TI AIC31 Codec

Anyone here used the TI AIC31 Codec before? We are having some trouble with noise in the output. On a scope the noise looks broadband and fairly high level at about 250 mVpp. I have put the output on a spectrum analyzer and it is mostly above 100 kHz with a few tones, one at 28 kHz. Even though this is just voice, we have a spec of -50 dB relative to the max output for any noise up to 32 kHz. So at -40 dB, this tone is an issue. Further we can hear noise in the output when we hook up a speaker. The spectrum analyzer is not very good at lower frequencies and the zero input floor rises up to within 20dB of the max signal. So I am looking for another piece of equipment in the meantime that will show this range with better sensitivity.

Anyone else worked with this part? Did you see similar issues? The data sheet shows -100dB to the noise floor which is far below what we are seeing. The FAE says he does not expect a tone at 28 kHz. Of course we have been looking at our board for problems, but we also see this tone on the AIC31 eval board, but at 10dB reduced level. We even tested in a different lab just to make sure we weren't picking up something in the lab. This is getting a bit frustrating.

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rickman
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