AD1938 bipolar operation

Hello !

I have a problem using the AD1938. In my actually project i developed a audio system which contains of a ADAU1446 and multiple AD1938 handling the analog world. The product is running fine exept of the on and off pop ups. So my question has anyone a idea how i can get my system booting up and going down without the on/off pop?

My first schematic is similar to the EVAL-ADAU144xEBZ. If it is helpfull i can send you a copy.

Later i changed the output ampilifier to a bipolar output stage using a Sallenkey-Filter, i hoped it will eliminate the DC-Bias and DC-blocking caps, but that changed nothing. In this case my idea were to boot up the hole system and after booting up, activate the output amplifier. This will not work because the feedback resistors in the output stage will route the DC bias to the output directly.

The problem is that i could not manage a bipolar operation with the AD1938!?

Has anyone a idea how i can manage the start up and power down without the popup? It is very important for this application to manage the boot and power down behaviour.

Thank you very much!!

Best Regards,

Moritz Bente

Audio Signal Processors

adau1446

ad1938

Integrated/Special Purpose A/D Converters

SigmaDSP Audio Processors

Audio CODECs

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