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AD9547 frequency jitter

Question asked by CannaGiu on Dec 23, 2015
Latest reply on Jan 27, 2016 by CannaGiu

I'm using the AD9547 in my application and I've noted a jitter at low frequencies (around or below 1Hz), that impacts on my final application.

I've compared my application against the evaluation board (I've the AD9548 eval board but the parts are pretty the same) and on eval this problem not exist. (See the picture below: the blu trace is the eval output and the yellow my custom board.)

SCREN025.GIF)

The AD9547 runs in free run mode.

I'm using the same configuration on both platform (custom and eval) 40MHz XTAL as sysclk input and 1GHz PLL clock. The output 1 us 40MHz and output 2 10MHz.

The registers setup are the same (See attached file). I've check phase noises and are quit the same (except lower frequencies). I've tried to change and filter power supplies.

Anyone have an idea on what I can check?

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