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ADF4350 charge pump current - unwanted hopping

Question asked by Miko on Feb 14, 2011
Latest reply on Mar 10, 2011 by Miko

Hi

I would like to ask about charge pump current setting. My Rset = 4.7k and tolerance is 5%. I observe let's say unwanted hopping of generated frequency. It means that that VCO lock on frequency lower than diserable. But from time to time switch to this desirable. Difference between desirable and obtained is 2xREFIN frequency. Unfortunatelly I didn't measure Vtune signal shape, but I wondering about charge pump current settings. It looks that Icp can be about 5.4 mA. Is it too much? Lock Detect pin is stable high.

 

Below some calculations from ADIsimPLL.

 

Best regards

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