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HMC494LP3 self oscillation

Question asked by pawel_krzy on Jun 6, 2017
Latest reply on Oct 11, 2017 by MRichardson

Hello everyone!

 

I have made a design with HMC494LP3 divider. The design works well if I apply any signal to the positive input (I am using single input only). The problem with design starts when I turn off signal - the board is self osciallating.

 

I try to reduce this effect by adding additional resistor (between GND and negative input). The values which I try was:
 10k
 8.25k
4k
2.45k
50ohm
I tried with parallel capacitance and without it.

 

But the result was always the same - self oscillation at ~1.875GHz. I tried also to remove this resistor completely and self osciations are still present, but at lower frequency ~0.9375GHz (two times less than with a resistor).

 

Can You help to find me where the problem can be?


 - I am sure the problem is related with this IC since when I have it DC blocked and when I remove capacitor before HMC494 self oscilations are present, and when I remove capacitor after HMC494 the oscialtions disapears. I can post a schematic or give any additional data if needed!

 

Since I am using only 1 output (negative one) I tried to terminate output with the AC termination or resistive termination, but it do not remove oscillations.

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