Hi there, how are you?
I developed a product using two ADAU1401s, and each one has its own crystal. We never had any problems whatsoever with the many prototypes using good quality crystals. Unfortunately, the production from China used crystals with higher tolerance, and we get a pretty nasty background noise in many of them.
The problem completely disappears if I force sync between the crystals, or, if I supply both ICs with the clock from the same crystal. I know it is far from adequate, but we really need an immediate solution not to loose the entire batch.
1) Place two wire jumpers, being one between MCLKI and MCLKI, and another between OSCO and OSCO, thus forcing sync.
2) Remove one of the two Xtals, and supply both with the same clock by placing one wire jumper between OSCO of the DSP that has the Xtal and MCLKI of the DSP that doesn't have the Xtal.
Both tested and worked fine, still I would like to know which solution would be "less bad"...
UPDATE: With solution number 2, I still get a healthy 3Vpp clock, so I suppose the oscillator output has decent drive capability.
Please let me know, I really appreciate your input!