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Query about ADF4159 Sweep Glitch

Question asked by WayneQ on Nov 25, 2014
Latest reply on Dec 23, 2014 by WayneQ



I am using your ADF4159 for VCO sweeping and I am getting “glitches” on the charge pump output line at multiples of the PFD/4 frequency.

The image shows VTUNE (input to VCO) over a sweep over 5 intervals of pFD/4 as captured by an oscilloscope.

As can be seen, sometimes the VTUNE line shows a slight depression and other times it shows a large spike.


Some settings I am using:

R divider =0 (no double or divider)

PFD frequency = 100 Mhz (same as the reference).

Sweep is from 2.8125 to 2.9375.

dev offset is 0, dev word is 839, there are 50000 hops.

CLK1 is 0x01, CLK2 is 0x02.

This is a continuous sawtooth sweep with no delay.

CSR is enabled and phase detector is positive.

Negative bleed current is disabled.


Can you help me?