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PLL Problems Occurring During Temperature Test (ADF4106)

Question asked by PGS1029 on Aug 10, 2018
Latest reply on Aug 14, 2018 by Viktor_Vojta


We used the ADF4106 to output 1950MHz.

During the temperature test, when operating from room temperature to low temperature (+ 25 ° C -> -33 ° C, 2  ° C/min), the following phenomenon occurs.

In the PSA spectrum, TRACE2 was MAX HOLD and it was observed that small noise was generated during operation. During operation, no external CLK other than the power source was entered.

Attached photo 1 is LOOP FILTER BW 58KHz / Phase margin 68deg

Attached photo 2 is LOOP FILTER BW 70KHz / Phase margin 58deg 

OP AMP was used as the AD8610.

I changed the loop filter to see that the frequency was slightly reduced, but I want it to disappear completely.

Please let us know what caused the phenomenon and how to solve it.