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ADF4350 Unlock and Current Variation of Power Supply

Question asked by WayneQ on Jan 4, 2012
Latest reply on Jan 5, 2012 by rbrennan

The 1090MHz PLL is locked well by external SPI programming. But the 1030MHz designed PLL didn't locked to 1030MHz while trying to program the PLL by externally by SPI lines.


The PLL output frequency of 1030MHz and 1090MHz are generated by 20MHz reference Clock.


For the current variation of +3.3V power supply, We have found that the current variation of our +3.3V supply is due to the 1030MHz designed PLL is locked and unlocked continuously for multiple output frequency like 1060MHz , 1080MHz , 4GHz , 3.3 GHz, etc..


The above case is happened while 1030MHz PLL SPI Lines  CLK, DATA, LE are floating condition. The PLL is programmed automatically programmed to random frequency without external SPI programming (we don't have EEPROM and MC in our board, external programming is the only option for PLL Programming). By trying to program this PLL by External SPI lines, PLL is not locked and the PLL current consumption also didn't increased while trying external programming.


But this case is not happened in 1090MHz PLL.


Kindly suggest a solution for the above problem to proceed further.

Thanks and Regards