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TLV320AIC3204: Do you have any formula to calculate 0dBFS=?Vrms

Lee Bob
Prodigy 50 points
Part Number: TLV320AIC3204

Hi ,

I'm using TLV320AIC3204, in datasheet there can only find this "Input signal level (0dB) Single-ended, CM = 0.9V 0.5Vrms"

But I want to know if I use differential input with CM= 0.9V, which is the full-scale voltage (0dBFS)?

Do you have any formula to calculate 0dBFS= x Vrms ? Both input and output.

Thanks.

  • 0
    TI__Guru* 84915 points
    Hi, Lee,

    The Full-Scale Voltage depends of the CM voltage and the kind of input/output. All the datasheet specifications are made for a single-ended input as you found. In the case of the differential input/output, the full-scale voltage is duplicated. For example, in your line above, the full-scale voltage would be 1Vrms for a differential input.

    "Input signal level (0dB) Differential, CM = 0.9V 1Vrms"

    Best regards,
    Luis Fernando Rodríguez S.
  • 0 in reply to Luis Fernando Rodriguez S.
    Prodigy 50 points
    Hi Luis,
    I tested on the EVM board. But I found about 2dB difference.

    Audio Source : 1kHz, 10mVrms=-40dBV
    EVM setup: CM = 0.9V, differential input on IN3L/IN3R, MIC PGA GAIN = 20dB

    The source is -40dBV, and the MIC GAIN is 20dB, so the record audio should be -40dBV+20dB=-20dBV.
    Because full-scale is 1Vrms=0dBV=0dBFS, the record audio should be -20dBFS.
    But I analyze the recorded audio file ,the Max level is about -22dBFS.

    There is about 2dB difference .
    Why does this happen? Dose it the attenuation on input route?

    Thanks.
  • 0 in reply to Lee Bob
    TI__Guru* 84915 points
    Hi, Lee,

    When the analog input is as low as 10mVrms, there could be risk of gain error. You may notice that if the analog input is near of the full-scale voltage, the PGA gain will be more exact. So, I would recommend to increase the analog input signal to have better results.

    Best regards,
    Luis Fernando Rodríguez S.