ADAU1961 high frequency noise issue

Hi Sir.

We had automotive infotainment project got high frequency noise issue.

Signal Chain is AUX input => ADAU1961(Pin 6 / Pin 14) => I2S => ADAU1451 => PA.

About high frequency noise issue please listen from below website.

We try LDO power alone to ADAU1961 and removed C899 / C900 the situation is same.

We also try AUX input to GND. But no any change from noise issue.

We used SigmaStudio to turn off ADAU1961 ADC Then no any noise.

We have no idea about the problem of noise currently. Please kindly help us to Solve this problem.

http://pan.baidu.com/s/1o7BhdUE

    •  Analog Employees 
    on Apr 14, 2016 4:40 PM over 4 years ago

    Hello AJ9520,

    This will take some time but I think it will turn out to be a PCB layout issue and a grounding issue. I see you are using two grounds. The power supply for the AVDD is on a different ground from the AGDN of the 1961. This is a problem.

    I would like to know more about your PCB layout and your PCB stackup details.

    My responses may be delayed because we are having a big internal conference this week and that is taking most of my time.

    Dave T

  • Dear Dave.

    Thanks for your reply.

    I tried to modify the PCB layout(Input by pass) / Power / GND then have not any changed about the noise.

    I will try to use sigma studio control ADAU1451 DSP function to solve this problem.

    If any more question I will let you know. Thanks for kindly help.

    •  Analog Employees 
    on Apr 20, 2016 5:56 PM over 4 years ago

    Hello AJ9520,

    I also noticed that you have the switching regulator on a different ground from the DSP. The grounds are linked using a cap and an inductor. You must tie these grounds together but just connecting them now may not make much difference because it really needs to be one solid ground plane. You did not mention the PCB stackup you are using. What I am looking for is that you have at least four layers with the internal layers being a power and ground plane.

    Then how the bypass caps are connected to the part and the planes is important along with the location of the caps. So show a picture of your layout around the DSP.

    Thanks,

    Dave T

  • Dear Dave.

    Thanks for your remind. I will take note and follow up.

     

    We are use sigma studio control ADAU1451 DSP function. Looks can solve this problem.

     

    Thank you for your detailed explanation.

     

    AJ