TLV320AIC3106EVM-K: Mic input poor response

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Replies: 3

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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??

3 Replies

  • Rakesh,

    It appears that something is incorrect with the setup, let me ask you a few more questions and we can try to get to the bottom of this.

    can you provide your register configuration? are you using the EVM to aquire the audio via USB? or are you connecting another analyzer to the external I2S ports on the USBMOD-EVM?

    any additional information would be helpful.

    best regards,
    -Steve Wilson
  • In reply to Steve-Wilson:

    How to capturevregister configuration??..... yes i an acquiring audio using USB

  • In reply to Rakesh Muralidharan:

    Hi,

    As you said there was an issue with the setup,test results for Ti(1).xlsx the ground connection was flimsy . Now I have resolved the issue and captured data.

    Setup

    • Input source from audio analyzer
    • 1kHz tone , sine wave input. 600Ohms impedence, Unbalanced
    • Data captured using USB
    • Sampling frequency = 44.1kHz
    • PGA gain set to 0db
    • Level 0db
    • MIC3L input
    • No mIc bias

    Data sheet claims to offer dynamic range of 91db. Attached is my result.

    What is the level for full scale?? is it 200mVp-p.

    during my observation from test result 3660.test results for Ti(1).xlsx i could observe a drop in SINAD for input voltages above 200mV. This as i understand is due to increase in harmonic components. upto 200mV SINAD was good.

    how to obtain the aforesaid dynamic range. If i consider 200mV as my distortion less peak signal my dynamic range is about 70dB. There is still plenty of room for improvement.

    PLease let me know the fullscale for codec and reason for distortion above 200mV is it expected?? Please let me know