PCM1809: How to achieve ADC synchronous acquisition with 4 PCM1809 chips?

Part Number: PCM1809

Tool/software:

In the design, we want to use 4 PCM1809 ADCs to form an 8-channel ADC for data acquisition. Is there any solution that can enable the 4 ADs to synchronize data acquisition? The current solution we have in mind is to use one of them as the controller mode, and transfer the FSYNC and BCLK generated by it to the other 3 Target mode chips. Can synchronization be achieved? Or are there any other synchronization methods or reference documents or cases?

  • Hi Shaopeng,

    Yes this is possible. This scheme makes sense. However with one device as the controller, I think that the target PCM1809 devices will be delayed behind the PCM1809. I would either run all devices as target and use your I2S controller as the host, or add a delay to the PCM1809 data in your SoC.

    Best regards,
    Jeff McPherson

  • Hi Jeff McPherson,

    Thank you for your reply.

    1、At the beginning of the design, I thought about this plan, which uses all PCM1809 as the target mode to solve the synchronization problem of four PCM1809 in a single instrument. But we also need to synchronize between instruments, as mentioned in the manual as shown in the figure.

    I want to synchronize two instruments by stopping and generating the same MCLK. So the one PCM1809 that comes to mind is the controller, and the other three are the targets, with the aim of synchronizing various instruments by stopping and generating the same MCLK.

    2、You mentioned above that PCM1809 with three targets will have a delay compared to PCM1809 with one controller, and I cannot find relevant information in the manual. I have always believed that if the FSYNC between PCM1809 is the same, it can be synchronized. Is there any manual that mentions this aspect?

    Best regards,

    Shaopeng Liu

  • Hi Shaopeng,

    I understand your point. I think having all 4 devices be a target device would be lower risk for any synchronization issues, but as long as the devices are close together (less than many meters) I think this is okay.

    To your first point, you can also achieve the same synchronization using the FSYNC/BCLK clocks. See the paragraph from 6.4.1

    "In active mode, when the audio clocks are available, the device automatically powers up all ADC channels and starts transmitting data over the audio serial interface. If the clocks are stopped, then the device auto powers down the ADC channels."

  • Hi Jeff McPherson,

    Thank you very much for your reply. It has solved our problem.

    Best regards,

    Shaopeng Liu