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LMX2582: LMX2582_SPI_Programming_Dynamic_Frequencies

Part Number: LMX2582


I'm Currently using LMX2582 (Our Custom Designed Board) for PLL, and I'm using microchip controller ATSAME54P20A for connecting to LMX2582 Board using SPI Interface.For generating various frequencies, i am using Texas instruments TICS Pro Software.By using this i am able to generate certain frequencies (REGISTER VALUES) and implemeted this in my code and I am able to lock the PLL at certain defined frequencies like 850MHZ, 950MHZ etc.

The issue here is we have a frequency range from (850 to 5500MHZ) with step frequencies of 100KHZ how to change the register values for generating desired frequencies like (850.1, 950.5, 5549.9 etc) because i can't hardcode all the frequencies range( REGISTER VALUES) in my code.If there is any formula or example code using spi to lock the pll for dynamic frequencies please share.Kindly go through this and give your support.


Ganesh B

  • Hi Ganesh,

    We don't have example code, the required formula can be found in the datasheet.

    You should be able to find the TICS Pro python script in below directory:

    C:\ProgramData\Texas Instruments\TICS Pro\Configurations\Devices\PLL + VCO\LMX2582

  • Hi Noel Fung,

    Thanks for Your Reply. Even though you have provided the formula i don't any clue how those 46 registers (R70 to R0) is Changing according to the frequency.Suppose for example if i want to generate frequency for 850 mhz (46 registers values  are generated),the same way if i generate for 1000.1 mhz(46 registers values are generated) if there any single formula i can apply that will be applicable for all different frequencies. Because i have a frequency range of (950-2000 MHZ) 1050 Different frequencies with step frequency of 100KHZ total 10500 Different frequencies.

    I am programming using ATSAME54P20A using SPI. Please tell the logic or give some example to program these many (10500) different frequencies without hardcoding (46 registers for each frequencies). Also give how to automate the python script to generate 10500 different frequencies from (950-2000MHZ).

    Is it possible to generate frequency automatically for example i want generate frequency from 950 to 2000 mhz with step frequency 100khz (like 950.1,950.2,950.3 andson to 2000mhz. I will feed the frequency,export the register values and again feed the frequency and export the register values like fully automated.

    Thanks & Regards

    Ganesh B

  • Hi Ganesh,

    After Vcc power up or a reset, we need to program all registers. After that, we only need to program those registers that need to change to suit for the application need. For example, if we want a divided output, we simply need to program the divider registers. If we want to change the VCO frequency, we may need to program PLL_N, PLL_NUM and then program R0 to trigger a VCO calibration.

    You need to develop the software to do all the calculation with the equation I attached in this thread. The python script provides an example how to do this.