I am using the AIC3254 in a new design, and have a significant noise issue.
For this scenario, I am only using the DAC side of the codec, with an I2S interface. I am using the secondary S_DIN through the SCLK pin, and using the primary BCLK and WCLK. I am running 48kHz sample rate at 24 bits. The audio gets through just fine.
After initialization, while the data on the I2S port is all zeros, the DAC is quiet. However, as soon as the data begin to be non-zero, noise begins within the DAC. Taking the I2S input back to continuous zeros has no effect, the noise remains. Once it starts, the noise is always present.
The noise is audible white noise at about -32dB, well above the advertised noise level, so even with soft music or voice audio, the noise is quite audible.
The DAC is configured for PRB_P8, although I have tried PRB_P1 with identical results. I am using PTM_P4 for the maximum S/N ratio. The RDAC and LDAC are both in single-ended mode going to LOR and LOL. The gain on both LOR and LOL is +0dB. The ADCs are powered off.
We are using the LDO (at 3.3v) for internal power, if that makes any difference. I do not believe that the issue is due to sigma-delta settings since the noise is in the audible range.
I have spent days trying to track the noise down, reviewing the configuration settings again and again, but with no success. I'm sure I'm missing something, I just need a pointer to help resolve the issue.
What can I do to get the S/N back into the 100dB range promised by the DAC?
Thank you,
EdA
