688 can obtain 99 dB of dynamic range, while the DAC module can obtain 105dB of dynamic range. The AK4688 is suitable for digital recording systems, digital TVs, Blu-ray recorders and home theater systems.

AK4688 main features

• Asynchronous ADC/DAC operation

• Capless stereo preamp, line in/out

• 24-bit stereo ADC

– 64x oversampling

– Sampling rate up to 48kHz

– Linear phase digital antialiasing filter

Figure 1 Internal block diagram

Figure 2 Reference Design Block Diagram

– S/(N+D): 83dB

– Dynamic range, S/N: 99dB

– Digital HPF for offset cancellation

• 24-bit stereo DAC

– 128x oversampling

– Sampling rate up to 192kHz

– 24-bit 8x digital filter

– S/(N+D): 95 dB

– Dynamic range, S/N: 105dB

– De-emphasis filter

• High jitter tolerance

• External master clock input:

– 256fs, 384fs, 512fs768fs (fs=32kHz~48kHz)

–128fs, 192fs, 256fs384fs (fs=64kHz~96kHz)

–128fs, 192fs (fs=128kHz~192kHz)

• 2 audio serial I/Fs (PORT1, PORT2)

– Master/Slave Mode (PORT1)

–I/F format

Figure 3 Reference Design Schematic (1)

PORT1, 2: MSB, LSB aligned (16/24 bits), 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: 36-pin QFN

Evaluation Board AK4688 Reference Design

The AKD4688-A is an evaluation board for the AK4688, a single-chip 24-bit codec with a 2ch ADC, and a 2ch DAC. It can evaluate not only the A/D and D/A of the AK4688, but also the asynchronous operation characteristics. Additionally, the board can be easily connected to digital audio equipment via the S/PDIF connector.

Main Features of Evaluation Board AK4688

• Compatible with 2 types of digital audio interfaces

– Optical Input/Output (S/PDIF) and DIT/DIR (AK4118A)

– 10PIN interface header with external data source

• Independent power supply or regulated power supply

• 10pin header register control