• State
  • Replies 1 reply
  • Subscribers 30 subscribers
  • Views 42 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

Original question:

PCM5100A: PCM5100APWR

PCM5100A: MICROPHONE NOICE ISSUE

MICHAEL MICHAEL
Prodigy 20 points
Part Number: PCM5100A
Other Parts Discussed in Thread: PCM1808, PCM5100

Tool/software:

Hi

Our product's audio block diagram is as follows



We use a PC to verify the basic functionality of the channels.
For the MIC channel, we listen to the device through the PC and then hear the sound through the SPEAKER.

During this test, we can hear noise in the MICROPHONE channel, and the noise increases with the MICROPHONE dB Level.
The MICROPHONE and SPEAKERuse PCM1808 for I2S audio A/D conversion, which transmitted to PCM5100 for D/A conversion and sent to the PC.

The design as follows: this is for the audio bypass function.

Questions:

  1. Have there been any similar noise issues encountered by other RD when they using PCM1808 with PCM5100 for the MICROPHONE channel?
    Are there any countermeasures which can advice us?


  • 0
    TI__Intellectual 760 points

    Hi,

    How are you sending the analog signal to the PC? Also, where are you hearing the noise? If you hear the noise in the speaker, maybe try to listen earlier in the signal chain. Can you measure the signal with the computer after the ADC? 

    I am going to assume you are testing the noise by listening to recordings made on the computer after the ADC block after the microphone input. The input signal level of the microphone into the ADC can make a big difference in noise. The max signal level into the PCM1808 ADC is VCC + 0.3V, with a typical level of VPP input as 0.6Vcc. For a Vcc of 5V, that means the Vpp of the signal should average around 3V, and it should be centered around 0.5Vcc or 2.5V. Make sure your microphone is outputting around 0.6Vcc for ideal noise performance. 

    Let me know any more details about the system - what voltage is coming out of the microphone? How are you sending a signal from the PC to the ADC?

    Best,
    Mir