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Trouble running the ADAU1701 at 192kHz

Question asked by electrojim on Feb 7, 2015
Latest reply on Feb 8, 2015 by electrojim

I know I have to be doing something wrong here, but I've looked at all the relevant documentation and searched the forum, but can't find what I've overlooked.  I'm running Sigma 3.9, if that matters.


I've got the ADAU1701 MINIZ evaluation board hotrodded with an stick-on 49.152MHz oscillator running off the eval board's own 3.3V supply.  The oscillator output is fed into the MCLK pin on J7.  I have a simple project loaded and everything set for a 192kHz sampling frequency.  The project compiles just fine, and the project actually runs perfectly at 48kHz (even with a 192kHz sampling rate 'propagated'), but when I switch over to the higher clock rate, all I get is white noise and heterodyne whistles out at max level.  ReadBacks and meters on the schematic go nuts at the 192kHz rate too.  The clock waveform going into Pin 32 of the 1701 looks good, snappier than built-in oscillator's, a full 3.3V p-p rectangular waveform.  With the switch in the 48kHz position I see a 3V p-p sinewave from the internal oscillator at 12.288MHz.  I put some series resistance in there to make sure the outboard oscillator wasn't violating the 1701s input somehow, but no change.


I did this same thing on the evaluation board for the ADAU144x, and that works like a champ.  Where have I messed up?