calibration of ADF5610

I carefully read the datasheet of ADF5610 recently but the autocalibration part of ADF5610 confused me a lot. Every time after we write a frequency that we desire, what principles does the FSM follow to select subbands? Is it the sub-band where the desired frequency is exactly at its center? Looking forward to your reply.

  • +1
    •  Analog Employees 
    on Jan 22, 2021 10:50 AM

    Hi,

    During autocalibration the following steps take place:

    1. For desired RFOut, the subbands are searched to determine the subbands that contain the RFOut frequency. 

    2. Since subbands contain overlapping frequencies, RFOut may be within 2 consecutive subbands. 

    3. The FSM determines which one is most suitable by using the internal temperature compensation circuit as an input. e.g. if temperature is currently low (-40C), the subband is selected that requires the lower Vtune voltage. That way, if temperature increases, then Vtune has more range to increase within that selected subband. Also if operating temp is high then the band with higher Vtune is selected. As when temp is reduced, Vtune can be reduced within the band. 

    4. If temperature increases so that the desired RFout is beyond the operating subband, then this results in loss of lock. If automatic relock is enabled (Register 0x07, Bit 13 = 1), then when the subband changes it attempts to lock once more in the new subband.