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AD9956 LO and baseband mod generation external VCO configuration

Question asked by cwz on Nov 13, 2015
Latest reply on Nov 16, 2015 by KennyG

Hi there,

 

I would like to use the AD9956 in the LO and baseband modulation generation mode. As per Fig 24 in the datasheet, I would like my VCO to generate ~2,5GHz tone. However, here is my question:

 

Few things to make sure if VCO output is 2,5G:

     1) I have to set R appropriately so that SYSCLK does not exceed 400 MHz

     2) I have to set N appropriately so that PLLOSC does not exceed 200 MHz.

 

However, to set the R and N values, I first need to program the registers of the AD9956. So if that's the case, before I successfully program this values, how will the PLL loop behave, and subsequently, how will my VCO output behave?

 

Thanks in advance!

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