Hi,
we are using the TLV320AIC32 Codec in order to generate audio for a loud speaker and noticed that some white noise was present at the output. After some investigation we discovered that the noise appears to originate from the codec DAC and is subsequently amplified by our gain circuit.
While performing tests, we observed that the noise is not present when the codec is initially configured and only appears once a non-zero digital input is supplied to the codec. Prior to the activation of the audio input, the noise level is measured at ~30dB less than what can be measured after audio has been applied and removed from the input. Changing the power state of the DAC (performing a power-down/power-up operation in the DAC Power and Output Driver Control Register) seems to return the DAC to the same level as after initialization, however using registers to momentarily disable the DAC is ill suited to the application in which the codec will be used.
Is there a way by which we can decrease the noise generated by the DAC when it is activated or a way by which the output of the DAC can be automatically disabled when a digital silence is received at the codec, attenuating the noise between activation ?
Here is the output of the codec after configuration (or after a DAC power-down/power-up operation) :
Here is the output of the codec after digital audio has been applied and removed from the input :
thanks,
Vincent
