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Original question:

PCM1808-Q1: definition of "Center voltage Input range"

PCM1808-Q1: Center voltage input range

Shinji Tsuji
Genius 12668 points
Part Number: PCM1808-Q1
Other Parts Discussed in Thread: PCM1808

Hi team,

I asked about center voltage input range and got answer as it is Vref range.

But I found following thread explaining it us not Vref tolerance.

https://e2e.ti.com/support/audio-group/audio/f/audio-forum/1042724/pcm1808-q1-about-center-voltage-input-range

Could you give me a clear definition of the "Center voltage input range" in PCM1808-Q1 datasheet?

I would like to know if input signal below 0.2Vccc or above 0.8Vcc input to the device.

regards,

  • 0
    TI__Mastermind 18905 points

    Hi,

    the PCM1808 can be used in two input configurations. 

    1) DC blocking capacitor in series with the input - In this case the device self biases the inputs at Vref (0.5Vcc)

    2) No DC blocking caps on the input - In this case the input pins need to be biased at a center voltage(externally) within the range 0.2Vcc -> 0.8Vcc.

    If the center voltage on the input pins is outside of the specified range (0.2 Vcc - 0.8 Vcc) I suspect the front end amplifier would be in a non-linear region, and that THD+N performance would be worse.

    Regards,
    Arthur

  • 0 in reply to Arthur Brown
    TI__Genius 12668 points

    Hi Arthur,

    Vcc=5.0V, center voltage is biased externally to 0.2*Vcc=1V.

    In this case, 0.6*Vcc=3.0Vpp exceeds the analog input range of the device, correct?

    Input can be rail to rail?

    regards,

  • +1 in reply to Shinji Tsuji
    TI__Mastermind 18905 points

    Hi Shinji,

    Yes, regardless of the center voltage, the maximum analog input voltage should not be exceeded

    Regards,

    Arthur