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AD9957 DAC spectrum

Question asked by Alex_777 on Nov 30, 2015
Latest reply on Dec 1, 2015 by Alex_777

Hello.

I have my own ad9957 board (schematic is attached).

AD9957 is programmed in single tone mode.

Charge Pump Current 312uA.

VCO Band - 3.

Frequency Multiplication factor - 26

System Clock Frequency 650 MHz

 

I have the problem  with the  dirty spectrum near my signal.

Pll filter was designed with PLL_Loop_Filter Tool.

 

1) Open Loop Bandwidth - 100KHz

DSC_0005.jpg

 

2) Open Loop Bandwidth - 1.2 MHz (Narrow-Band View)

DSC_0008.jpg

 

Wide-Band View

 

DSC_0010.jpg

 

Please tell me, where there may be a problem ?

Thanks.

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