• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 30 subscribers
  • Views 206 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

PCM1822: PCM1822IRTER audio noise floor goes high

jordan Lee
Prodigy 10 points
Part Number: PCM1822


Tool/software:

Hi Officer,

We use PCM1822IRTER as ADC, and my audio source is single-ended. (During the experiment, the audio source comes from the laptop AUX, and AUX_L_GND and AUX_R_GND come from the laptop's AUX's GND pin).

We have encountered a problem. If the power and audio source both come from the laptop, the noise floor is high. However, if the power and audio source come from different sources (for example, the audio source comes from the laptop and the power comes from the power supply), there is no noise floor problem. Could you expalin to this topic about what is root cause and how can we solve this problem when the power and audio source come from the same source? Thank you.

  • 0
    TI__Mastermind 27710 points

    Hi Jordan,

    A couple potential root causes:

    • There could be a ground loop issue inducing unwanted noise. The laptop's ground can carry switching noise from internal circuitry which gets coupled into ADC input
    • Power supplies from laptops can be noisy (especially USB power) and digital noise from the power supply can be injected into the audio signal.

    You're not seeing this issue with External power supply because they are typically cleaner sources.

    A potential solution is to:

    • check is AGND and DGND are separated or connected properly at a single point to minimize the current path between AUX_R and AUX_L.
    • Add ferrite bead on supply rails or a LPF