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TLV320AIC3106EVM-K: Mic input poor response

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Replies: 14

Views: 527

Part Number: TLV320AIC3106EVM-K

Hi,


I have procured an evaluation board of Tlv320aic3106.

I will be attaching a coil mic to it and expect to sample at a rate of 8kHz. I have checked the output range of my coil mic (2mV to 10mV) Vpp.
AUDIO CODEC DATA ANALYSIS.docx I fed to mic input (MIC3R) to EVM  using audio analyzer(set to 600Ohms,1Khz tone,sine ). Other pin grounded.
I acquired samples (sound recorder in Windows 7) using PC in .wav format.

following were my configurations for codec to capture input
MIC3R input on audio codec (LADC active) 
Level (attenuation set to 0db)
PGA set to 0db

Sampling freq default 44.1kHz



and fed following range (3mV to 500mV) 1kHz tones.

On analyzing the captured input. Results attached ....I can receive 50mV  with wave shape maintained as shown in doc ..... below 50mV inputs waveshape looks unrecognizable negative swing missing....
Applying 500mV gives a clear swing, for lower voltages (below 50mV) no much negative swing seen....For 500mV SINAD is low

I tried applying  PGA of 20dB to lower voltages 3mV to 50mV here to lower voltages though receive higher amplitude has no tone content for voltages below 50mV.

I later modified the input with low pass filter of 4kHz bandwidth but of no use.

I am unable to identify what is the issue. Is this noise inherent at chip input?? Chip data sheet points to a dynamic range of 91db.Is it board induced noise overcoming weak input signals.??

Does it mean I need to amplify the signal before sending to codec??

  • In reply to Steve-Wilson:

    ADC clock configuration.docxDear Steve-Wilson

    Sorry for late reply.

  • In reply to satheesh kumar32:

    Hi steve
    This is in continuation to the above post. we have read back the register related to PLL configuration as explained by you in the previous post and register readings are enumerated below.
    r 30 02 1: AA
    r 30 03 1: 91
    r 30 04 1: 20
    r 30 05 1: 6E
    r 30 06 1: 88
    Expecting your reply.
  • In reply to satheesh kumar32:

    Hi Steave Wilson

    A gentle reminder

    Regards
    Satheesh Kumar S
  • In reply to satheesh kumar32:

    Satheesh,

    The issue here is that the USBMOD EVM is always capturing USB audio at 44.1khz. There are ways for us to test 8khz performance using the USB interface, but they require that we change the firmware on the USBMODEVM. This would then make the USBMOD EVM incompatible with the GUI. It would be compatible with other GUIs, so if you have the configuration it is no problem to do.

    This is the reason why you are getting poor performance, because your clock continue to run at 44.1khz, while your codec is running at 8khz.

    if you can use an external audio analyzer like an Audio precision, that would also work
    -Steve

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