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AD9914 phase control during ramp

Question asked by subhan on Sep 18, 2014
Latest reply on Aug 30, 2016 by qcchen

Hello,

        I have started using AD9914 evaluation board for my project. My aim is to generate a stepped frequency waveform(10M-100M) with a step size of 5MHz. The dwell time at each step frequency is 10usec. An external clock used of 10MHz is used. Internal PLL mode was activated through software and a 2.4Ghz system clock was generated (with a multiplier value of 240). The digital ramp mode was selected and above mentioned values are being fed to the ad9914 software. No dwell high was selected in the software. DRCTL pin was controlled by external trigger which has a  pulse repetition time of 5msec. The External trigger generated is being referenced to the same External clock. We could able to see the frequency changes starting from 10Mhz to 100 Mhz in CRO referred to the External trigger. I want to have the starting phase of each step to be the same (lets say 0 deg) and it should not vary from one to sweep to other. is it possible to achieve phase coherency at each step and across sweeps?. From my observation the phase value keeps drifted from one trigger to other. Any suggestion are appreciated.

 

Regards

Subhan

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