Increase in HISS noise level

The ADAU1701's OSCO pin is not intended to be used as a clock output to drive the input clock of another IC. Please see the pin description on page 10 of the ADAU1701 datasheet. Running a trace to the other ADAU1701s on your board will increase the crystal oscillator circuit's capacitance and will affect the performance of the oscillator. If you look at the clock oscillator signals with an oscilloscope, you'll see that these are not clean digital signals, but rather something closer to a sine wave. This is not a good signal to send to other ICs as a master clock input.

The best solution for this is to use an external clock oscillator with a digital output as the input to all three ADAU1701s on your board. This will ensure that all three ICs receive the same quality clock and you'll likely have less problems with jitter or other issues with your clock signals.

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