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Original question:

PCM1808EVM: Distorted signal

PCM1808EVM: Confusion about allowed input voltages

EliC
Prodigy 40 points
Part Number: PCM1808EVM
Other Parts Discussed in Thread: PCM1808,

Hi,

The datasheet states that a single-ended voltage input of 3 Vpp is allowed. The absolute ratings for the analog input voltage V_in_L, V_in_R are stated as follows:

Minimum: -0.3 V
Maximum: (VCC + 0.3 V) < 6.5

Does this mean I need to make sure my input audio signal is always abov3 -0.3V?
When I have for example a 3 Vpp audio signal do I need to DC offset it by +1.5 V so it alternates between 0 and +3 V instead of alternating between -1.5 V and +1.5 V?

Thanks

  • +1
    TI__Prodigy 220 points

    Hi,

    You do not need to apply any DC offset to your audio signal.

    Page 19 of the datasheet shows a typical application of the PCM1808. On the same page, there is a chart which says the analog input voltage range is 0 Vpp to 3 Vpp. Also, the schematic of the PCM1808EVM (page 8) shows 1uF blocking capacitors on both inputs, implying the PCM1808 input pins want the DC component decoupled from the incoming signal.

    An inputted 3 Vpp sine wave would be encoded as full scale (-0 dB).

    Hope this helps!