AnsweredAssumed Answered

ADF4355 Unlocking when changing frequency.

Question asked by Osamu on Dec 10, 2017
Latest reply on Jan 8, 2018 by Brigid.Duggan



Sometimes locking is released when changing the PLL frequency.


Condition setting

Reference frequency: 10 MHz

Fout  Tx setting5.7575,7GHz Rx setting5,1445.104GHz

Loop Filter was designed with ADISimPLL.


Conditions for occurrence of defect symptoms

Appears at frequency down from 5.757 to 5.7 GHz at Tx frequency switching time. It also appeared in Rx.

Appears at 15~20 °C (using A constant temperature bath)

A problem was confirmed with 2/2 set and Eva-board.

Frequency of appearance is 1/200

Improve by changing the condition of ADCCLK.

Freq:    81kHz→98kHz→51kHz

Attachment: Spectrum analyzer waveform Lock / unlock


I want to know that Detailed function of the ADC in the PLL.

Especially how does it feed back to Vtune voltage?

Also, Why lock-out occurs?


Best regards