AnsweredAssumed Answered

MCLK rate fluctuating

Question asked by sydPringles on Jan 31, 2011
Latest reply on Feb 1, 2011 by BrettG

Hi there,

 

I'm running an ADAU1701 and have found that my MCLK frequency fluctuates.

Specifically, in master mode, the clock doesn't stay at one frequency. This is leading to a noisy I2S output. I've tried outputting a sine wave and the pitch changes, on top of having a high noise floor.

In master mode, I've also tried taking out the oscillator and used a function generator to generate the clock signal. Surprisingly, the result is the same. Scoping the generator output, I get a clean clock signal. But scoping MCLK from the chip, the frequency fluctuates.

 

Is this a known or common problem?

 

Thanks for any help or suggestions.

 

-- Garry

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