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PCM5121: The actual gain is always bigger 6dB the settings

Yang Wang
Prodigy 385 points
Part Number: PCM5121

Configure the Digital volume through I2C, no matter configure 0dB、7dB、10dB…, and Analog Gain Control register is 0dB, but per calculating the gain with input voltage and output voltage, the actual gain always bigger 6dB than settings. So could is there any other gain control I ignored?

  • +1
    TI__Guru 53773 points

    Hi Yang,

    We will take a look at this tomorrow after the US holiday. 

    Thanks,

    Paul

  • +1 in reply to Paul_Frost
    TI__Guru 53773 points

    Hi Yang,

    A full scale input (0dBFS) would result in a 2.1Vrms output.  2.1Vrms is approximately 3Vpeak or 6Vpeak-peak.  The device uses a 3.3V supply to generate a -3.3V supply for the negative output range.  For that reason, it would not be possible for the output to be +6dB greater than 2.1Vrms, or the output would clip.

    Can you confirm the signal amplitude of your digital input and the analog output amplitude?

    Thanks,

    Paul