ADF4355-3 has spurious at 1.8kHz

Question

Sir: 
 Our board output of ADF4355-3 has spurious at 1. 8kHz. The spurious is constant in different output frequency, bleed current and CP current. 
 We attempt to replace DC-DC with external power supply，but the spurious still unchanded. 
 We have a few questions: 
 1. Why and how to eliminate the spurious. 
 2. Why and how to Increase output power. 
 The specific register configuration and spurious is shown in the figure below

ADIApproved · Accepted Answer

Hi, 
 Negative bleed should be disabled in integer mode. 
 Also, I see that you are using evaluation board. I want to make sure that your on board VCXO is disabled and disconnected from the reference trace. Also, reference input mode is set as differential, is your 10 MHz reference signal differential or single ended? 
 Regards, 
 Kudret

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ADF4355-3 has spurious at 1.8kHz

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