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ADF4107 problems

Question asked by cseppento on Nov 2, 2017
Latest reply on Nov 7, 2017 by cseppento



I scoured through the forum posts about this PLL but still couldn't solve my problems with the IC.

I am using it with a 50MHz quartz oscillator and my own microwave VCO (2.75-3.3GHz).
I am programming the PLL with an Arduino board and tried to verify its operation by checking
the various output options of the MUXOUT pin. It works fine when the output is set to DVDD or DGND
however the R and N counter output give interesting results.
The quartz oscillator works, I verified this with an oscillator probe, however the R counter output doesn't give anything.
Sometimes it does (after continuously uploading my program for the twentieth time or so),
but then the output frequency of the R counter is either 45kHz or 450kHz regardless of the R divider value
(in operation it will be set to 5, so I would like a 10MHz frequency at the output of the counter).
Most of the times however it doesn't give any output.  The N counter is similar, I tried to use an RF generator as input
instead of my VCO and regardless of the N value set (300,600,3000,6000) the divisor rate for a 2.8-3.2GHz input was constant
and the output frequency about 500kHz.
What could be the problem? I checked the quartz output and also my SPI clock on an oscilloscope, those seem to be fine,
so I ruled out the possibility that my measurement device was at fault.
I tried all three programming methods described in the datasheet and the PLL reacts fine to programming power-down as well
(I tried to debug what I could). The bias voltages at the REFin and RFin pins are good as well.
I also checked the handsoldered board and there do not seem to be any mistaken shortcircuits.
Furthermore I checked the things I could in the PLL debugging slideshow posted in other topics.

I hope that you may have some advice about what I am doing wrong and I thank you in advance for any insights.