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LMX2594: Set Freq in KHz resolution using Partial Assist

arye nudelman
Intellectual 255 points
Part Number: LMX2594


Tool/software:

Hi 

if i want to set frequency in a resolution of 500KHz Step, Can i use the Table as it provided below in the document 

Streamline RF Synthesizer VCO Calibration and Optimize
PLL Lock Time

if i want to change from 7500MHz to 7500.5MHz but by using 7500000KHz to 7500500

can i use same formulas? as when we change in MHz resolution?

do i need to use more registers than the below that i use? is the writing order important?

Is my writing order below ok?

should i add more registers for accuracy ?

here is my writing for 7500000 by writing order 

0x4E00A4      (reg_78d)
0x2B0000       (reg_43d)     should i add writing to 2A (reg_42d)?
0x270001       (reg_39d)      should i add writing to 26 (reg_38d)?

0x250304       (reg_37d)
0x24004B       (reg_36d)   should i add writing to 22 (reg_34d)?
0x14C848       (reg_20d)
0x11012B       (reg_17d)
0x00241C       (reg_0d)

here is my writing for 7500500 by writing order 

0x4E00A4
0x2B0001         (reg_43d)     should i add writing to 2A (reg_42d)?
0x2700C8          (reg_39d)      should i add writing to 26 (reg_38d)?
0x250304
0x24004B        (reg_36d)   should i add writing to 22 (reg_34d)?
0x14C848
0x11012B
0x00241C

  • 0
    TI__Guru** 110680 points

    Hi Arye,

    Suggest install TICS Pro to help you develop the software.

    For example, with below configuration, to change the frequency from 7500MHz to 7500.5MHz, only the PLL_NUM has to update.

  • 0 in reply to Noel Fung
    Intellectual 255 points

    thanks i use it a lot

    i just wonder if my order of writing registers is ok and what i will need a better resolution, for example 1 khz, i.e. what is the highest resolution i can achive while using the above registers. would i have to add additonal registers and when ? if i need to change a 1 khz or 100 hz etc. 

  • +1 in reply to arye nudelman
    TI__Guru** 110680 points

    Hi Arye,

    resolution = fpd / PLL_DEN. 

    to change the frequency, write to those related registers, programing sequence or order is not matter but the last register to write should be R0 (with FCAL_EN = 1) .