PCM1808: 0V centered audio input signal clarification

Steven Schlax

Part Number: PCM1808

I cannot find a definitive answer in the datasheet, but is it correct to follow the example application for a 0V centered audio signal? Can a 0V centered audio signal be input directly into the L and R input pins? Or is DC biasing of the signal necessary? If DC biasing is necessary, can the Vref pin be used for this?

over 7 years ago

0 Steve-Wilson over 7 years ago

TI__Mastermind 30250 points

Steven,

No the input signal cannot be 0V centered. That would violate the ABS max of the input.

There is a DC bias on the input pins which is in the data sheet as well:

best regards,

-Steve Wilson

0 Steven Schlax over 7 years ago in reply to Steve-Wilson

Prodigy 50 points

What about this post https://e2e.ti.com/support/audio/f/6/t/697417?tisearch=e2e-sitesearch&keymatch=PCM1808 ?
This seems to suggest there is internal biasing? And what is meant by "there is a DC bias on the input pins as well"?

0 Steven Schlax over 7 years ago in reply to Steve-Wilson

Prodigy 50 points

Ah I think I understand. 2.5V is mounted on the input pins, so in the presence of an AC coupling cap between the signal source and the input pins, the 0V centered audio signal will modulate on the 2.5V of the input pins through the AC coupling cap such that the audio signal is now centered on 2.5V? Is this the correct line of reasoning?

0 Collin Wells over 7 years ago in reply to Steven Schlax

TI__Guru 65015 points

That's correct! PCM1808 is a nice audio ADC and hopefully works well in your application.

0 Steven Schlax over 7 years ago in reply to Collin Wells

Prodigy 50 points

Understood, thanks Collin and Steve! And yes it has served me well. I originally had a more complex design to ingest the audio and this will simplify things a lot.

Regards,
Steven

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PCM1808: 0V centered audio input signal clarification